Don’t let supply-chain disruptions knock your projects off schedule – navigate roadblocks and stay on track

Originally published in Military Embedded Systems 

By David Kiesling

Every business – including those that supply the military-electronics arena – is feeling the pain of supply-chain problems these days. Many, in fact, are finding it impossible to run efficiently, meet demand, and deliver on time when necessary parts and materials are stuck in limbo.

Survival of the fittest

The current tight supply-chain situation is having a painful impact on many companies, slowing production as parts, materials, and labor become scarce. Whether you are waiting on products or services like installation and repair, deadline slippage is beyond frustrating. The delays can kill your revenue, cause you to lose loyal customers and new business, and damage your business relationships.

Planning for the long term might sound a bit ambitious when the more immediate problem is that today’s orders are stalled, so let’s start by discussing survival strategies for the current logjam.

Workarounds you can implement now

Decide first if your current suppliers can meet your immediate needs. Can you wait? If delays are seriously impacting your business, consider all your options. Not all products or suppliers are equally prepared to operate through a supply-chain crisis like this. Those with the lowest incidence of backlogs right now either laid the groundwork for resilience before 2020, or they pivoted quickly to prioritize supply-chain agility as the going got tough. The most successful probably did both.

Look around for alternate suppliers if you need to. You can minimize delays by working with the companies that can support your short-term needs more quickly than your existing partners can accommodate.

If you’re lucky enough to be getting what you need, when you need it, from your existing suppliers – consider placing or confirming orders and inventories as early as you can. That way, you won’t get left behind or caught short.

The long game

These challenges will light the way for successful organizations to prioritize resilience to grow and prosper in the future. How can you be better prepared for tomorrow, next month, next year? Survive the present, of course; protect your relationships and reputation as best you can, using the mitigation tactics discussed above. While you’re at it, consider long-term changes that will better position your company for whatever lies ahead.

Find partners with multiple production facilities worldwide; they can often move your work to areas where bottlenecks are less severe so that changing global challenges don’t shut off your supply. Different regions of the world are feeling COVID-19 impacts and shipping snafus at different times, so redundant geographic capabilities can alleviate regional pressures.

For example: Over the past few years, Times Microwave Systems strategically managed growth, preparing for a situation such as this by opening new manufacturing and warehousing facilities in China, India, and Europe. Moving production closer to customers allowed for shorter delivery routes and created more options for mitigating shifting labor and supply-chain issues. When difficulties arose, it was possible to maintain a steady inventory and supply of the products and services customers relied on.

Decentralized manufacturing capabilities enabled uninterrupted production throughout the pandemic, building inventory needed to meet immediate demand. By continually increasing on-hand stock for standard materials across internal and distributor-serviced warehouses, companies that prepared this way are now better-suited to weather the volatility in raw material costs, thereby resulting in more stable pricing for customers.

Flexibility and versatility should also be considered in business and supplier relationships. A company that offers custom solutions can work with you to develop the most feasible systems at the time. You can thus avoid getting locked into a one-size-fits-all system design that depends upon one source, one material, or one standard product that could be in short supply when you actually need it.

Watch out for false promises

Make sure you are buying genuine products from a reputable company to ensure your system works as it should. Shortages tend to bring counterfeits, fakes, and clones out of the woodwork, as unscrupulous operators look for ways to cash in on a crisis. The performance of your customers’ products depends on reliable product sourcing. Customers that unwittingly buy inferior products sold under false pretenses often pay the price with dismal system performance.

Moving through and forward

Do whatever you have to do to get through this crisis. Be flexible. Build resilience for the future. Work with organizations that are working through the current issues with minimal disruptions. And adjust your approach to qualifying the companies you work with so that you’ll be ready for the next uncertainty.

Adding new high-frequency capabilities to military avionics applications

By Ted Prema

Originally published in Military Embedded Systems

The high-frequency radio frequency (RF) interconnections within military avionics systems are essential components. They must perform repeatably and reliably and meet reduced size, weight, and power (SWaP) requirements. At the same time, the RF coaxial cables and connectors operating in these critical avionics applications have complex electrical, mechanical, and environmental requirements and must remain accessible for maintenance or troubleshooting.

Additionally, fitting these systems into very tight spaces can allow unwanted coupling between RF transmission lines such as coaxial cables. High-density, modular multiport interconnect systems can create a smaller, modular connector assembly. Such multiport connector systems integrate multiple coaxial connector contacts into a single housing for much higher interconnection density than individual coaxial connections.

Frequency requirements are rising

Today’s military avionics technologies, in­cluding intelligence, radar, collision avoidance, electronic guidance, navigation, electronic warfare, and communications, require higher frequencies to provide increased bandwidth for a growing number of complex subsystems. Military avionics systems that once operated at frequencies of 12-18 GHz are now extending into the millimeter-wave (mmWave) frequency range of 30 GHz and beyond.

High-frequency RF interconnects for military avionics systems must retain their predecessors’ lightweight and small form factors to fit the high-density requirements of modern airframes and avionics systems. Driven by reduced SWaP equipment requirements, avionics systems are being mounted within smaller airframes and equipment housings, requiring coaxial assemblies to maintain reliable electrical and mechanical interconnections in tight spaces and under the most severe operating conditions.

Such a compact modular multiport connector system provides smaller, lighter interconnections to support denser, more tightly packed avionics systems. By mating a single multiport connector rather than multiple separate coaxial cable assemblies, the single connector interface provided by multiport shells reduces installation time, can ease system maintenance and testing, and increase reliability.

Expand capabilities within existing infrastructure

Military avionics interconnect systems operate in harsh environments on a wide range of airframes, enduring high-shock and vibration; corrosive effects of fuels, hydraulic fluids, and other chemicals; vacuum-like conditions created by high altitudes; and wide temperature ranges. These military avionics systems must handle these challenging environmental conditions while packing greater functionality into smaller spaces. This requires new coaxial cables and connectors to deliver high signal integrity and reliability.

Critical considerations for RF interconnects for challenging avionics and airframe applications include:

• Lightweight: Weight reduction is critical to increasing fuel efficiency. Today’s frequency band requirements are also becoming more complex, creating the need for additional lightweight, small, high-precision RF solutions.
• High density: The increasing number of antennas in military avionics applications creates the need for more electronic boxes and their connections. Furthermore, new high-density solutions are required as frequencies increase and interconnect dimensions decrease to accommodate shorter wavelengths.
• Shock and vibration: When a connector attached to an antenna vibrates, as it will in flight, microphonic noise can impact the connection. This can cause interference in the signal transmission and errors for the RF system. Minimizing space between the cables and connectors is necessary for the interconnect system to survive the high vibration. Furthermore, this microphonic noise wears out the plating on the pins. Use of spring-loaded interfaces can all but eliminate this for both electrical and mechanical improvements.
• Temperature: Higher altitudes, speeds, and frequencies result in higher temperature requirements, making materials considerations more complex.
• Maintenance and access: Antennas mounted on the aircraft’s exterior are routinely damaged, and expedited repair of those antennas is essential. However, antennas are often difficult to access in many avionics systems, making maintenance and replacement very complicated and time-consuming.

Multiport shells such as the M8 multiport connection system are constructed from lightweight aluminum and have advanced reach/ROHS-compliant conductive platings tested to the most severe corrosion resistance requirements. (ROHS is a directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment.) The new contact designated M8M works up to 40 GHz and meets the needs of new high-frequency applications. The M8 multiport system has a a shielded structure to meet the electromagnetic interference and electromagnetic compatibility (EMI/EMC) requirements of densely packed military and civil avionics systems. The design also enables blind-mating interconnections. A spring-loaded design aims the parts for use in the harsh, high-vibration, environments typically found in military avionics applications. These parts are in service on a variety of U.S. and allied military aircraft from SIGINT/ELINT [signals intelligence/electronic intelligence] platforms to fast fighter jets.

Advanced military avionics electronics applications must accommodate extremely restricted space constraints and rising operating frequencies. A military avionics wireless system’s range that once operated between 12 and 18 GHz is now extending into the millimeter-wave (mmWave) frequency range of 30 GHz and beyond. High-frequency RF interconnects for military avionics systems must retain their predecessors’ light weight and small form factors to fit the high-density requirements of modern airframes and avionics systems.

Powering high-performance, ultrareliable RF systems in military electronics

By Ted Prema

Originally published in Military Embedded Systems

Radio frequency (RF) systems are used to power vital military electronics applications such as intelligence, surveillance, and reconnaissance (ISR) systems; communications systems; and electronic warfare (EW) suites. These systems must be extremely reliable and continually offer high performance – in very demanding, confined, and variable environments on the ground, in the air, and at sea. Each of these applications has unique requirements, driving development of custom RF interconnect solutions to address specific challenges. While safety comes first in the design of any of these complex military RF systems, performance must also be flawless.

For example, EW systems perform numerous mission-critical functions, including defense against attacks and providing enhanced situational awareness. These systems use RF signals to locate and identify potential threats, landscape features, and more, and include ground-based radar, antimissile defense, guidance systems, and similar applications. Each of these applications depends entirely on continuous real-time transmission of data with high accuracy.

Since these systems often operate under severe environmental conditions, two of the most important considerations in choosing optimal RF interconnect solutions include the use of low-smoke, zero-halogen cable and connectors and the use of assemblies optimized for high phase stability even at high temperature.

Optimizing for phase stability even at temperature

Fires are one of the most serious dangers in confined spaces such as in military aircraft, tanks, ships, and submarines. Fire can quickly fill an area with smoke, obscure visibility, and drastically impede safe evacuation. Toxic gases and the lack of breathable air add to the danger.

If a fire occurs in this type of confined space, it is crucial that the wiring and cables powering the RF systems do not give off toxic or optically dense gases when subjected to the high temperatures of the fire. Low-smoke, zero-halogen cable assemblies are therefore essential for passenger safety in spaces where air exchange is minimal. This is especially true in areas where densely packed cables are installed in proximity to humans or sensitive electronic equipment, which is why military users were one of the first adopters of low-smoke, zero-halogen (LSZH) standards.

The RF systems that perform critical operations in these environments must be designed to work as safely as possible within the application constraints. Under fire, a low-smoke cable (also known as limited-smoke cable) emits less optically dense smoke at a slower rate than a standard cable, enabling occupants to exit the hazardous area and protecting the safety of firefighting operations.

Halogens like chlorine, fluorine, and bromine are often used as effective fire retardants in wire and cables, enabling a cable to pass an industry flame test. However, halogens emit toxic gases when burning, so zero-halogen cables are another important requirement for military electronics systems. Halogen-free materials also produce clearer, whiter smoke for better visibility and do not emit halogen’s toxic off-gases.

Environmental challenges and phase stability

Phase is a key parameter for detection and measurement in many military RF systems such as radar, missile defense, EW, and many other systems that rely on continuous transmission and reception of RF signals with high accuracy and consistent speeds, regardless of temperature. The phase behavior of coaxial cable assemblies can adversely affect system performance when phase tracking is required and, as a result, phase must be extremely stable in the components within those RF systems.

