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
In today’s unusually challenging environment, companies may need to look for workarounds to stay on track regarding supply chain and delivery. Some electronics companies are learning the hard way that supply-chain resilience is a critical qualification for doing business, whether in their own or in their business partners’ and suppliers’ operations. These lessons will change the way organizations consider procurement and production decisions for the future.
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.
Phase-Stable Cables and the Challenges of Space
Satellite communications are an indispensable part of global infrastructure, enabling real-time data transmission anywhere on earth and into space. As commercial industries increasingly work to advance and expand connectivity with powerful new 5G technology, space-based platforms and satellites will become even more critical.
The cables, connectors, and RF solutions deployed in space are integral components enabling industry to successfully move satellites, enable earthbound communications, and transmit information contributing to climate science, global security, communications relays between continents, high-speed Internet, and more. The enormity of global connection and data sharing needs is growing by the day—and the communication infrastructure’s performance is vital.
Therefore, 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 is not like designing any interconnect. Cable assemblies used in spacecraft need to brave high shock and vibration, extreme temperatures, and intense radiation. In addition, satellites have limited space for equipment, so minimizing size and weight are also key goals. Cable assemblies must be designed to perform reliably while taking up the smallest footprint possible.
Two primary considerations for optimizing RF interconnect systems, selecting the right technologies, and accommodating the unique requirements of deployment in space include smaller footprints—lightweight, high-density connections, and intricate installations in very tight spaces—and phase stability in terms of temperature and bending/motion. The critical requirements are detailed further below.
Smaller Space Requirements
Equipment used to power space technology must be lightweight, and RF coaxial cable assemblies must be designed to perform reliably in the smallest possible footprint. The high-frequency cables required for space applications also have a shorter range, requiring a dense network of antennas. Additionally, minimizing space between the cables and connectors is necessary for the interconnect system to survive the high vibration and other harsh environmental conditions.
Technology providers are working on advanced designs that accommodate these extremely restricted space constraints and rising operating frequencies to produce spaceflight connectors that successfully operate up to the 70 GHz range. This requires new coaxial cable and connector designs to deliver high signal integrity and reliability in increasingly dense environments.
One example of innovation in this area is Times Microwave’s new PhaseTrack InstaBend 047 (PTIB-047) microwave assemblies, which provide a flexible preassembled design for interconnects between RF circuit cards, modules, and enclosure panels, enabling space-efficient implementation for higher frequency systems that also need phase stability.
The new PTIB-047 is a phase-stable microwave assembly designed for a range of frequencies from DC to 70 GHz. The cable utilizes Times Microwave Systems’ proprietary TF4 dielectric material for superior phase stability over temperature, eliminating the problematic non-linear phase performance of PTFE through 15 to 25ºC. PTIB-047 is ideal for in-the-box applications with space constraints, including space flight, thermal vacuum, microwave test, and many other commercial and military applications. The cable can be bent very closely behind the connector, minimizing footprint, saving space and simplifying cable routing. This also eliminates the need to protect the back of the connector.
Tight phase control is crucial for optimizing system performance in technologies including 5G smart antennas. Two primary elements can affect a coaxial cable assembly’s phase tracking characteristic: electrical length and temperature. For example, phased array radars that have multiple antenna elements rely on coaxial cables having the same electrical lengths between the transmitter-receiver and antenna. This poses challenges on how to match the cables.
Transmission lines feed the arrays; beam accuracy depends on those cables’ phase relationships. Phase is also responsible for precision in some more time-sensitive satellite applications like GPS and radar. The phase must be accurately controlled in the components within those systems, and phase-stable cable assemblies are essential in today’s increasingly sophisticated electronics.
After that initial matching, the coaxial cables must also stay matched over varying temperatures. As temperatures change, coaxial cables do not precisely track together; the phase match degrades just slightly. That small amount of degradation can adversely affect system performance. Therefore, some cable assemblies must be optimized to minimize phase change over temperature.
