Author Archives: Kelly Foster

M8M Multiport Connectors

Achieving High Density in Mission-Critical Circuits

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 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 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 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.


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.


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.


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

New Connector Field Installations Improve System Reliability

Connector Installation

New Connector Field Installations Improve System Reliability

By Kevin Moyher

Here is a short case history demonstrating a solution for reliable field-installed connectors use in high reliability wireless E911 systems

Across the country, CDMA, TDMA and GSM wireless communication sites are being upgraded to meet the requirements of the FCC’s Enhanced 911, or E911, mandate. Phase II of this ruling requires that network-based wireless location systems locate a wireless phone user to within 100 meters 67 percent of the time, and to within 300 meters 95 percent of the time. The quality and reliability of these systems is paramount; people’s lives may depend on it. Applications for this system are personal security, medical alerts, child tracking and accident response.

An Example of E911 Equipment

True Position is a leading supplier of the complex equipment that is integrated into cellular and PCS base stations to give them user location capability. True Position utilizes UTDOA (Uplink Time Difference of Arrival) technology to locate a subscriber’s cell phone. The LMU (Location Measurement Unit) is installed at each cell site. This equipment passively overlays the existing wireless network, sending critical data back to the operator’s Mobile Switching Centers where LCs (Location Calculators) perform the multipath mitigation algorithms. When a wireless phone user whose carrier employs True Position’s equipment dials 911 and activates the E911 network, the equipment in the area surrounding the caller is activated and begins to perform the complex calculations necessary to pinpoint the caller.

The reliability of this equipment is critical, and it has been optimized and ruggedized to perform with high reliability. However, there are only so many safe guards and safety measures that can be incorporated into the components themselves. The ultimate reliability of this system depends on the quality of the interconnecting cable runs. As shown in the photos of Figure 1, the E911 hardware has to be connected to each of the transmit and receive antenna runs, requiring multiple short interconnect cables. These cables are built from small core low-loss, flexible 50 ohm coaxial cable. True Position minimized some of the installation variables by using the QMA interface for these interconnecting runs. This interface can best be described as a high performance, quick connect SMA. The adoption of this interface eliminates the need for threading of small coupling nuts and the concern for achieving the proper mating torque.

Times Microwave has contributed to high performance and reliability of these systems, starting with the basic requirements of high quality cable and connectors with very good return loss. However, since the layout of every base station is different and the lengths of the interconnect cables vary accordingly, the cables must be cut and terminated in the field. This reality prompted the design of a series of EZ (spring finger center con- tact) connectors that interface with Times’ LMR-240 cable (Figure 2). Though QMAs are the dominant interface in the system, SMA and Type N connectors are also widely used. These EZ connectors eliminate the need for soldering in the field and solve the issues of pin height and pin to core gap. These three variables are often the largest contributors to inconsistency in the performance of field terminated interconnect cables.

The right angle EZs employ a unique design. Many spring finger right angle connectors have a 90° swept center pin with a mitered outer conductor. This design offers ease of termination at the expense of return loss. Times has taken the typical soldered right angle design and improved upon it. The straight brass center pin has been replaced by a straight beryllium copper pin that is bifurcated at the back end with a lead-in for the cable center conductor. This configuration has the ability to fine tune the impedance across the right angle. Where typical EZ right angles have a return loss weakness over a properly designed right angle solder connector, this new design actually has an advantage: excess solder build-up is no longer an issue. Going a step further with this design, a stop is placed inside the connector so that the pin can not be over extended beyond the center pin.

Optimization of the field terminated cables goes beyond connector design and includes the development of two easy-to-use termination tools. The first of these is a “one-step” cable stripping tool (ST-240EZ). Many small coaxial cable prepping tools are generic tools which are completely adjustable. These tools are capable of being adjusted to work with different cables but can be a real minefield in terms of potential termination problems (i.e., nicked outer braids, nicked center conductor, crushed core, improper strip lengths, etc.). The ST- 240 is a completely customized tool. The cable slides into a cable slot until it hits a stop. The blade package, containing two hardened alloy blades, is then released onto the cable, the index finger is placed through the loop at the end of the tools handle and the tool is spun clockwise around the cable for three to four full revolutions. The tool is then grasped as close to the cable as possible and pulled away from the cable, exposing the center conductor and tinned copper round wire braid.

This tool assures that the cable is stripped to the proper dimensions every time. It preps the core square and clean without crushing it or rip- ping the outer conductor and it preps the center conductor clean without nicking. The most important function which the tool performs is to expose the braid without nicking it. This is a very important requirement in the termination process that often gets overlooked. The braids on these small core flexible cables are of a very small diameter and a slight miscalculation with the pressure applied to a knife or a slight mis-adjustment of a variable stripping tool could effectively wipe out half or more of the braid, resulting in poor connector retention. The introduction of these EZ connectors for LMR-240, and the simple tools to assist with their termination, has created a nearly foolproof choice for the field assembly of short low-loss  interconnect cables.