For example, the electronically steered antennas used in many military RF applications use antennas with an array of radiating elements to steer antenna beams rather than physically moving an antenna. Beam-steering for transmission or reception is performed by adjusting the phase of the individual antenna elements in the array. The antenna array elements are each fed by high-frequency transmission lines; the accuracy of the signal phase presented to each array element depends on the phase accuracy and stability of the cable assemblies.

Military electronics systems are exposed to extreme and highly variable environmental conditions, such as corrosive salt spray in the ocean or high temperatures in the desert. For effective performance, the RF signals within those systems should travel through any coaxial cables with minimal delays and loss regardless of these environmental factors. As coaxial cables are subjected to cold and hot temperature extremes, their phase characteristics change as a function of temperature, with changes in the phase tracking or matching between cables. Even a small phase-tracking error between cables used in a phase-critical application, such as for a phased-array antenna, can adversely affect antenna performance.

Times Microwave offers PhaseTrack Low Smoke (PTLS) cable assemblies designed to meet the low-smoke, zero-halogen, and phase stability requirements of high-performance military electronics applications. The coaxial cable features a proprietary foam polyethylene blended dielectric called TF5. This innovative material provides exceptional phase stability with temperature performance to +85 °C and does not suffer the abrupt shift in phase that occurs with solid or tape-wrapped PTFE [polytetrafluoroethylene]-based coaxial cables. It eliminates the phenomenon known as the PTFE knee, in which the PTFE (also known as Teflon) undergoes a structural transition at approximately 18 °C that actually alters the dielectric constant of the material and substantially changes the delay of the transmitted signal. This nonlinear phenomenon is a property of the molecular structure of the PTFE material and cannot be eliminated regardless of advancements in dielectric manufacturing technology.

Offered as a complete assembly, the PTLS family of products are available in cable diameters from 0.2 to 0.6 inches, address all frequencies ranging from HF through K-band, and include an optimized version for minimum loss at Ku-band frequencies. The cables use a proven low-/zero-smoke, zero-halogen jacket.

To meet the demands of a variety of systems, these assemblies can also be supplied with any type of industry-standard RF connector or contact interface and be terminated with low-passive-intermodulation (low-PIM) 7-16, 4.3-10, or Type N designs and tested to an assured maximum PIM level -160 dBc.

RF cables and connectors for avionics balance size, materials

By David Kiesling

Originally published in Military Embedded Systems

Today’s complex frequency-band requirements – including 5G, new and upgraded satellite communications (SATCOM) systems, instrument flight procedure (IFP) systems using Bluetooth, and more – are creating the need for additional lightweight, small, high-precision radio frequency (RF) solutions. These systems operate at frequencies up to 90 GHz in some cases. The avionics industry needs low-loss, high-temperature, high-flexibility cable for navigation, collision avoidance, and communication systems in applications such as GPS, Automatic Dependent Surveillance-Broadcast (ADS-B), SATCOM, and air-to-ground comms.

Avionics applications also have limited space, as they accommodate more application needs throughout the vehicle. As frequencies increase and interconnect dimensions decrease to accommodate the smaller wavelengths, semi-rigid solutions have traditionally been used for these applications. However, these assemblies in very small sizes become fragile, making installation difficult and troubleshooting impossible.

Use of highly flexible, high-performance cable can be used in densely packed in-the-box applications; such flexible assemblies can be bent around tight corners and very closely behind the connector to minimize footprint, save space, and simplify cable routing in tight spaces. The flexible cable eliminates the need to protect the back of the connector and simplifies maintenance.

In flight, extraordinarily high vibration puts stress on the board hardware. Minimizing space between the cables and connectors is necessary for the interconnect system to survive the high vibration.

Taking a cue from commercial air innovations

Urban air mobility (UAM) is a concept for a safe and efficient aviation transportation system that will use highly automated aircraft to operate and transport passengers or cargo at lower altitudes within urban and suburban areas. Most UAM vehicles will operate below 10,000 feet, with battery power limiting their altitude and endurance. As the technology evolves, the density of UAMs in motion will increase, and in a scenario called “swarming,” their ADS systems will need to be in constant communication to avoid collisions. These systems are largely dependent upon antennas and high-frequency transceivers to enable the sensors to talk to each other, so a low-loss, reliable, low-weight cable is critical for reliable communications.

Further developments include advanced air mobility (AAM) solutions, which build upon the UAM concept with applications that will operate beyond urban environments, ranging from delivery drones to electric vertical takeoff and landing (eVTOL) applications. Like electric vehicles, eVTOL controls run on onboard electric power, and batteries are heavy, so weight is a substantial consideration. As a result, these technologies require advanced solutions to meet new requirements while adhering to the size and weight principles that have governed their predecessors for decades.

Avionics for UAVs

Another rapidly growing area of avionics are those for unmanned aerial vehicles (UAVs). Some UAVs are fairly simple and use a single data link, which requires a relatively simple RF interconnect solution. However, as hypersonics are introduced, some of these UAVs are as much as Mach 5, which adds high-temperature requirements into the mix. The higher the altitude, the higher the speed, the higher the frequency, the more complex the problem from a materials point of view. These issues can be addressed with dielectrics; moreover, there is the possibility of using quartz materials as dielectrics for hypersonic applications.

Ultimately, whoever is designing the structure needs to understand the environment, the UAV’s altitude requirements, what sort of longevity is required, how often maintenance is allowed, and what kind of test environment is available. For example, will the UAV carry electronic warfare (EW) systems or electronic intelligence systems, or is the payload  purely data links and video?

The right interconnect

A key consideration for avionics RF interconnections is the dielectric and how it behaves in that environment as it reaches a state of equilibrium with the surrounding environment. For example, an aircraft on the ground is fully loaded with air, while at flight altitude, more of a vacuum environment is created, with outgassing conditions for dielectric and other electronic materials. When the aircraft returns to the ground, the cable is fundamentally a vacuum. Any fluids or gases surrounding it will be absorbed by the dielectric, and they will recondense within it. At that point, the dielectric acts like a sponge: The only way to remove contaminants is to bake it. This is obviously not feasible inside an aircraft, so vapor sealing is also critical for high-end, high-performance, high-altitude applications.

So many factors must be considered in the design of the right RF interconnect solution. For example, polyethylene improves fire retardancy and flame resistance; it’s a really good cabling option for outdoor environments or for indoor environments with a fire-retardant, UL-listed jacket. A caveat: Polyurethanes can be significantly more flexible, but they cannot be used in a manned environment.

On the airframe side, PTFE (synthetic fluoropolymer) dielectric cables that tolerate high temperatures are typically used and can be combined with a higher-than-standard PTMP (polyester plastic) tape wrap that is very low loss. This type of solution can be used all the way up to 50 gigahertz or more. At the high end of the temperature spectrum, some silicon dioxide cables that are rated for up to 800 °C or more.

Connector optimization 

The ultimate goal is to optimize connectors for mechanical, environmental, and electrical performance, and make it very easy to install. A number of aluminum and plastic connectors are available to keep it lightweight.

Development work is being done on plastics, including threaded connectors, snap-line connectors, bayonet-style connectors and more, with materials like Delrin. Additional research and development is underway on an ultralight solution, including a modular connector solution with a plastic coupling and tooling solutions. This approach would help with maintenance, enabling users to fix problems directly in the field.

Tooling can ease assembly

When there is a need to install the RF interconnect solution aftermarket or perform maintenance work in the field, tooling is available that eliminates the need to use razor blades in the field, making on-site assembly safer and easier in what could be a contested area. This approach from companies like Times Microwave Systems enables everyone to use the same tool on the cable for the same application as opposed to the alternative, multiple technicians using different types of tooling and techniques.

Times Microwave Systems offers InstaBend (IB) 047, a compact, phase stable, highly flexible, micro coaxial cable. Originally designed for space flight applications, this high-performance cable easily accommodates densely packed in-the-box applications. For more information, visit www.timesmicrowave.com.

Key Considerations for Coaxial Cables in Space

Phase Stability

For phase-sensitive systems, compensating for the knee multiple times per orbit as the spacecraft moves through its operating temperature range is challenging and limits overall system performance. Other dielectrics such as Times Microwave’s TF4™ dielectric and Sio2™ silicon dioxide materials do not produce a similar non-linear change. In addition to controlling overall phase change vs. temperature, designers may need to characterize the hysteresis of the phase change across the operating temperature range. The silicon dioxide dielectric provides linear phase change with exceptional repeatability for applications requiring low hysteresis.

Return Loss

The second major environmental consideration for spaceflight applications is electrical performance over radiation exposure. Plastics such as PTFE and TF4 will degrade over time, increasing loss. For short-duration or risk-permissive missions, these long-term concerns may not be compelling. For long-duration, high-exposure, or high-reliability missions, using radiation-tolerant coaxial solutions such as the SiO2 line is better than shielding a plastic.

High Density

The high-frequency cables required for spaceflight applications have a shorter range, requiring a dense network of antennas.

Many different requirements may apply in terms of RF and microwave interconnects used with ground-based satellite dishes, such as high-frequency performance, low-attenuation needs, phase stability, and low-PIM performance. Our TCOM, MaxGain, and LMR products are designed to address these needs.

At the same time, technology providers are working on advanced designs that accommodate extremely restricted space constraints and producing spaceflight connectors that successfully operate up to 70 GHz. Our new InstaBend high-performance microwave assemblies provide a flexible preassembled design for interconnects between RF circuit cards, modules, and enclosure panels, enabling space-efficient implementation for higher frequencies.

The high-performance microwave assemblies are ideal for in-the-box applications because the cable can be bent very closely behind the connector. This minimizes footprint, saves room, and simplifies cable routing, eliminating the need to protect the back of the connector.

Materials

In addition to the issues of smaller cables tightly packed and connected, space applications require materials and constructions that withstand radiation, sandblast storms, extreme temperatures, and pressure variations. The latest materials technology and manufacturing processes are needed.

In the past, semi-rigid cables have been the standard cabling solution in space applications because their solid copper outer conductor protects the dielectric material inside. Today, special semi-rigid cable solutions based on silicon dioxide dielectrics are available. For example, our SiO2 cable assemblies are highly temperature and radiation resistant.

Some antennas fold into the satellite when not in use and unfold upon arrival at the satellite’s destination. There, the antennas will point to other satellites, get a position, and lock mechanically. Flexible cables are needed to work around the elbow that enables the antenna to fold and unfold.

Connectors

New styles of connector interfaces such as Times Microwave’s TLMP address the electrical and mechanical weaknesses of traditional high-frequency SMP/SMPM interfaces for high-vibration spaceflight applications. They visually indicate full engagement by exposing a green ring on the connector body when successfully mated.

Once routed correctly, it is also critical to ensure that the cable is appropriately mated to ensure effective RF performance. For threaded connectors, RF assembly suppliers should be able to provide recommended connector torque values. Designers should also consider multiport connectors that will mate multiple contacts simultaneously, reducing the opportunities for error.