The concept of phase starts with the fact that a microwave signal propagates in the form of a sine wave. For every sine wave cycle, 360 deg. of electrical length will accumulate. Millions or billions of cycles per second will accumulate in the higher frequency range of 5G applications. The wavelengths are very short, so maintaining phase accuracy across a cable length becomes exponentially more challenging as frequency increases.
Frequency, time delay, and physical properties like length, dielectric constant, and propagation velocity affect electrical length. Coaxial cables contain a consistent dielectric material throughout the length of the cable and hence have a constant velocity factor. Even though the material is consistent, environmental factors can alter the electrical properties of the cables, including temperature fluctuations, flexure, handling, twisting, pulling, and crushing that can happen to a cable during installation and maintenance.
A cable assembly also gets electrically longer as it gets colder and shorter as it gets warmer. 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 and its density changes, altering the velocity. The dielectric effects of the plastic offset and dominate the metal effects.
RF coaxial cables often use PTFE dielectric because it can operate across a broad temperature range of 50º C to 150º C) and it has a low dielectric loss. The challenge with PTFE is that the material goes through a phase transition around room temperature, causing the phase length to vary non-linearly with temperature and introducing significant hysteresis as the temperatures vary up and down. Controlling phased array antennas with PTFE-based cables is challenging in varying temperature environments. Times has experience designing cable assemblies to minimize temperature effects on phase through the use of special materials, such as cables made from silicon dioxide and TF4 and TF5 proprietary foam polyethylene blended dielectrics.
The ultimate challenge for interconnect design engineers is finding flexible dielectric materials that meet the physical requirements and can also be phase stable across a broad temperature range. PhaseTrack InstaBend 047 incorporates this proprietary TF4 dielectric material for superior phase stability over temperature, making it another excellent option for small spaces that require phase stable solutions.
Searching for and qualifying an RF interconnect supplier for space applications can be lengthy and costly. Some suppliers offer standard qualifications and documentation for basic products to simplify this process. But nothing is standard or easy in space.
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 is important to thoroughly evaluate the capabilities of an RF supplier to ensure a positive outcome.
In the design phase, consider the key considerations to be factored into any RF system that will operate in space: high-density equipment installation for minimal footprint; materials selection to withstand environmental challenges and optimize fit, weight, and durability; and phase stability for optimal signal transmission. Work with a reputable RF solutions provider who understands space’s unique requirements and can customize components to meet your application needs. A qualified provider will have experience designing custom solutions for defense, military, avionics and aerospace installations.
New RF Interconnect Solutions Power Mission-Critical 5G Networks
By Kevin Moyher
Originally Published in RadioResource Media Group
5G technologies are being rapidly deployed to deliver increased peak data speeds, ultra-low latency, enhanced reliability, enormous network capacity and increased availability. However, this requires a substantial expansion/upgrade to existing network infrastructure. For example, 5G networks must be densified to get the signal closer to users, which means more cell sites in more locations.
Small cells have emerged as the most practical means of attaining the densification needed to support the speed, coverage and latency requirements of 5G. These 5G small cell applications use multiple input multiple output (MIMO) antennas with multiple in/multiple out feeds, which substantially increases the number of RF ports. Additionally, unlike previous cellular technology generations, which focused on a specific frequency band, 5G deals with a much larger potential frequency range. For example, 4G frequency bands are typically below 3 GHz. 5G, on the other hand, can range from 450 MHz to 3.9 GHz and up to 20 – 56.2 GHz millimeter-wave (mmWave) bands for high-speed operations. 5G also encompasses unlicensed frequency bands, such as the 6 GHz band.
As a result, 5G antennas are shrinking in size as higher frequency bands are used to accommodate more extensive bandwidth requirements, which translates into more antennas and the corresponding RF cables and connectors needed to power them in a much smaller space. This equipment is also packed much closer than traditional telecom towers were years ago; at times, they are only about 100 yards apart. This requires new coaxial cables and connector solutions to deliver high signal integrity and reliability in increasingly dense environments.