Interpretation of Electrical Test Data with Regards to Microwave Cable Assemblies

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

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

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

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.


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

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

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.


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.


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

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.


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

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.


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.

Don’t Overlook the RF Connector

Broadband Wireless

Don’t Overlook the RF Connector

Technical Primer: Using the Proper Connectors Can Be Critical in High-Frequency Applications

By Kevin Moyher

Connectors on an RF assembly are often taken for granted. In many cases the designer is satisfied if he has found a connector of the proper interface that will physically fit onto the cable that he intends to use. Impedance uniformity across a cable assembly is paramount in the efficient transmission of RF energy. The cable assembly is basically only as good as its weakest link. The time and money spent on high-quality, low-loss cable can be wasted if there are large impedance mismatches within the connectors, at the connector-cable interface and at the connector-device interface.

The Connector and Wave Reflection

Ideally, the RF connector will have a uniform impedance across its entire electrical path and a VSWR (voltage standing wave ratio) rating of 1.00:1. The VSWR value of a connector is the expression of the percentage of the input signal that is reflected back toward the source due to mismatches within the connector. This VSWR value can also be used to express the percentage of reflections across an entire assembly.

A uniform impedance across the connector, the cable and the connector-cable interface will allow the input signal of an RF transmission line to be efficiently transmitted to the output. In this case, reflections created by impedance mismatches will be nonexistent, and the losses across the assembly length will be strictly a function of the resistance of the conductors, the electrical properties of the dielectric and the shielding of the cable.

Connectors with greater impedance mismatches will have higher VSWR values associated with them. These VSWR values can be directly correlated with a value called mismatch loss (for example, a VSWR value of 5.85 has a mismatch loss of 3.021 dB).

The overall insertion loss for an assembly can be determined by calculating the theoretical
attenuation of the assembly and then adding all of the mismatch losses that would be associated with the assembly (i.e. cable, forward connector and aft connector). This calculated value represents a worst-case scenario. It would become reality if the peaks of the incident wave and all of the reflected waves were in phase with each other. This scenario is possible, but unlikely. However,
it is almost certain that the overall insertion loss of the assembly will increase as the reflections caused by mismatches along its length increase.

A perfect connector with a 1.00:1 VSWR is not possible, or I should say, it is not economically
viable. There are line-size transitions that are taking place within the connector. There are many variables involved in optimizing these line-size transitions. An abrupt transition may work well at lower frequencies, but this transition must be compensated when working at higher frequencies.
This is not an exact science. However, experienced connector designers can use time domain reflectometry to map the impedance mismatches across the connector. They can then improve the uniformity of the impedance across the connector. The art in doing this is not simply in finding a way to properly compensate the connector but in doing it in such a way that it can be produced economically.

VSWR Performance

VSWR performances of three 30-inch LMR assemblies are shown in Figures 1 and 2. The three graphs in Figure 1 display the performance of LMR-400 assemblies terminated with type N male connectors. The bottom graph of Figure 1 shows the performance of an assembly that was constructed with Times Microwave Systems’ connectors, while the top and middle graphs display the performance of assemblies constructed from connectors supplied by two other leading connector suppliers.

The first thing that comes to mind when looking at these traces in Figure 1 is that the nodes are similarly shaped and very cyclical, indicating that the cable itself has a very uniform impedance. In the event that the cable varied in impedance, the trace would look much more ragged. The VSWR trace of a cable with very poor impedance uniformity would look almost like random noise.

Based on this information and the fact that each of these 30-inch assemblies was made from the same lot of cable, we know that the steadily increasing VSWR with frequency in the middle graph of Figure 1 and the high VSWR in the midband shown in the top graph can be attributed to reflections
due to impedance mismatches within the connectors.

These three curves in Figure 1 demonstrate how the size and material transitions within a particular connector design may be compensated to perform well up to a certain frequency. It is also possible to design a connector that may perform very well in a particular band but reflect a larger percentage of the input signal at frequencies both above and below the designated band.

Figure 2 compares three 30-inch LMR- 600 assemblies. The assembly represented in the bottom graph of Figure 2 has been built with Times Microwave Systems’ EZ-600-
NMH connectors. The assemblies represented in the top and middle graphs of Figure 2 have been built with connectors from two other leading suppliers. The top and middle graphs indicate good performance in the low band, excellent performance at midband and very quick roll off in the high band. The assembly represented in the bottom graph of Figure 2 indicates good performance across
the entire band, with excellent performance at the high ISM (Industrial Scientific Medical) band.