Times Microwave Systems: The Ideal RF Interconnect Partner for Demanding Space Applications

Qualifications and Heritage

Our team has deep experience in space and other mission-critical industries such as military and defense.

Breadth of Products

Components deployed in space must meet many technical standards. There is, however, no standard for how to apply these materials to construct a consistently reliable RF solution. That is where our expertise and access to a full range of product options are needed.  You can select the suitable material and choose from multiple cable constructions, various connector designs, and assembly techniques, all from the same supplier.

Dedicated Technical Experts

The complexity of space applications requires an effective partner who will work collaboratively to extend your design team. We help our partners understand the electrical and mechanical trade-offs particular to their unique space applications. Our technical team asks the right questions and listens to understand your unique needs, always considering innovative solutions.

Attenuation

Three properties define the attenuation of a coaxial cable: the conductivity of the conductors, the dielectric constant, and the diameter of the cable. In general, larger-diameter cables provide lower attenuation per unit length than comparable smaller-diameter cables, but this comes at the cost of increased mass and a wider minimum bend radius. Larger cables cannot be bent as tightly as smaller cables, and an overly tight bend will cause the cable to become oblong or, worse, to kink, causing an impedance mismatch and excessive return loss. A primary decision for designers is to balance the contribution of cable loss to their RF link budget with the mechanical considerations for system size and mass.

High-conductivity materials such as copper and silver provide low attenuation per unit length but are often heavy or expensive. Lighter-weight materials such as stainless steel and aluminum reduce overall mass but are poor conductors. Cable manufacturers frequently optimize their conductor designs by cladding or plating a lightweight, low-cost base metal with higher-conductivity copper or silver for the RF path.

A lower-loss dielectric generally will be lighter because it incorporates more air into the media. More air in the dielectric material lowers the effective dielectric constant of the total media and brings the loss closer to the ideal performance of a wave traveling in a vacuum.

Click HERE to access the Attenuation Calculator.

Microwave Journal

Achieving High Density in Mission-Critical Circuits

By David Kiesling

Originally published in Microwave Journal

Technology providers are creating advanced new wireless system designs within restricted space constraints in avionics, 5G, space and many other industries. These applications rely on high density RF interconnections capable of high signal integrity and reliability in ever more miniature housings. There are many challenges to providing practical RF interconnections in such dense housing environments. Fortunately, innovations in RF interconnections have led to reliable, high performance solutions that can fit the tightest spaces available, even at the most difficult interconnection angles.

AVIONICS

Avionics applications have limited space as they accommodate more application needs throughout the airframe. In the past, it may have been common to have 12 antennas on an aircraft, but there are now 50—even hundreds in some cases—antennas serving advanced avionics systems. More antennas in aircraft environments leads to more signal paths and the need for more RF interconnect solutions to accommodate them.

5G

As more users rely on 5G services, more antennas will be needed to provide coverage, both at lower FR1 frequencies (under 6 GHz) and at higher FR2 mmWave frequencies. Antenna densification is required to deliver increased peak data speeds, ultra-low latency, enhanced reliability, enormous network capacity and increased availability for 5G. Many 5G networks employ MIMO antennas, which are shrinking in size as higher frequency bands are used to accommodate larger bandwidth requirements. This translates into more antennas in smaller spaces and more RF interconnections within those smaller spaces.

5G small cells, such as micro, pico and femto cells, are examples of the electronic densification within 5G networks as they are spaced much closer than traditional wireless macrocell towers, often only 100 yards apart. Demand for high density cabling solutions to accommodate the necessary
connections in smaller, more compact installations will continue to grow.

SPACE

Equipment used to support space technology must be lightweight, compact, reliable and capable of withstanding high levels of shock, vibration and radiation, as well as wide
temperature ranges. RF coaxial cable assemblies must be designed to perform reliably in the smallest possible footprint. The high frequency cables required for space applications
must support low loss communications, requiring a dense network of antennas.

HIGH DENSITY INNOVATIONS ABOUND

High density RF interconnection solutions have evolved from individual assemblies with multiple coaxial connectors to a single connection port. There are a wide variety of unique high density options suited to fit the specific needs of an industry/application, including multiport and mini-multiport connectors, bundled cable assemblies, locking miniature blind mate connectors and cable assemblies for densely packed in-the-box applications. Common requirements for these environments include ease of installation, high vibration (cannot come apart) and environmental seals.

MULTIPORT AND MINI-MULTIPORT CONNECTORS

Multiport and mini-multiport connector solutions are ideal for high density avionics environments, where space is at a premium, accessibility for maintenance is limited and performance is mission-critical. These connectors consist of multiple coaxial contacts of the same interface integrated
into a single connector module or shell. There are numerous options for these types of connectors, including those with reduced size and weight that provide excellent electromagnetic shielding and phase stability with low VSWR and insertion loss to 20 GHz for multiport connectors and to 40
GHz for mini-multiport connectors. See Figure 1 and 2 for examples.

BUNDLED CABLE SOLUTIONS

Densification creates numerous challenges related to installation, torquing, ensuring proper weather sealing and more. In addition, an increasing number of technologies such as 5G small cells have limited space for equipment, so minimizing size and weight are also key goals.

With so many components in such a small space, maintenance can be challenging. If an interconnect fails, it can be hard to troubleshoot the exact one. Moreover, installation can be a time-consuming, labor-intensive and logistical nightmare. Hooking up the right cables, ports and torquing can be difficult when working with multiple connections. Proper weather sealing is also necessary; it is imperative to ensure that the seal is secure but not over-torqued.

A bundled cable solution can help create the perfect flexible antenna jumper for applications requiring multiple runs, such as 5G. A spiral configuration of multiple flexible and ultra-flexible jumper cables can be created under a common polyurethane outer jacket to promote easy installation and
improved operation. The individual coaxial cable runs are spun together in a way that easily flexes, essentially creating a bundle, which is then run through a large jacket extruder where a ripcord is placed.

This design enables four or five individual cables to be fed into the back of an industry standard MQ4/MQ5 bundled connector, incorporating multiple RF ports and significantly reducing the number of cables that have to be hooked up. MQ4/MQ5 bundled solutions also save a lot of labor and enable
a more rugged solution. They also make the assembly more weatherproof and UV resistant.

Using the four- or five-conductor solution eliminates the need to create individual weather seals, resulting in tremendous labor savings. Furthermore, it reduces the need to worry about coupling torque, which is critical because all it takes is an error on just one weather seal to create a point of
ingress for water that could create a multitude of problems and even potentially shut the system down. With a bundled solution, the connection between the male and female cluster connectors is sealed to IP-67, as are the connector bodies and the transition from the cluster connector to the bundled cable. Any potential system troubleshooting becomes much easier. Finally, the possibility of hooking up the wrong cable to the wrong port is eliminated. The solution is keyed, so the cables can only be hooked up a certain way—no torque wrenches, know-how or special technique required.

Bundled solutions are optimal for high density challenges as they permit installation in tight spaces; instead of connecting multiple threaded connectors, just one will do the job. They are faster and easier to install and maintain and provide one firm, reliable connection to support consistent high performance. Their design has many use cases, thus becoming particularly popular in applications
where cable installations and rising operating frequencies demand coaxial cables and connectors to deliver high signal integrity and reliability. An example of this type of solution is the TMQ4 and TMQ5 bundled cable assemblies from Times Microwave Systems shown in Figure 3.

LOCKING MINIATURE BLIND MATES

A new generation of locking miniature blind mate connectors (TLMB) is specifically designed to overcome performance issues arising from typical SMP connectors’ susceptibility to electromagnetic interference (EMI) and electromagnetic compatibility (EMC) interference, liquid and salt ingress. Their rugged, sealed design is more durable to withstand harsh conditions and operate in severe environments. TLMB connectors retain the small form factor of the SMP for highly dense environments but add improved environmental, shielding and power capabilities, with a frequency
range from DC to 60 GHz.

While SMPs are still a valuable connector option for many designs, they pose problems as applications demand higher and higher frequencies. One of the critical issues is shielding and EMI.
Similarly, the SMP’s design reduces its ability to function without affecting other equipment in the same environment. The connector’s signal leakage issues often result in failed EMC tests. In short,
the SMP’s lack of proper electrical bonding and shielding exposes the conductor’s signal to external influence.
This signal leakage limits how closely the connectors can be placed in a single shell; without proper shielding, the contacts must be kept at a greater distance to prevent signal interference. With the improved shielding of a TLMB, more connectors and cables can be added in a much smaller footprint without interference issues.

Another major failure area in the SMP’s design makes them susceptible to ingress from saltwater, fuel and other contaminants. The lack of an environmental seal due to their mechanical openings makes SMPs prone to corrosion and failure. Another problem arises with using SMPs in high vibration applications, where their easy connect/ disconnect design makes them susceptible to unwanted de-mating in high vibration environments. TLMBs were created for high-reliability, high vibration environments such as military and aerospace. Areas where EMI may be an issue, such as
shipboard or aircraft, need an environmentally sealed and shielded connector.
The standard SMP may also disconnect in high vibration environments such as a carrier landing, weapons launch or any powerful weapons platform, making a locking miniature blind mate connector the ideal choice.

CABLE ASSEMBLIES FOR DENSELY PACKED IN-THE-BOX APPLICATIONS

Additionally, it may be optimal in high density applications to reduce the footprint required behind the connector to help install numerous cables into a very small space. Minimizing space between the cables and connectors is also necessary for the interconnect system to survive the high vibration and other harsh environmental conditions found in applications such as space and avionics.

New cable assemblies can be bent around tight corners and very closely behind the connector to minimize footprint, save space and simplify cable routing in tight spaces while offering low loss and optimized performance. Originally designed for space flight applications, this type of high performance assembly uses a compact, phase stable, highly flexible, micro becoming axial cable that can easily accommodate densely packed in-the-box applications. For example, Times Microwave System’s new InstaBend™ high performance microwave assemblies provide a flexible
preassembled design for interconnects between RF circuit cards, modules and enclosure panels. InstaBend is ideal for in-the-box applications with space constraints, including space flight, thermal vacuum, microwave test and other commercial and military applications. The cable can be bent very closely behind the connector, minimizing footprint, saving space and simplifying cable routing (see Figure 4). This also eliminates the need to protect the back of the connector.

Additionally, InstaBend provides these benefits at a dramatically reduced lead time compared to competing solutions. The high performance microwave assemblies are available in standard configurations or customized to meet an application’s specific needs. This new product’s ability to bend from connector to connector provides maximum flexibility and minimum use of available volume in high density, inside-the-box applications.

SUMMARY

As advanced new mission-critical technologies are introduced, RF interconnect requirements are changing drastically, including the need for novel solutions to accommodate extremely restricted space constraints and rising operating frequencies. New innovations in high density RF interconnects are emerging to deliver high signal integrity and reliability in increasingly dense environments.