The combination of smaller antennas with large numbers of cable connections also creates unique challenges related to installation, torquing, proper weather sealing and more. There are numerous variables to consider: Is it the right cable or the right port? Is that connector properly terminated to that cable? Is the coupling properly torqued down? Is the whole thing properly weather sealed? Are those cables properly captivated? Are they hooked up to the right connector and port? Are they flapping around in the wind? Are they protected from the sun, or if not, do they have the proper UV resistance?
We will discuss these concerns in more depth and provide a strategy for mitigating the challenges through the use of a bundled coaxial cable assembly solution designed for the ultra-demanding 5G small cell environment.
Bundled Cable Assemblies
A bundled cable solution can help create a 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 a single connector such as those based on the industry-standard MQ4/MQ5 design that encompasses a four-contact connector and a five-contact connector. The most common bundled cable constructions are built with inner cables that are one quarter of an inch and smaller and can be used on both non-low passive intermodulation (PIM) and low PIM interconnects. Constructions to address low PIM bundled harnesses include corrugated copper outer sheaths as well as ultra-flexible flat braid constructions.
Ensuring connectors are properly and securely tightened and eliminating any nonlinear or poor electrical contacts within the RF interconnect can also help reduce PIM issues. The MQ4 and MQ5 cluster connectors use an outer spring contact so that PIM performance is not tied to how well the tip of the outer contact is making to its mate. The connection between the male and female cluster connectors is sealed to IP67, as are the connector bodies and the transition from the cluster connector to the bundled cable. The solution is also keyed, eliminating the possibility of hooking up the wrong cable to the wrong port as the cables can only be hooked up a certain way; no torque wrenches, know-how or special technique required.
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. This 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.
As a result, 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. An example of this type of solution is the TMQ4 and TMQ5 bundled cable assemblies from Times Microwave Systems.
The bundled coaxial cable assembly solution detailed above looks better in terms of appearance and cuts a lot of labor cost, and offers a more rugged solution with better UV resistance and weatherproofing. This helps support the densification needed for the speed, coverage, high frequency and latency requirements of 5G.
When it comes to 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 solution that is ultimately easier to use, 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.
New Multiport Contacts Add High-Frequency Capabilities to UAS Applications
By Times Microwave Systems
Originally published in Unmanned Systems Technology
Today’s unmanned aerial 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. For example, the RF systems in unmanned aerial environments that once operated at frequencies of 12-18 GHz are now extending into the millimeter-wave (mmWave) frequency range of 30 GHz and beyond. As a result, system manufacturers are creating advanced new system designs to meet these evolving needs while accommodating extremely restricted space constraints.
The high-frequency RF interconnections within those systems are essential components—they must perform repeatedly and reliably and meet reduced size, weight, and power (SWaP) requirements. At the same time, the RF coaxial cables and connectors operating in unmanned aerial applications have complex mechanical, electrical, and environmental needs and must remain accessible for maintenance or troubleshooting.
The Multiport Shell Solution
SWaP equipment requirements require coaxial assemblies to maintain reliable electrical and mechanical interconnections in tight spaces and under the most severe operating conditions. However, fitting these complex systems into tight spaces can allow unwanted coupling between RF transmission lines such as coaxial cables.
High-density, modular multiport interconnect systems solve this problem by creating a smaller connector assembly with a higher interconnection density than individual coaxial connections due to integrating multiple coaxial connector contacts into a single housing. By mating a single multiport connector rather than numerous separate coaxial cable assemblies, the single connector interface provided by multiport shells reduces installation time, can ease system maintenance and testing, and increase reliability.
Solutions such as the M8 multiport connection system from Times Microwave Systems are constructed from lightweight aluminum and have advanced Reach/ROHS compliant conductive platings tested to the most severe corrosion resistance requirements. The M8 multiport system features a well-shielded structure to meet the EMI/EMC requirements of densely packed military and civil avionics systems and a design that allows for blind-mating interconnections for ease of installation. They are spring-loaded with sufficient force to ensure full mating engagement under severe vibration.
As the leader in multiport and mini-multiport shells and high-density solutions, Times Microwave Systems has also worked closely with prime contractors to develop plating materials with excellent salt fog resistance (2,000 hours) and Sulfer Dioxide resistance (668 Hours). This plating type is used on the latest, cutting-edge airframes as it is intended for use in harsh airborne and maritime environments requiring shell-to shell-conductivity.
New Contacts Provide Expanded Capabilities Within Existing Infrastructure
Unmanned aerial interconnect systems operate in harsh environments on a wide range of airframes, enduring high-shock and vibration; corrosive effects of hydraulic fluids, fuels, and other chemicals; high altitude conditions; and wide temperature ranges. These unmanned aerial systems must handle these challenging environmental conditions while packing greater functionality into smaller spaces. This requires new connector solutions to deliver high signal integrity and reliability.
The new M8M contact from Times Microwave Systems, based on time-tested multiport connector designs, is ideal for this environment. It was created for high-performance and easily survives harsh environments where high vibration, shock, temperature, and humidity can cause cable and system performance degradation.
The M8M contact is an addition to the Times Microwave Systems trusted high-performance M8 family of multiport interconnects, including the original M8 (18.5 GHz) and M8E contact (23 GHz) and lightweight, low insertion force V8 (18.5 GHz) contact. The new M8M contact works up to 40 GHz to meet the needs of high-frequency applications while using existing multiport shell infrastructure already in place. It is compatible with all M8 shells, and its unique construction makes the M8M contact excellent for use in the high vibration, harsh environments typically found in unmanned aerial applications.
The M8 family of multiport interconnect solutions has been the go-to system for many platforms worldwide throughout its more than 30-year history. Many tens of thousands of these parts are in service on a wide variety of US and allied military aircraft and have logged hundreds of thousands of flight hours. Times Microwave System also has fiber optic and octo contacts to fit into the same shells if multifamily interconnects are needed.
New RF interconnects for unmanned aerial systems must meet higher frequency requirements while retaining their predecessors’ lightweight and small form factors to meet the high-density needs of modern airframes and avionics systems. High-density modular multiport interconnect systems integrate multiple coaxial connector contacts into a single housing to create a higher interconnection density than possible with standard coaxial connectors. Building on the legacy of the trusted, proprietary Times Microwave M8 design, the M8M contact is an example of innovation that brings 40 GHz capability to multiport interconnect systems—using existing shell infrastructure already in place to maximize current investments.
Cables Keep Radar Antennas Tracking
Originally Published in Microwave Product Digest
Rapidly Advancing Technologies Create New Challenges for RF Test and Measurement
Originally Published in Microwave Product Digest
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.
New Connector Design Addresses Significant SMP Shortcomings
Originally Published in Connector Supplier
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.
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.
Making Connections in Ruggedized UAVs
By Dave Murray
Originally Published in Microwaves&RF
Military unmanned aerial vehicles (UAVs) are growing in numbers and complexity, taking on more advanced payloads with multiple sensors. Modern battlefield UAVs do everything that human-piloted air vehicles and their avionics systems once did, including electronic warfare (EW), signal intelligence (SIGINT), and surveillance, often flying at high altitudes and high speeds. Many military UAVs are designed with modular configurations to install different subsystems for each mission to optimize results.
Whether in standard or modular formats, military UAVs rely strongly on their RF/microwave interconnections to keep all systems linked, including from the UAV to the ground through demanding operating conditions. Specifying RF connectors, cables, and cable assemblies for military UAVs, especially as they increase their use of mmWave frequencies, requires an intelligent balance of many factors to keep all systems connected under all conditions.
Military UAVs vary in size and complexity according to application and mission, with larger, fixed-wing vehicles flying at higher speeds and altitudes compared to smaller, fixed- and rotary-wing vehicles used at lower altitudes in commercial and industrial applications. One of the better-known high-altitude UAVs, the RQ-4 Global Hawk, has flown at altitudes of 60,000 ft. and higher.