When selecting the right high density RF cables and connectors, it is best to work with a partner whose engineers can identify the application’s unique needs and design an optimized, easier to use solution—creating better electrical, mechanical and environmental performance. Look for a supplier
with a long history of building quality cable and connectors, along with the skill, processes, techniques and materials to bring custom solutions for specific application needs to life

Interpretation of Electrical Test Data with Regards to Microwave Cable Assemblies

Prepared By: Dave Slack

Originally published in RF Globalnet

June 3, 2002

A cable assembly provides two essential functions in a microwave or RF system.

These devices serve to mechanically connect an RF source to its load and to serve as a propagation
medium and waveguide for the RF signal.

A cable assembly should not be considered as hookup wire. It is a passive, TEM mode, microwave
device. As such, they are system components whose performance is just as important as directional
couplers, combiners or antennas or a host of other passive microwave components.

Cable assemblies are an integral part of the microwave system and their performance is critical to
overall system performance.

To ensure that the cable assembly being considered for use in a given system will perform well
several measurements of electrical performance are commonly made.

The primary measurement parameters used when evaluating microwave cable assemblies are Voltage Standing Wave Ratio (VSWR) and Insertion Loss. These are commonly referred to in quantitative terms where specifications such as VSWR of 1.4:1 maximum and insertion loss less than 1.5 dB.

While these numerical quantities are of great importance, especially when making a pass-fail judgment, they do not tell the whole story.

When attempting to understand why a cable assembly is not meeting its quantitative requirements it
is enormously valuable to understand the qualitative features of the insertion loss and VSWR
characteristics.

A quick glance at an insertion loss and VSWR plot can yield an abundance of understanding with regards to a cable assembly’s fitness for use.

When a load is connected directly to a source most of the power delivered by the source will be transferred into the load.

In situations where the source and load cannot be co-located the load may then be separated from
the source with a cable assembly “inserted” in between them. The amount that the power delivered to the source is reduced is called the “insertion loss”. This is the loss of power due to inserting the cable between the source and the load.

There are three primary factors contributing to overall insertion loss. These are the attenuation
of the cable, attenuation of the connectors and the mismatch loss due to imperfect impedance
matching.

Attenuation of cable and connectors are functions of their respective material and geometric
properties.

Some of the factors affecting attenuation are:

• Conductivity
• Surface finish
• Dissipation factor
• Propagation Velocity
• Line Size
• Impedance
• Frequency

Figure 1 depicts a typical insertion loss vs. frequency plot of a coaxial cable assembly.

Note that the fine grain ripple on the graph becomes more pronounced as frequency
increases. This is due to the mismatch loss that is a result of less than perfect impedance
matching and will be discussed later.

Total insertion loss is the sum of connector loss, cable loss and mismatch loss.

VSWR

The theorem of maximum power transfer states that the most efficient transfer of energy will occur
when load impedance matches that of the source delivering the power.

A 50 ohms source, connected to a 50-ohm load through a 50-ohm transmission line will be the most efficient system from a transfer of energy standpoint.

In a practical system all of these impedances are not exactly matched. At the point where two unequal impedances meet a discontinuity is created. This discontinuity causes some of the power to
be reflected back from the discontinuity with the balance being transferred forward.

This discontinuity can be quantified in terms of reflection coefficient. Once the reflection coefficient of a discontinuity is quantified the Voltage Standing Wave Ration (VSWR) can be calculated. This is a measure of the reflected voltage and ultimately, of the reflected (and transmitted) power.

Figure 2 illustrates a very simple case of a perfect system containing one, very simple discontinuity. A realistic system is composed of a virtually infinite number of cascaded discontinuities.

Reflection coefficients are complex quantities containing both magnitudes and phase angles. The
composite system makes up an array whose vector sum yields the composite VSWR vs. frequency
response of the system. Figure 3 illustrates impedance vs. time of a typical cable assembly.

Figure 4 illustrates the VSWR vs. Frequency plot of the cable assembly whose impedance characteristics is illustrated in figure 3.

Return Loss is another way of understanding the relative impedance match (or effectiveness of power transfer) of a cable assembly. Return loss is the ratio of power reflected to power delivered and can be calculated as follows:

Return Loss (dB) = 20 log l Γ l

The return loss vs. frequency graph of the above assembly is shown in Figure 5.

A VSWR plot, to the uninitiated, can be a very confusing plot. One is tempted to seek the maximum
value and make a “pass / fail” decision based on this value. In reality there is a wealth of information contained within this presentation.

A cable assembly, in its simplest sense, is a relatively uniform impedance cable with two
connectors installed on both ends. Each of these connectors typically has impedances that are
slightly different than the cable and probably slightly different than either the source or load.
These connectors are separated be the signal propagation time, or electrical length of the
assembly.

A standing wave pattern created by these two connectors will be a function of the magnitude and
phase angle of the two connector reflection and the electrical length separating them.

As frequency is incremented from lowest to highest operating frequencies the phase angle of the two
reflection coefficients, in relation to each other, also varies. If the swept frequency band is
wide enough the two interacting reflection coefficients will be in phase at some frequencies and out of phase at some frequencies.

When the relative phase angle is zero degrees the two magnitudes will algebraically add and VSWR
will be at a maximum. When the relative phase angle of the two are 180 degrees out of phase the
two, equal magnitude, reflection coefficients will subtract and VSWR will be minimum. If the magnitude of the two reflection coefficients are equal they will cancel each other completely at frequencies where they are 180 degrees out of phase.

When cable assemblies are longer the propagation delay is longer. This causes the frequency
differential between the peaks and nulls to become smaller. For a short assembly the VSWR vs.
Frequency plot has a long period to it and represents a rectified sine pattern. As the assembly
becomes longer the VSWR pattern takes on a fine grain “ripple” effect.

As the cable assembly deviates from this simple model towards a more practical model the VSWR
pattern becomes more complex. The individual parts of a connector will interact with each other.
The time delay between these parts is small. This causes a fine grain VSWR to be superimposed on a long flowing pattern.

Termination Problems

When the two primary reflections (usually the connectors) are equal, or close, in reflection
coefficient magnitude the VSWR maximums will be low and the VSWR minimums will be very close to unity.

This canceling effect is usually not complete because of the attenuation of the cable. This is why
a complete canceling may occur at lower frequencies and become less complete as frequency
increases.

When the VSWR nulls significantly deviate from 1.0:1 VSWR it is indicative of a problem with one of
the connectors. It is letting us know that the reflection coefficient magnitudes of the two connectors are no longer close to being equal.

This can be caused by high resistance contact points within the connector, poor solder quality, or a high reactive impedance mismatch caused by an incorrect dielectric.

Figure 9 illustrates two separate assemblies. One having a high VSWR and the other having a normal VSWR.

The high VSWR assembly is slightly longer in length (and higher in loss) such that their respective
curves do not overlay each other. From the quality of the curves the effect of the high VSWR on
insertion loss is readily apparent.

The fine grain ripple due to mismatch loss that is superimposed on the attenuation curve is much greater on the high VSWR assembly.

“Suckouts”

For purposes of theoretical analysis transmission lines are commonly modeled using lumped constant parameters. The distributed capacitances and inductances are lumped into discrete components from which transfer functions and other mathematical tools may be derived.

The lumped constant model of a coaxial transmission line is that of a multi pole, low pass
filter as shown in Figure 10.

For a coaxial system to work properly all of the mechanical mating parts must have complete contact, throughout 360 degrees of circumference of the inner and outer conductors. When
parts are not correctly assembled, or not mated with sufficient contact pressure, this 360-degree contact is not maintained and a resonance can result.

The resultant lumped constant model is illustrated in Figure 12. A parallel LC tank, at resonance,
presents very high impedance. This causes the transmission line model to have a band stop characteristic that is not desirable in most applications.

The center frequency and bandwidth of the band stop characteristic is a function of the degree of separation severity of the mismatched parts.

The effect on insertion loss and VSWR are illustrated in Figures 13 and 14.

The effect can be further noted when viewing impedance vs. time (distance) plot of an assembly having mismated or loose parts. Fig 15. It is evident upon inspection of the plot that the input connector displays significant “ringing” that is typical of a resonant condition.

Impedance Uniformity (structural return loss)

Until now we have been considering the cable part of a cable assembly to be of uniform impedance. We have considered the connectors, and their interactions, to be the cause of the VSWR effects. In most cases the connectors are the primary contributor to VSWR and the cable is the primary contributor to insertion loss.

There are cases where, for a variety of reasons, the cable impedance uniformity is less than perfect. This is illustrated in Figure 16.

These sorts of “structural” discontinuities yield a non-uniform, non-repetitive VSWR pattern. This type of pattern is typically referred to a high structural return loss as illustrated below.

Cable Spikes

When impedance discontinuities are very repetitive and consistently spaced there will be a specific frequency where all of these repetitive discontinuities will add. At this frequency a very magnitude, narrow band VSWR characteristic can be created.

This phenomena is commonly known as a “cable spike”. The larger the discontinuities, the more
consistent the spacing, and the longer the amount of cable affected the larger the cable spike can become.

This can be an especially frustrating problem in the manufacture of cable for use at microwave
frequencies. These cables are typically quite broad band so that any tendency to have a cable spike
will most likely occur somewhere within the operating band of the cable.

Most of the operations employed in the manufacture of cable involve rotating machinery. The repetitive nature of rotating machinery is often the cause of cable spikes. Through the use of quality machinery, diligent maintenance and active quality control measures the spike problem can
be effectively eliminated.

Figure 20 illustrates the impedance plot of the cable spike assembly. Figure 21 is a close up showing the fine impedance discontinuities and their repetitive nature. A period of 90 pico seconds causes the 11.1 GHz spike noted in Figure 18.

Modeing

A coaxial cable assembly is designed to operate in a Transverse Electro – Magnetic (TEM), or coaxial mode. In a TEM wave both the electric and magnetic fields are at right angles (transverse
to) to the direction of travel.

The coaxial structure will not support various “wave guide” modes of operation as long as the half
wavelength of the signal being propagated is less than the mean circumference of the coaxial
structure.

These higher order modes allow circulating fields to exist that are in a direction not transverse
to the direction of propagation. These circulating currents absorb energy that is no longer
available to be transferred to the intended load. These currents tend to be unpredictable and
unstable and are generally not desirable.

The maximum operating frequency, that is free of TE or TM modes, is referred to as the frequency of cutoff (fc). This is illustrated below.

A VSWR and insertion loss plot of a cable assembly operating beyond its cutoff frequency is shown in Figure 19 and 20.

Figures 24 and 25 are a 3 GHz section of Figures 22 and 23. These serve to illustrate that, unlike a cable spike, the effects of operation beyond cutoff are not always evident in the VSWR plot.

Dents

One of the more common causes of failure of a cable assembly is for the cable to become crushed or dented. Cable impedance is a function of geometry and propagation velocity of the dielectric core.
This can be calculated as follows:

where Zₒ is the impedance, Vg is the velocity of propagation, D is the outer conductor diameter and d is the center conductor diameter.

When the cable is crushed or dented the outer diameter (D) is reduced and the Vg is also reduced.
This lowers the impedance and causes an impedance discontinuity.