SWaP Considerations for UAV Components
Military requirements for size, weight, and power (SWaP) offer excellent guidance for component selection in UAVs because component weight and power consumption translate to a UAV’s operating range. In addition, components such as cables and connectors must fit into tight spaces and still be accessible for maintenance and measurement purposes.
UAVs contain many electronic parts and subsystems that must be interconnected, such as antennas, data recorders, radars, receivers, and transmitters. The cables and connectors provide the pathways for routing data, signals, and power throughout these subsystems. Any interruption in the pathways can be mission-critical, even fatal.
In general, space for components and payload in a UAV is limited, whether for military, commercial, or industrial use. The cables, connectors, and cable assemblies that provide interconnections within a UAV must meet tight space requirements while maintaining high performance and reliability. These interconnections have to satisfy challenging mechanical and electrical requirements within a UAV capable of enduring severe environmental conditions.
Choosing Cables and Interconnects: Where to Begin?
A practical starting point for sorting through coaxial cable interconnects is determining if they will even fit within the airframe. Smaller cables may fit where space is limited, adding little to the total weight of the UAV, but they may lack the performance to meet the electrical requirements of its electronic systems, so mechanical and electrical needs must be balanced.
Ideally, once installed, coaxial interconnections can be readily accessed for testing and maintenance purposes. UAVs with modular sensor systems will require access to interconnections for different modules used within the airframe.
Cable selection requires a balance of the mechanical, electrical, and environmental requirements for a UAV’s systems. Maximum cable diameter and weight are practical starting points when sorting through available cable solutions. The coaxial cable should exhibit low loss across a frequency range of interest, which will depend on the length and diameter of the cable.
The cable’s insertion loss and return loss (VSWR) also will be affected by the choice of connectors and how well the cable assembly and connectors are constructed. Low loss is particularly important for cable assemblies used at higher frequencies since signal power is limited at mmWave frequencies.
In addition to cable diameter and weight, the flexibility of a coaxial cable assembly is essential when determining whether a particular assembly can fit the needs of a UAV’s interconnections. Interconnect flexibility can be gauged in terms of its minimum bend radius, which is a function of a cable’s construction. Minimum bend radius effectively defines the space required for the smallest change in a cable’s direction.
Weathering High-Stress Conditions
High-frequency interconnect cable assemblies for military UAVs face severe conditions while in flight due to changing weather and stresses caused by high-speed operation. Some UAVs developed for high-altitude operation include hypersonic capabilities with speeds reaching Mach 5 and above. These speeds result in high-temperature environments for the UAV’s electronic components and systems, which must operate reliably at these higher temperatures.
Because the interconnections are such critical components, cables and connectors for military-grade UAVs are designed for operating temperatures as high as +300°C and total operating temperature ranges as wide as −65 to +300°C. Even the 300°C limit is being challenged; thus, Times Microwave Systems (TMS) has been asked to develop materials for its cables and connectors to handle these new challenges.
RF/microwave interconnections in military UAVs, especially those with phased-array antennas, require high phase stability with temperature. Phase-matched cable assemblies are typically used in antenna systems where phase is used as a beamforming and tuning parameter and in multiple-input/multiple-output (MIMO) antennas that combine the contributions of multiple antennas to send and receive high-frequency signals, often with wide modulation bandwidths.
High-altitude (typically 50,000 ft. or more above sea level) UAVs often operate in conditions that expose their components to near-vacuum environments, resulting in moisture-absorption problems when it returns to sea level. This “water in the cable” affects the interconnect amplitude and phase characteristics of the cable’s conductive metals and dielectric insulators and may result in significant degradation and failure of an electronic systems. As a preventative measure, coaxial cables designed for military UAVs, especially those for high-altitude operation, usually include some form of environmental seal against the effects of vacuum-like environments.
The mechanical, electrical, and environmental performance levels achieved by a UAV’s coaxial cables also must include its connectors as they contribute to the SWaP levels. Connectors are typically designed for ease of installation and minimal mechanical and electrical performance degradation. For UAV applications, the high-performance levels must be maintained at high shock and vibration levels.
The quality of a coaxial connector’s machined components, as well as performance and reliability, are impacted by how well the connector is attached to the cable and the effectiveness of its locking mechanism in a mated pair of connectors. Connectors can be soldered or crimped to a cable, with soldering the more labor-intensive approach but providing a robust mechanical attachment with little performance degradation over time. An effective plated finish on a coaxial connector also can contribute to reliable and consistent long-term performance.
Due to the modular architecture of some UAVs, some coaxial connectors must endure many mate-demate cycles for changing of function modules within the UAV. In such cases, a connector’s mate-demate lifetime needs to be evaluated along with its mechanical, electrical, and environmental performance parameters to achieve the best fit within a particular UAV. Oftentimes, high-frequency, high-performance blind-mate connectors are used in UAVs for this purpose.
Practical UAV interconnection solutions are typically available as cables or cable assemblies constructed according to precise lengths and designated connectors. For example, TMS’s MILTECH flexible cable assemblies (Fig. 2) from Times Microwave Systems feature excellent shock and vibration resistance and good phase stability over a wide operating temperature range (−65 to +200°C). They’re manufactured to applicable military standards with tight cable/connector interface control to achieve the hermetic seal needed for high-altitude flight.
The cables are constructed with polytetrafluoroethylene (PTFE) dielectric, a solid silver-plated copper center conductor, and a silver-plated copper shield for protection from electromagnetic interference (EMI). Furthermore, they’re factory-terminated with a variety of coaxial connectors.
To meet the tight space requirements of different UAV systems, MILTECH cables come in various sizes/weights, including 0.130-in. (3.30-mm) diameter cables with 0.650-in. minimum bend radius and 0.175-in. (4.45-mm) diameter cables with 0.875-in. minimum bend radius. The smaller-diameter cables can be terminated with 2.4- or 2.9-mm connectors for use at mmWave frequencies. The cables feature high moisture resistance and vibration resistance according to MIL-STD-202 requirements and high shock resistance per MIL-E-5272 requirements.
For tight UAV fits requiring cables bent close to the connector, TMS’s INSTABEND 047 cable assemblies (Fig. 3) provide low-loss propagation of signals up to 62 GHz in the tightest spaces. To ensure high-quality attachment of connectors to cable, they’re only available as complete assemblies.
An INSTABEND 047 cable assembly with an outside diameter of 0.10 in. (2.67 mm) provides a minimum bend radius of 0.3 in. (6.4 mm). Light in weight for UAVs, these cable assemblies weigh only 0.01 lb./ft. (0.02 kg/m) and are available with several different connectors depending on frequency range. They handle temperatures from −60 to +125°C, are shielded to −90 dBc, and rated for voltages to 100 V.
When phase must be tightly controlled, PhaseTrack cables and cable assemblies developed by Times Microwave Systems are well-suited for that parameter, coming in a variety of diameters with different connectors. A 0.108-in. diameter cable (Fig. 4) features a cutoff frequency of 80 GHz and a minimum bend radius of 0.550 in. The cable is constructed with proprietary TF4 dielectric and doesn’t suffer the phase variations with temperature common to cables with PTFE dielectric.
PhaseTrack cable assemblies fit ground, sea, airborne, and space platforms. They’re available in many versions, including a silicon-dioxide (SiO2) dielectric for applications with temperatures exceeding +1000°C.
Maintaining connections under high shock and vibration levels common to a UAV while being easy to mate requires a coaxial connector with a simple but effective locking mechanism. The TLMP push-on locking connector from Times Microwave Systems (Fig. 5) was designed with the small form factor of the popular SMP push-on connector but with improved mechanical, electrical, and environmental performance.
The TLMP connector, which is usable to 60 GHz, has a unique mechanical design that supports high-pulsed-power, high-voltage applications. Its latching mechanism achieves improved mating retention compared to an SMP connector even in the high shock and vibration environments of military UAVs. The connector’s slots are entirely covered with its mating part for improved EMI and EMC performance compared to an SMP connector. Connections must maintain high EMI and low levels of signal leakage to prevent an adversary from identifying a military drone in flight.