The following series of figures illustrates the effects on impedance and VSWR when a good assembly has dents imparted into it.

Contamination Ingress

Another common failure mode is that of contamination ingress into the dielectric of the cable structure. This can be caused by compromise of the vapor seal of the cable assembly or by the use
of solvents or other aromatic materials during the manufacture of the cable assemblies.

This failure manifests itself in the form of lower impedance where, the core is contaminated, as
well as an increase in insertion loss by more than the increased mismatch loss would normally indicate.

If the contamination ingress is due to solvents used in the installation of the connector the impedance discontinuity will be evident at the beginning of the cable assembly as shown in Figure
34.

The contamination may also enter the cable through a puncture or tear in the vapor barrier of the
cable. In this case the impedance discontinuity would appear in proximity to the leak.

Conclusion

With a discerning eye towards the qualitative presentation of cable assembly test data, the
discriminating consumer of these products can easily, and quickly, identify the most likely cause
of cable assembly problems.

Once the most likely cause is identified the real work of implementing root cause problem solving techniques and practices can begin.

Summary

This presentation will tackle the nuances of high-power applications involving coaxial cable assemblies. Different types of power and their impact on cable integrity will be discussed along with case studies that show how coaxial design can make the difference between safe operation or potentially dangerous operating conditions.

Watch the video or read the session notes below.

Session Notes

How Different Types of Power Affect Coaxial Cable Performance

When it comes to high power issues related to coaxial cable assemblies, it’s important to understand how power is classified and how it is used in real-world settings:

• High current: Found in industrial applications like semiconductors
• High voltage: Found in energy storage of high power, fractional duty cycle applications
• High power: Found in aerospace applications such as electronic warfare

High Current

Generally, current carrying capability is directly proportional to the crossed area of conductors. Therefore, the larger the conductor, the lower the resistance, the higher the current carrying capability. This drives the need for large cables and connectors.

Similar to a water pipe, more current can efficiently be produced through a larger conductor, which can be accomplished by simplifying the conductor design. A conductor with fewer piece parts and contact points provides a more robust design.

High current can also lead to sources of localized hotspots and weak spots in the design, and there are specific techniques and design features that can mitigate that issue.

High Voltage

High voltage power has arcs and flash-overs, essentially miniature versions of lightning bolts. Like lightning bolts—where huge amounts of charge are built up between the clouds and the surface of the Earth—voltage can increase between a generator and the ground to the point that it can no longer withstand the voltage and is released.

In this application, it is not so much about the size of the conductors but the capability to isolate and insulate one conductor from the other, or the cloud from the ground. This can be achieved by putting a high dielectric strength insulator between the conductors.

High Power

High power is thermal-related, continuous wave (CW) energy. The issue here isn’t voltage or current; it is the heat that is generated. When power is pumped into a cable assembly, some loss or inefficiencies occur. That lost power must be dissipated.

The issues are generally thermal and heat buildup, and the cable’s ability to transfer heat from its internal environment to the external environment. One mitigation technique is to increase the surface area of the component to radiate heat.

Conclusion

When failure modes happen, they can be dramatically catastrophic. Therefore, it is important to choose the right components, ensure that those components are designed to mate together, and that the cable and connector interface are designed to work together.

It is critical to use a connector that’s designed specifically for a cable and for a specific power application. They should also be installed and assembled by people who are experienced and understand the issues.

Q&A

Following are the questions that were asked by the audience:

• What is the most important component when selecting an assembly for high power?
• Does electrical performance change as cables get hot? What can we do to control or mitigate that?

To learn the answers and hear the full detail provided in the webinar, register now!

Summary

Searching and qualifying an RF interconnect supplier for space applications can be a lengthy and costly process. Some suppliers offer standard qualifications and documentation for basic products in hopes of simplifying this process. But nothing is standard, or easy, in space. In this session, Maria explains the 5 steps for evaluating an RF partner’s capability to handle the custom designs, special testing and qualifications required in space.

Watch the video or read the session notes below.

Session Notes

Designing a crucial interconnect system that will perform well and withstand the extraordinary environmental and technical conditions of space, reliably and consistently over long periods of time, is not like designing just any RF interconnect system. The conditions encountered in space are unique and require special, highly customized solutions to prevent failure.

Custom designs, special testing and qualifications, and new product development for space applications require experience and commitment. “Standard” RF systems are not good enough in space. It’s important to thoroughly evaluate the capabilities of an RF supplier to ensure a positive outcome.

5 Steps to Find the Best RF interconnect Supplier

To ensure the best possible performance for these special applications, as expediently and cost-effectively as possible, consider your RF partner’s:

1. Qualifications and heritage
   Many suppliers offer a good list of standard qualifications, but in space, your requirements may be unique. Look for partners that have experience in space, and in other areas such as military and defense.
2. Dedicated technical experts
   Always ask to speak with technical experts. The complexity of space applications requires an effective partnership; choose a supplier that will work collaboratively as an extension of your design team. You’re not looking for a standard solution, so it’s important that your RF supplier’s technical team asks questions and listens to understand your unique needs. Don’t work with a supplier that’s committed to selling you the same product they’re selling everyone else. Your supplier should help you understand the electrical and mechanical trade-offs particular to your application, as well.
3. Breadth of products
   A provider that offers a broad range of products is simply better equipped to sell you the right system for your application. You want to be able to select the right material, choose from multiple cable constructions, various connector designs (low power, high power, etc.) and assembly techniques, all from the same supplier. Plenty of technical standards must be met for products to be deployed in space, such as using only acceptable materials or mil-spec cable constructions. There is, however, no standard for how to apply these materials to construct an RF solution that is reliable time after time. That is where your supplier’s expertise and access to a full range of product options are needed.
4. Manufacturing execution
   Ideally your supplier has all the technology and products you need and understands how to put them together into a final product. The next qualification to consider is the supplier’s manufacturing operations. Does the company have robust facilities and processes to support execution? Cleanroom manufacturing capabilities are key. Traceability is also important for managing all the piece parts that make the complicated assemblies. What quality standards does the supplier follow? What about extended services?
5. Agility
   Be sure to choose an RF partner that is strong enough, financially and operationally, to deliver and survive through turbulent times. The last year has proven just how important it is to always remain agile and adaptable, in business and in life. Bad things sometimes happen. Can your supplier adjust quickly? The right partner will flex with you to deliver the value you need, every time.

All five selection criteria are tied to crucial performance capabilities, so consider their importance when evaluating potential RF suppliers. Choose wisely and enjoy a successful outcome that lasts.

To hear the full detail provided in the webinar, register now!

Summary

In this session, Dave provides an overview of Times Microwave’s expertise in designing coaxial cable solutions for a wide range of applications. Starting with the company’s deep experience in supporting electronic warfare systems, Dave explores how the company has adapted to enhance its capabilities to meet the changing needs of industries that demand more power and precision from cabling and measurement solutions. The webinar also examines how the Times Microwave approach is helping to solve challenges that would be nearly impossible to address without a flexible, scalable coaxial cable application ready for deployment.

Watch the video or read the session notes below.

Session Notes

There are five common RF use cases that require coaxial cables and connectors, and each type has its individual characteristics and challenges.

Communication

A traditional place for coaxial cables has been in wireless communications, including mobile/telecom, two-way radio, public mobile radio/land mobile radio, satellite communications and military communications. The challenge with these types of voice-based applications is the signal to noise ratio. This is critical as any degradation of the signal will cause information to be lost.

Therefore, factors that must be considered in determining the optimal coaxial cables and connectors include low loss, shielding so that signals from outside can’t interfere, and reliability with 99.999% up time. This has been a traditional application for Times Microwave LMR® cables. The product line up has evolved to include additional options to meet the needs of 5G and Low-PIM such as SPP™, TFT, small cell cables and more. We also have TCOM cables for deploying emergency cell sites.

Vision

In this case, RF is used as a way of viewing the world, most often in places where the eyes cannot see. The classic example is radar. Essentially, vision applications use RF signals to locate and identify potential threats, landscape features, and more. This type of system is typically found in military airframe electronic warfare systems, ground radar, anti-missile defense, guidance systems, aviation collision avoidance and similar applications.

Times Microwave has a long legacy creating optimized solutions for military airframe electronic warfare systems and many other related technologies. The common challenge is the multiple antennas and location sensors that all come back to a common point. Vision systems work by looking at the differences.

So, what’s the challenge when it comes to the cabling? One, these systems are in difficult places— extreme and highly variable conditions in terms of elevation, temperature, and more—and the signals need to travel at consistent speed independent of these elements.

This is critical as unaccounted-for variations could mean a system is “looking” in the wrong place. Additionally, if any phase or amplitude errors are being introduced into the multi-antenna system, it will cause a problem. Therefore, amplitude and phase stability across temperature and between cables is a key challenge in finding the right coaxial cable and connector solution for vision applications.

Data Systems

Sensors and other data systems are a big investment area now. These are systems that are essentially designed to get feedback needed to understand what is going on in a particular environment.  An example is measuring the water content in soil to optimize field irrigation.

What is the challenge with sensors? They are typically used in extreme environments or locations that are difficult to access. For example, it is very difficult to do soil samples every morning on a 100-acre cornfield, so sensors are used. They are also useful in contaminated areas, or nuclear applications where it is not safe. This means that once the cable is installed, it might not be easily accessible for replacement.

Additionally, even though the process typically involves a quick measurement from a sensor connected to an antenna, reliability is key. If a critical system dependent on a sensor does not work, things can quickly go haywire.

Data systems require coaxial cable solutions that can withstand the rigors of these important applications. Times Microwave engineers are skilled in looking at this intriguing world and figuring out how to architect the best interconnect solutions to meet its challenges.

Test and Measurement

Test and measurement applications are used to test RF equipment during the design and production stages. An example of this is a program testing electronic warfare systems before they go into F-35 aircraft to ensure they can identify potential threats with the utmost reliability.

This environment requires unique coaxial cables and connector solutions— repeatability, reliability, and reproducibility are critical to make sure the cable itself is not introducing uncertainty to the test. This includes ensuring amplitude (low loss) and phase stability. Flexure is also key as these systems (and cables) are connected and disconnected often and are used repeatedly, so the connectors must be able to withstand extensive handling.

This use case also fits nicely with Times’ unique capabilities and products. Test and measurement requirements often demand a special type of cable—for example, one that needs to be flexed or bundled with another type of cable into a multi-pin type of connector—and Times will tailor a custom solution for the application.

High Power

These applications vary a bit from those previously mentioned because RF is used to transmit power in this case (such as activating a magnet or gas) rather than a signal. RF is used in these instances because cables are easier to install than pipes or other options. Examples include lasers, deposition equipment, physics test equipment, microwave ablation, industrial microwave ovens and MRI machines.

Therefore, key system parameters include flexibility and low loss. Power also generates heat, so the cable jacket temperature needs to be optimized for a particular power level. Materials and constructions are important to prevent overheating and to ensure ease of installation.

What Makes Times Microwave Unique?

Coaxial cable technology is being used in places you’ve likely never thought of before. Times Microwave applies its deep knowledge of this technology and dedicated engineers to create coaxial cable solutions for many different applications—whether the application is communications, vision, data systems, test and measurement, high power, or anything else. Bring us your tough challenges and I promise with almost 99.999% certainty that Times Microwave will be able to come up with a solution that meets your needs.

Summary

In this session, John explains how Times Microwave Systems’ test cables are used in test and measurement applications, and how the company’s core products are suited for various uses. He also explains how higher frequency ranges and the rise of 5G are driving development of more advanced cabling products, with more robust features and higher levels of customization now possible. Finally, the session drills deeper into popular products like Clarity™, Silverline®, Silverline®-Extra Flex, and Silverline®-VNA and how they are being used in the testing world today.

Watch the video or read the session notes below.

Session Notes

Test leads are used in essentially every manufacturing space related to electronics, avionics, test equipment, semiconductors, and more.

RF testing requires unique coaxial cable and connector solutions. The cable assemblies must be durable enough to withstand extensive handling and continuous movement from frequent connecting and disconnecting, while maintaining precise repeatability of measurement and reliable electrical performance. It is critical that the cable, cable assembly and connector do not introduce any problems.

New technologies such as 5G have introduced more testing challenges. The increased speed of 5G is achieved in part by using higher-frequency radio waves. Unlike previous cellular technology generations that were focused on a specific frequency band, 5G operates across a much larger frequency range. For example, 5G can range from 450 MHz to 3.9 GHz, and up to 20-52.6 GHz millimeter-wave bands for high-speed operations. It also encompasses unlicensed frequency bands, such as the 6 GHz band.

Rapidly advancing technologies are also increasing the complexity of test setups, requiring more test leads and connection points than ever before. This makes it necessary to revisit how connection points and test leads are built as well as the different types of connectors available—while ensuring that the latest test assemblies work in concert with the changes made by test equipment manufacturers.

Another key aspect is related to the need to constantly move the cables around. Movement introduces phase change, which can impact measurement accuracy. Robust cabling is therefore critical to keep phase as stable as possible.

Additionally, when testing technologies such as 5G, the source and receiver might be running at two different frequencies at once. A phase-stable assembly will help ensure that harmonics are not introduced back into the system.

Times Microwave SilverLine^® and Clarity™ Solutions

SilverLine test cables are cost-effective, durable, high-performance cable assemblies designed for use in a broad range of test and interconnect applications. The PTFE dielectric cable features stainless steel connectors and a molded strain relief system, providing long life and excellent phase stability in applications where the cables are repeatedly flexed and mated/unmated. Because Silverline tolerates a very wide temperature range – up to 125 degrees Celsius, it can also be used outside of a test bench.

SilverLine-ExtraFlex was designed for testing delicate components such as exposed RF circuits with edge launch connectors. It uses Times’ proprietary TF-4 dielectric, exhibiting a very linear phase change from 0ºC to +30ºC. It also uses the injection-molded strain relief system for extremely good isolation, and the same robust, proven connector attachment system as SilverLine.

Silverline-VNA cables are designed for the highest frequencies presently available, 70 GHz through 110 GHz. Their construction method is different than the others, as there is no unarmored option, to keep phase stability in check.

Times Microwave’s Clarity line includes highly stable RF cables with flex in a very robust package for accurate measurement. It features excellent phase stability, extremely low loss, an ergonomic molded boot and a large connector selection. Utilizing the flexible TF4 dielectric allows for accurate S parameter measurements and even when movement occurs in the production environment, the proven solutions cover a wide frequency range from 18 GHz to 50 GHz.

It is also important to use a very flexible cable material that can be moved around on a test bench, either in R&D or in a production environment. Testing often moves from module to module. With high frequencies, this could require recalibration every time a module or cable is moved. However, using a cable that can bend and flex will greatly reduce the amount of recalibration required while maintaining stability. Where Clarity really shines is its ability to connect and disconnect without having to do different calibrations in between.

Q&A

Following are some of the questions that were asked by the audience:

• What is the mating cycle for your test leads?
• What is the difference between an LMR and a test cable?
• What are the common failing mechanisms for test leads and where do they fail?

To learn the answers and hear the full detail provided in the webinar, register now!

Summary

The webinar is the second in a two-part series on phase stable cable assemblies and electrical length changes within cable assemblies in aerospace engineering and space technology development applications, among others. In this session, Dave Slack digs deeper into the impact of temperature on phase behavior. He explains the polytetrafluoroethylene (PTFE, also known Teflon™) “knee” that exists in some cables and how it impacts their phase performance. Slack also provides guidance on minimizing those effects with special materials, such as cables made from silicon dioxide (SiO2) and TF4.

Watch the video or read the session notes below.

Session Notes

A typical phase versus temperature signature of a flight-grade cable, circa 1995, would have been a 76% velocity cable made with a PTFE core. These cables were very rugged and resistant to damage during installation and maintenance.

Typically, there would be a relatively flat phase/temperature slope below room temperature. However, at room temperature, there is an abrupt jump that changes the phase temperature profile. This is due to a peculiarity of Teflon—a nearly perfect dielectric material for cable, RF and microwave applications because it has a constant dissipation factor as well as a constant loss tangent across a wide range of frequencies and temperatures. However, Teflon undergoes a mechanical or materials phase transition in which it changes density by about a percent and a half between 18-22 degrees Celsius, or 64-72 degrees Fahrenheit.

That change in density also causes a change in dielectric constant, which, as discussed in the Phase Stable Assemblies 101 webinar, creates a  velocity change.  This in turn produces an abrupt change in electrical length—a very common phenomenon known as the Teflon knee, or the PTFE knee.

A cable assembly gets electrically longer as it gets colder, and shorter as it gets warmer – contrary to what one might expect. Electrical length is proportional to physical length. Metals expand as they get warmer and contract as they get colder but as that happens, the dielectric constant expands and contracts as well and its density changes, altering the velocity. The dielectric effects of the plastic offset and dominate the metal effects.

Phase-matched cables are in pairs or groupings. As temperature changes to cold or warm extremes, they don’t exactly track together; the phase match degrades just slightly. That small amount of degradation is known as its phase tracking characteristic.

In a practical situation, a cable assembly might be phase matched to the initial assembly with a tolerance plus or minus a degree. The slope is the same, but it is offset by that initial match. The uncertainties and errors that accumulate with changes in temperature are the initial phase match plus the phase tracking; the two add to each other.

In another scenario, there may be two cable type families – a full-density and low-density PTFE. The vertical scaling is very large, in an 8,000 part-per-million window. Full-density solid Teflon actually takes up every bit of that scale. It has a relatively extreme slope below and above the knee, and a very pronounced step function during the phase transition temperature.

In the following example, we compare this against the low-density PTFE, with 10 cable assemblies of each family superimposed on top of each other, all phase matched at room temperature, tested and plotted across temperature. As it changes to extreme heat or cold, the cables are no longer perfectly phase matched; they differ from each other.

We tested two cable assemblies to look at phase versus frequency. One cable is a PhaseTrack® cable, and the other is a standard PTFE cable. When a freeze spray cools the cables down, the PhaseTrack cable stays consistent, whereas the PTFE changes because of the phase temperature knee. That causes antenna beam forming characteristics to defocus.

Because of these complexities, there is value in dealing with a supplier that offers a range of different technologies, and can provide optimized solutions for each unique application.

To hear the full detail provided in the webinar, register now!

Summary

The webinar is the first in a two-part series on phase stable assemblies and electrical length changes within cable assemblies. In this session, Dave Slack shares his insights on the importance of phase in cable assemblies. He explains what it is, why it matters, and how it can be properly specified for precise performance requirements in aerospace engineering, space technology, and more.

Watch the video or read the session notes below.

Session Notes

What is Phase?

Phase is a key parameter for detection and measurement in many RF/microwave systems including radar, direction-finding (DF) systems, and missile defense systems. Phase must be accurately controlled in the components within those systems, such as coaxial cables and connectors.

The concept of phase starts with the fact that a microwave signal propagates in the form of a sine wave. For every cycle of a sine wave, 360 degrees of electrical length is accumulated. If 50 cycles per second accumulate, it is a low frequency, with few cycles per unit of time, and a relatively long wavelength. At a higher frequency, millions or billions of cycles per second will accumulate, and the wavelengths are exponentially shorter.

Frequency, time delay, and physical properties including dielectric constant and propagation velocity all affect electrical length. Environmental factors are also very important, such as temperature fluctuations, flexure, handling, twisting, pulling, crushing and more.

Why Do Phase-Stable Assemblies Matter?

Phase-stable cable assemblies are important in today’s increasingly sophisticated electronic systems. In aerospace engineering and space technology applications, phased array antennas, synthetic aperture radars, and direction finding are all phase-sensitive uses. For example, electronically steered antennas use a variety of radiating elements, and then vary their phase relationships to control the radiation pattern, so they can switch from a search radiation pattern to a tracking radiation pattern or shift direction very quickly. All these elements are fed by transmission lines; beam accuracy depends upon the phase relationships between those cables. Phase is also responsible for precision in some of the more time-sensitive satellite applications like GPS systems, mobile cellular, military radar and more.

Specifying Phase-Stable Assemblies

There are two ways to spec a phase-stable cable assembly. One is to specify it in terms of an absolute quantity or to talk about it in relative terms. For the absolute electrical spec, you would determine that the cable assembly is 5,271 degrees +/- 1, for example. You can buy a cable and specify that as an absolute length in terms of time delay, 5.1 nanoseconds +/- 0.1, etc. It’s very convenient and easy. Then there’s the relative way of specifying cables, which is one cable assembly relative to another. Whether it’s 10,000 degrees or 20,000 degrees all that matters is the cables are the same electrical length within a specific tolerance.

As frequencies get higher and higher beyond the UHF frequency range, a million degrees can accumulate easily, making the absolute electrical length measurement a challenge. At high frequencies, tight tolerances and really short wavelengths, a relative measurement can be much more precise using a relative measurement.

Sometimes specs are requested that we think are impossible, but at Times, we roll up our sleeves and gather around the whiteboard to figure it out. What was impossible just a few years ago is typical today. And that’s going to continue: what is impossible today will be typical tomorrow.

To hear the full detail provided in the webinar, register now!

Summary

Technological advances across industries are leading to more complicated requirements for RF systems to accommodate higher frequencies, inside of devices that are continually getting smaller. Cabling for these systems is a challenge because in tight space configurations, traditional semi-rigid solutions have shortcomings. Using flexible cables that are specially designed to optimize space, bend around tight corners, and connect to various ports without wasted cable length is emerging as a preferred option. Durability and material selection are additional considerations as these cables are often used in challenging environments and applications like 5G, space and quantum computers.

This webinar details new and emerging solutions for RF interconnect systems that are easy to install, low maintenance, and cost-effective, enabling the latest, most advanced in-the-box applications. Watch the video or read the session notes below.