For UAV interconnect applications that don’t require a hermetic seal or enhanced phase stability, Times Microwave Systems’ LMR and TCA cables and cable assemblies can be practical options. LMR cable assemblies provide flexibility to enable tight fits while LMR LW cables feature an aluminum braid shield for effective shielding in low-weight cable assemblies usable through 8 GHz. TCA cables and connectors have long served commercial avionics systems as flexible interconnect solutions, offering a combination of light weight and durability through 5 GHz and higher.
High-Density RF Solutions
Technology providers are creating advanced new wireless system designs to accommodate extremely restricted space constraints and rising operating frequencies. These solutions need new coaxial cables and connectors to deliver high signal integrity and reliability in increasingly dense environments. Industries requiring high-density RF interconnect systems include 5G, space, and avionics.
Antenna densification is required to deliver increased peak data speeds, ultra-low latency, enhanced reliability, enormous network capacity, and increased availability for 5G. Its specifications are based on MIMO antennas, which are shrinking in size as higher frequency bands are used to accommodate larger bandwidth requirements. This translates into more antennas in a smaller space.
Small cells are a great example of this as they are packed much closer than traditional macro-telecom towers, often only 100 yards or so apart. Demand for high-density cabling solutions to accommodate the necessary connections in smaller, more compact installations will continue to grow. This includes high-density interconnect solutions, such as multiport connectors and coaxial cable bundles.
Bundled coaxial cables use a coaxial feeder cable bundled under a common outer jacket. This innovative design acts as the perfect flexible antenna jumper for applications requiring multiple runs, such as 5G small cells located on towers or building-top sites.
The increasing demand for high coverage antennas has also led to substantial growth in the number of ports on antennas and RF devices. Hooking up the right cables to the correct ports, weather sealing, and torqueing are all concerns in this scenario. Multiport connectors can be used in this instance to reduce the number of connections.
This type of “RF cluster connector” incorporates multiple RF ports in one connector, enabling antennas to provide more ports without the need to increase dimensions. There are standardized designs that encompass a four-contact connector and a five-contact connector including our TMQ4 and TMQ5 multiport connectors. These can significantly reduce the number of cables that have to be hooked up, saving a lot of labor and creating a more rugged solution. They also make the assembly more weatherproof and UV resistant and reduce the need to worry about coupling torque.
Equipment used to power space technology must be lightweight, small, reliable, and resistant to high-shock and vibration, radiation, and harsh/extreme temperatures. RF coaxial cable assemblies must be designed to perform reliably in the smallest possible footprint. The high-frequency cables required for space applications also have a shorter range, requiring a dense network of antennas.
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 cable can be bent around tight corners and very closely behind the connector, minimizing footprint, saving room, and simplifying cable routing in tight spaces.
Avionics applications also have limited space as they accommodate more application needs throughout the vehicle. In the past, it may have been common to have 12 antennas on a commercial airframe, but there are now about 50 or more. The increasing number of antennas in aircraft environments also creates the need for more electronic boxes and their connections.
Additionally, minimizing space between the cables and connectors is necessary for the interconnect system to survive the high vibration. InstaBend is also a great fit here. Our Instabend assemblies withstand high vibration and other harsh environmental conditions, ensuring a consistent, long-lasting connection.
Additionally, a new generation of locking miniature push-on connectors, such as our TLMP™, is specifically designed to address the shortcomings of SMP-style connectors. The TLMP connector retains the small form factor of the SMP for highly dense environments but adds improved environmental, shielding, and power capabilities, with a frequency range from DC to 60 GHz. A positive locking feature with visible green (locked) and red (unlocked) color coding prevents de-mating under vibration and shock.
Key Considerations for Coaxial Cables in Space
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.
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.
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.
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.
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.
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.
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 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.
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.
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.
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