Session Notes

The higher frequencies demanded by today’s advanced RF and microwave communications—up to 110 GHz and beyond in some cases—require smaller equipment installations, densely packed with ever more technology. That means smaller cables that must fit into extremely tight spaces, with more interconnect requirements. Cabling from the front panel to the board becomes more complicated, leading to more difficult packaging challenges.

At the same time, RF systems are being used in many new places where they were never required before. As a result, environmental challenges are also becoming greater. It is a fairly complicated design problem: make the boxes smaller, put more into them, and ensure they survive in the most challenging places imaginable.

On top of that, 5G is also a rapidly growing technology; the small acronym covers a huge array of applications. One of them is the Internet of Things, which has made it economically viable to put radios on just about anything.

Moving Beyond Semi-Rigid: InstaBend™

Semi-rigid cables would traditionally be used for many of these applications; but in very small sizes, they become too fragile, making installation difficult as these types of assemblies are more prone to breakage. Semi-rigid is also more complex and time-consuming to manufacture because the cables must be bent to their final configuration at the factory.

One of the solutions that Times Microwave has developed to address this is InstaBend™.  This product family is designed and assembled for extreme flexibility to fit into small spaces for interconnects between RF circuit cards, modules and enclosure panels. You want as much flexibility as possible when attempting to route cables tightly. InstaBend cable can be bent very closely behind the connector, saving space and simplifying cable routing.

The product family includes assemblies offered in two sizes: the InstaBend 047 and InstaBend 086. They are available in various lengths to make connections with minimum footprint. Connector types include SMP, SMA and 2.92 mm.

InstaBend is available within short lead times: standard configurations are stocked by many distributors, including DigiKey and Mouser, and custom configurations are available from Times Microwave with lead times of two to four weeks for the complete assembly.

TLMP Connectors

Times Microwave has also developed its TLMP (Times Locking Miniature Push-On), a unique miniature connector to address the common challenges with vibration and shielding compared to a traditional SMP.

TLMP connectors offer striking improvements over SMP connectors, and although they are miniature, they are rugged and durable to withstand harsh conditions. With highly dense connectors, making sure the interconnect is fully engaged is a challenge. TLMP connectors feature a locking mechanism that prevents possible de-mating during mechanical or vibration shock. Color indicators signify “positive locking” to quickly confirm proper installation—the coupling interface reveals a red band when unlocked and shows green when properly mated. This feature maintains the connector’s mate integrity even during extreme shock and vibration and prevents materials like fluids and gases from entering the interface.

When Semi-Rigid is Required

A flexible cable may not always work in extreme environments, so Times has also developed a new silicon dioxide semi-rigid cable that can withstand an incredibly broad range of temperatures from just above absolute zero up to 600^oC and beyond. It is a very good low-loss cable, and it processes like a semi-rigid, but it can withstand temperatures, radiation, or just about any challenge.

Conclusion

Times Microwave designs robust and cutting-edge interconnect solutions to meet both electrical and environmental challenges outside and inside the box—and anywhere else you can imagine.

Q&A

Following are the questions that were asked by the audience:

• What is the lead time on the IB-047 and IB-086?
• What are the cables on the quantum computer image? Does Times Microwave make those?

To learn the answers and hear the full details provided in the webinar, register now!

Summary

RF technology is an increasingly important part of many new healthcare technologies that are making the hospitals of the future possible. For example, today’s healthcare providers are increasingly utilizing advanced medical diagnostic, imaging, and treatment systems, including computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound systems, to enable earlier detection of potential health conditions.

One element these systems have in common is that RF technology is used to power many of their critical functions. Medical electronics applications depend on high performance and reliability from components such as coaxial cables and connectors.

Watch the video or read the session notes below.

Session Notes

Medical advancements that depend on RF performance can be narrowed down into three main categories. These include electrosurgical devices such as lasers, robotic surgery, radiofrequency ablation (RFA), microwave ablation (MWA), and even cosmetic procedures. Secondly, MRI machines leverage RF pulses carried by coaxial cables, and other diagnostic imaging technologies. Infrastructure and connectivity are the third area focused on in this webinar; it includes critical communications aspects of hospital networks and an overlapping function with patient and equipment monitoring.

As healthcare innovations continue to advance, the underlying technology needed to support them must progress too. Medical electronics applications depend on high performance and reliability from components such as coaxial cables and connectors.

Ablation and Robotic Surgery

Electrosurgery uses radio frequency, specifically high frequency alternating current, to achieve thermal effects within biological tissue. An electrosurgical device unit (ESU) consists of a generator and a handpiece with one or more electrodes. Electrosurgical generators produce a variety of electrical waveforms. As these waveforms change, so do the corresponding tissue effects.

Two minimally invasive procedures that rely on RF technology are leading the way in electrosurgical treatments.

Radiofrequency ablation (RFA) and microwave ablation (MWA) use electrical and microwave energy to heat precision areas and destroy abnormal cells. The configuration of these life-saving machines requires coaxial cables in two critical places: within the generator itself and outside of it, connecting the external probes and catheters to the generator.

These require low-loss cables that are easy to install in tight and compact places. Furthermore, using a cable with a kink-free design is ideal for installations with numerous flexing twists and turns. Connecting the probes and catheters to the generator requires cables that are small, flexible, and nimble enough for the precise movements needed when performing procedures.

A sample application in this arena is the use of Times Microwave T-COM®-400 and StripFlex® SFT- 304 solutions to hook up the generators and their inner workings. These cables are easy to install in tight and compact places and their kink-free design makes them an ideal choice for installations with lots of flexing twists and turns.

The TFT family of cables were used in another application to connect electrosurgical probes and catheters to the generator. TFT cables are small, flexible and nime precise movements that doctors need.ble enough to accommodate th

Additionally, robotic-assisted treatments are now often performed along with RFA and MWA. Improvements in technologies such as virtual reality will bring more remote procedures as well. Cutting-edge custom coaxial cable solutions are often needed to power this, incorporating features such as low loss, high performance, precision, shielding, and flexibility.

MRI and Diagnostic Imaging

Times Microwave has a long history of supplying high-performance RF interconnect solutions to MRI manufacturers. MRI works on RF pulses carried by coaxial cables like Times’ high-power LMR® 900 and HP-1200 cables.

An MRI system must be well shielded to minimize interference with a healthcare facility’s communications networks and electronic systems. The MRI patient chamber is usually connected to signal and power sources in a separate, shielded room, interconnected by lengths of coaxial cable and connectors. These cables must send consistent signals between magnetized and ordinary environments with high-power demands. This can create challenging performance requirements for the coaxial interconnections.

While conventional corrugated cables meet low-loss specifications, they are difficult to install in the restricted spaces often found in MRI applications. Cable assemblies must therefore handle suitable signal power levels without distortion and with performance levels equipping them for extreme conditions (similar to the requirements of military electronics systems). These cables need to exhibit low loss and other electrical characteristics to support MRI system performance, along with mechanical properties that can simplify installation of the system and the cables within, such as incorporating a tight bend radius for fitting into small spaces.

Regarding other diagnostic imaging applications, there are two primary types of ultrasounds that also depend on high-performance RF interconnects: diagnostic, which most of us are familiar with, and therapeutic, a high-intensity focused ultrasound for therapy and medical procedures referred to as microwave diathermy.

Infrastructure and Connectivity

RFID is used in patient tracking and inventory management applications within a healthcare setting, as well as additional uses. An RFID tag consists of a tiny radio transponder, a radio receiver and a transmitter; it uses electromagnetic fields to automatically identify and track tags attached to objects.

Additionally, as the Internet of Things continues to grow, we will see many new and smaller wearable devices that will force RF cable diameters to get smaller and smaller. At the same time, the amount of data on networks will increase, and the addition of telehealth and internal health networks and hospitals will add to this demand.

5G

As the healthcare industry continues leveraging technical advancements, the communications technology powering them must also sufficiently advance to provide adequate bandwidth to support many simultaneous users, real-time video, large data transfers, and more.

5G wireless networks are now being rolled out to provide this much-needed bandwidth, at higher millimeter-wave frequency bands. For example, telemedicine requires a network that can support real-time high-quality video, which has traditionally required wired networks. With 5G however, healthcare systems can enable mobile networks to handle telemedicine visits, which has the potential to greatly increase their reach. 5G technology can also enable patients to get treatment sooner and have access to a wider variety of specialists. The technology can also increase remote monitoring offerings for healthcare systems since providers can be confident they will receive the data needed, in real time, to help provide excellent patient care.

5G will also enable the continued development of surgical robots and the networks supporting them. Many key healthcare functions are beginning to use artificial intelligence (AI) to determine potential diagnosis and decide on the best treatment plan for a specific patient. Additionally, AI can help predict which patients are more likely to have postoperative complications, allowing healthcare systems to provide early interventions when necessary.

Ultimately, by enabling these technologies through advanced communications networks, healthcare systems can improve the quality of care and patient experience, reduce costs, and more. But 5G demands a high level of interconnectivity – the frequencies can span from 24 GHz to 100 GHz, which is much higher than traditional wireless networks.  As a result, RF performance and reliability are critical to support 5G.

Optimal coaxial cables for this environment require higher frequency, broad bandwidth, proven reliability, and low latency. Cable construction should also focus on high flexibility, low insertion loss and superior shielding.    Times Microwave solutions for higher frequencies include LMR, MAXGAIN® and T-COM products.

Q&A

Following are some the questions that were asked by the audience:

• Is there an example of a medical application Times created that you could share?
• What are the cables on the quantum computer image? Does Times make those?
• What is the smallest cable that Times is currently making?

To learn the answers and hear the full detail provided in the webinar, register now!

Summary

This webinar details Times’ FITS connector system and its use in Naval shipboard applications. The FITS connector system is designed to introduce new levels of flexibility and durability in the most grueling environments. Tony Fedor explains how the system meets the latest military requirements to withstand any number of changing conditions. In addition, he covers the improved shielding capabilities and the overall versatility of the FITS connector system.

Watch the video or read the session notes below.

Session Notes

This webinar provides an overview of the Field Installable Termination Systems (FITS™) connector system in Navy shipboard applications. Many of these systems are connected using MIL-DTL-17 coaxial cables, the base specification for military approved coaxial cables. MIL-DTL-17 sets forth the parameters for cable materials, whether they are low- or high-temperature, fluoropolymers, braided materials, etc. It also includes requirements for testing parameters, including mechanical, physical, and environmental testing.

Cables and assemblies that are qualified to MIL-DTL-17 specifications are listed in the Qualified Products Database (QPD) by the Defense Logistics Agency (DLA). There are about 250 “slant sheets” currently in the MIL-DTL-17 (commonly referred to as M17) spec, and they are all completely different with their own set of electrical, physical, and mechanical parameters that set forth the design. Times Microwave Systems currently maintains more than 160 QPL listings, including high-temperature, low-temperature, armored versions, and many more.

Buyers should use caution when ordering products to meet the M17 spec: some manufacturers use vague terminology such as “M17-type,” “in accordance with M17,” “similar to,” or “equivalent to,” etc., that could lead to false representation. Those designators are not accepted under the current QPL status. For example, a product that states it is “similar to an M17” may fail fluid testing or might not quite meet the electrical characteristics for a broadband test. These issues could have a degradative affect in the performance of any RF system, especially within a military system.

Evolving MIL17 Standards

Back in 1993, there was a MIL standard 454 directive that moved to eliminate the use of PVC on ships. Earlier specs such as MIL-T 24 640, and 24 643 were multiconductor power and control specs that moved to low-smoke zero-halogen parameters. Revision G added requirements for shipboard cables, and a Type 14 crosslink polyolefin jacketing material. This introduced a new series of testing requirements for weathering, abrasion resistance, fluid immersions, heat distortions and a variety of other physical and mechanical properties.

Slant 180 through 200 incorporated direct replacements to RG cables. For instance, an M17 slant 75 is an RG 214 PVC jacketed cable that transitioned into M17-slant 190, a low-smoke zero-halogen version with the Type 14 jacketing, as well as additional features.

Slant 210 through 218 included “unswept” versions that test one discrete frequency many times at 400 MHz. This provides no guarantee of broadband performance, and many are starting to be inactivated for their swept counterparts.

That leads us to the latest specs, slant 220 through slant 229. Times Microwave LLSB®—a series of low loss, highly-shielded designs that provide better overall performance for attenuation and shielding compared to an M17 standard RG cable—fit into this. These are the latest, lowest-loss designs that have been added to the MIL-DTL 17 specification.

In addition to electrical performance, LLSB cables carry the same combustion requirements and testing of the type 14 jacket. So M17 RG and MIL17 slant 220 through 229 cables all meet combustion requirements including flame performance, acid gas, halogen content, smoke and toxicity levels.

The Perfect Mate: FITS Connectors

LLSB cables are fully QPL’d under the M17-DTL or MIL-DTL-220 through 229. To add to this, Times Microwave created FITSä, a Field Installable Termination System incorporating a series of connectors and tools to fit LLSB cables.

The big advantage of FITS is the excellent and consistent RF performance of the connectors. They are truly field-installable with ruggedized performance and a superior plating thickness. We have created DLA part numbers for 16 approved FITS connectors, with new ones coming.

FITS connectors use a bi-metal tin nickel plating. Traditionally, tri-metal plating (zinc, tin, and copper) was used and by comparison, the bi-metal plating performs extremely well in terms of corrosion, including excellent performance with the MIL-STD-810 requirement, or the salt fog test.

Summary

Beyond Teflon®: RF Assemblies for Extreme Environments, is part of our Times Talks webinar series.

Teflon® coaxial cables offer excellent performance, but every material has its limits. Learn how to specify the best, hermetically sealed, custom-designed cable assemblies that fit your system. Our team has helped hundreds of customers specify and qualify the correct SiO2 cable assembly for their applications.

Watch this webinar on-demand or read the session notes below.

Session Notes

Teflon is a phenomenal dielectric for microwave cables. It’s lightweight, low loss, and very flexible. However, even an excellent product has limits. Extreme environmental conditions are one for Teflon. For example, applications such as hypersonic missile guidance will reach temperatures ranging from 200-250°C, or even as high as 600-1,000°C. Teflon will simply melt in those conditions.

Second would be any application that requires strict phase stability. As discussed in our recent webinars on phase performance, the ability to match multiple microwave cables to each other so the signal takes the exact same amount of time to travel through, as well as controlling how that phase relationship changes over temperature, are absolutely essential properties in microwave cables used in applications like phased array radar.

A third extreme environment is high radiation, found in applications such as particle accelerators, where two beams smashing together generate a significant amount of radioactivity.

To address the challenges, Times Microwave has developed a proprietary silicon dioxide dielectric (SiO2) that excels in these environments. Silicon dioxide is used throughout the micro-electronics industry for its excellent insulating properties. The construction of the silicon dioxide coaxial cable starts with a solid oxygen-free copper center conductor, a silicon dioxide insulating dielectric, and stainless-steel jacket that has copper cladding to act as the outer conductor.

Silicon dioxide provides excellent phase stability and low hysteresis and can perform at extreme temperatures ranging from just above absolute zero to 1,000°C. The metal and silicon dioxide dielectric construction makes the cable resist radiation naturally, up to 100 mega rads. The stainless-steel jacket is welded to the connectors with laser beam technology to create a hermetic seal.

When specifying electrical performance for these cables, the first thing to think about is attenuation or insertion loss, which will depend on the cable size selected. Next, in terms of electrical length, it should be determined if the cables in the system need to be phase matched.

There are several ways Times Microwave can phase match cables, including relative or absolute value. A third option is to establish a golden standard—Times Microwave builds and tests one of the assemblies, and the data for all future assemblies is matched to the golden standard to ensure everything produced is the same.

In terms of power handling capacity, silicon dioxide is excellent in high power applications due to the nature of its construction. However, there are a few things that will decrease the power handling capacity of the cable. The first is VSWR; the higher the VSWR, the lower the power handling capacity. Second is altitude. If the application is operating in a vacuum, it will lose the natural convection that takes heat away from the cable, which will in turn reduce the maximum power that can flow through the cable. Finally, the operating frequency will determine what the power handling capacity of the cable can be.

Case Study: Climate Monitoring Satellite

Following is an example of a climate monitoring satellite application that required a set of electrical performance parameters that no other cables in the world could meet. It incorporates a space-based synthetic aperture radar to find sub-millimeter sized changes in the height of an ice cap to determine how much water is present.

From an RF perspective, extreme accuracy was required—any sort of error absolutely needed to be minimized, including the transmit and receive cables. All the different antenna cables had to be phase matched so the sensors could best understand exactly what they were seeing from the radar pulses. Temperature fluctuations also had to be addressed as a space-based application will go from warm on the day side of the planet to cold at night based on its orbit.

Other mechanical elements of the silicon dioxide cable that were relevant for this application included the stainless-steel jacket with a welded connector, designed to perform very well under high vibration environments such as during launch. It is also a non-outgassing material and is compliant for radiation considerations in an orbital environment. The third feature that will impact the mechanical configuration of the cable is the connector, which is application dependent.

Case Study: Hypersonic Missile Application

In this application, it was important to focus on the temperature capabilities of the silicon dioxide cable since a hypersonic missile will go through the top of the atmosphere, generating huge amounts of heat, similar to a space shuttle during re-entry.

As previously mentioned, the silicon dioxide cable itself can readily withstand those heat loads. But beyond that, one of the important requirements was phase matching at ambient temperatures. As the cable moves from cold temperatures to very hot temperatures, the phase matching between cables needs to track.

Furthermore, there are basic assumptions that likely have applied to many other specified cable assemblies that may not fit for extreme environments. For example, a shrink-down marker band that includes data such as the part number, serial number and manufacturer is a standard component in a bill of materials. However, at high temperatures, it is very likely that those marker bands will melt and create a potential foreign object debris hazard. The cable assemblies used in this application were laser marked to ensure that the important data was still included without creating any fault in the system while in operation. Custom connectors were also designed.

Medical Ablation Medical Design Outsourcing

Microwave ablation systems provide nonsurgical methods for treating internal cancers and tumors. This application requires the right cable assemblies to achieve optimum performance.

How high-frequency interconnections affect microwave ablation systems

Radiofrequency (RF) and microwave energy carry many modern messages as part of the broadcast and wireless communications but are also potentially life-saving medical tools. Within ablation systems, radiofrequency and microwave energy can penetrate a patient’s body to heat and destroy tumors, avoiding invasive surgical procedures and long recuperation times.

These systems feature advanced software and artificial intelligence (AI) methods to treat tumors with minimal damage to surrounding tissues, but they still depend on many different types of RF/microwave components. This includes coaxial cable assemblies and often-invasive antennas formed of coaxial cables. The performance of these cables is crucial because life may depend on them.

How they work

Radiofrequency and microwave ablation systems use tiny antennas or probes projected onto a patient’s body to focus electromagnetic (EM) energy on tissues to be treated.

To reach malignant tissue with adequate EM energy, small-diameter coaxial cables are used to form finely polished antennas or probes and to transfer the EM energy from a source to the antenna. Those cables should provide performance levels that help RF and microwave ablation systems destroy the targeted malignant tissues. Shielded coaxial cables with low loss at the target frequency are typically used to preserve as much of the high-frequency source energy as possible; high loss in these interconnection cables will result in RF/microwave energy lost through heating the cables rather than heating the tumor.

How they differ

The smaller wavelengths and higher frequencies of microwave ablation systems allow deeper heating penetration and wider area heating coverage than radiofrequency ablation. Ablation systems typically operate in the ISM (industrial, scientific, medical) bands at frequencies of 915 MHz, 2.45 GHz and 5.80 GHz and at power levels of 50 W (+47 dBm) or more.

That EM energy is coupled to the antenna or probe by means of a low-loss coaxial cable assembly. Higher, millimeter-wave frequencies (through 60 and 70 GHz) have been used in ablation systems for special treatment, although the difficulty of generating EM power at these higher frequencies makes the component selection for those microwave ablation systems even more critical. That is, the energy loss of a coaxial cable increases with increasing frequency.

Cable considerations

The coaxial cables used in ablation systems and other high-frequency medical electronic systems are typically flexible cables capable of wide-band frequency coverage. They should be specified carefully according to parameters that can affect RF and microwave ablation system performance. Those parameters include loss/attenuation, phase stability, shielding, passive intermodulation (PIM) and velocity of propagation (VP).

Cable loss or attenuation is a function of its dielectric and conductive materials, diameter, length and the operating frequency. Loss increases with frequency and excessive loss can cause the temperatures of the cable and ablation antenna to rise, resulting in unwanted heating of tissues along the signal path to the antenna. In some cases, it may require some form of cooling to offset the cable temperature rise caused by handling too much power with too much loss/attenuation. Cable loss is typically characterized in dB/ft. It decreases with larger cable diameters, although they are less likely to reach a patient’s malignant tissue area.

Phase must be extremely stable along the EM power path in an RF or microwave ablation system to maintain a tightly focused energy beam on a malignant tissue. Multiple cables are used in phased arrays to create focused energy on the tumor. Phase deviations can occur with cable flexure and with temperature changes, which are usually measured and compared from cable to cable in terms of ppm/°C. Phase can also vary with impedance mismatches from a nominal 50 Ω, which are measured by variations in voltage standing wave ratio (VSWR) with frequency.

Other performance parameters include the effects of propagation delays and velocity of propagation through the cables, passive intermodulation and its impact on signal integrity, and shielding effectiveness, which describes how well a cable assembly is isolated from surrounding electrical devices and energy sources.

Shielding effectiveness is key because high energy levels could interfere with other systems using the same frequencies, such as WiFi.

RF and microwave ablation systems make huge differences in the health and lives of many patients. Coaxial cable assemblies are among the high-frequency components that make RFA and MWA systems possible. When they perform properly, they can be lifesavers.

The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of Medical Design and Outsourcing or its employees.