Connector Design for High Frequencies

It gets increasingly difficult with connectors, as with cable, to design, build and maintain the tight process controls that are necessary to achieve a high level of performance over a broad frequency band. It’s especially difficult as the frequencies climb well beyond the 1 GHz level, such as in the
5.8-GHz ISM band. Although it is possible to optimize connectors to perform well in certain bands, it is rarely viable from an economic standpoint.

Most connectors are rated for broadband performance to a specific maximum frequency. Unfortunately, most manufacturers of commercial RF connectors have not been able to keep up with the improvements that would be necessary to obtain reasonably good performance at the 3.7- or 5.8-GHz level, never mind optimal performance.

As little as three years ago, most applications were operating below 1 GHz; as recently as two years ago, most applications for commercial cable and connectors were operating below 2 GHz. It is these cellular and PCS (personal communications service) bands for which most connectors were designed. Someone working in these bands could basically pull any connector off a shelf and it would be a pretty safe bet that the performance would at least be respectable. Most connector manufacturers were slow to understand that a connector that was sufficient in a PCS application at 2 GHz may not meet the requirements for a 2.4 GHz application in the ISM band.
The proliferation of data applications in the ISM bands has placed certain demands on connector performance. These bands are unlicensed, and therefore the Federal Communications Commission has placed power limitations on transmissions in these bands. The need to be assured that there is a
sufficient transmit signal — but at the same time, making sure that the transmit power never exceeds the maximum allowable power — has, in many cases, created a demand for low-loss cable assemblies that are consistent and predictable in performance.

The nature of data transmission itself has also pushed systems to reduce noise levels to their absolute minimum. The best way to do this is to minimize the power levels of the system. Hence, there’s a need for low-loss cable, and, just as importantly, low-loss assemblies. As an added challenge, some of these systems are now operating in the 5.8- GHz band.

A desirable feature to have in any connector, and especially in one that must be field installed, is a captivated pin. The pin may be of a spring-finger design and permanently pressed into the dielectric or it might have a shoulder on it that will make positive contact with the bottom of a counter bore in
the connector dielectric. It’s not a stretch to imagine that the pin height of a connector with a noncaptivated pin, when installed in the field, may be 10 to 20 mils off. This error will create shifts in impedance throughout the connector, especially if there are many diameter transitions in the pin.

The Cable Design Factor

There are an enormous number of 50- ohm coaxial cable designs available. The designs encompass standard RG designations, as well as specific requirements that have arisen over the years. These designs have been devised to optimize certain parameters of the cable, such as attenuation, impedance uniformity, velocity, time delay, diameter, bend radius, flexibility, temperature range of operation and weight.

These parameters are optimized by varying center conductor, dielectric, outer conductor, and jacket materials and sizes. Optimization is also accomplished by varying the processes by which the cable is produced. Although most of these cables are 50-ohm cables, many of them present their own unique physical considerations when they are terminated with a connector.

Times Microwave Systems makes a variety of 50-ohm coaxial cables, more than any other manufacturer. The product line includes RG cables and the LMR line of low-loss flexible cable that is widely used in telecommunications and has become the accepted standard for wireless data.

The Connector-Cable Interface

There are an enormous number of connector interfaces that are in use today.
However, in wireless communications more often than not, we find ourselves working
with SMAs, TNCs, Ns or 7/16 DINs. The need for economic solutions in the development
of wireless infrastructure requires us to use the smallest diameter cable that will keep us within our loss budget and meet any other requirements that the system will place on the cable.

Factoring in the need to work with the smallest cable available, it can be quite a task to find the ideal connector for a particular cable. Considerations include the variety of cable designs, the number of connector interfaces that are dealt with, and issues such as gender, straight or right angle, clamp or
crimp, connector material and plating. Additionally, most cable manufacturers do not design or build connectors, and most connector manufacturers do not design or build cable. Hence, a certain level of frustration can be expected.
For purposes of discussion, we will assume that we are working with cable that has a uniform, 50-ohm impedance. Also, we assume that our connectors have a uniform impedance across their length (including the compensation necessary to carry out the line-size transition from the interface to the
core diameter that is being considered). At this point, the most important consideration is the mechanical fit between the transfer body of the connector (the effective outer conductor) and the outer conductor or shield of the cable itself. Ideally, this interface will be smooth and mechanically intimate around the entire 360-degree circumference of the connector.

Some connectors are designed to snugly fit over the outer shield of a cable. Other connectors are designed to fit snugly over the dielectric and have the shield or outer conductor crimped or clamped to the outer surface of the transfer body of the connector. In any case, the inner diameter of the
outer conductor must be maintained as best as possible when making the cable-connector
transition, and this transition must be mechanically sound. It doesn’t do any good to have an assembly that will perform reasonably well on a workbench but deteriorates quickly when exposed to real-life situations such as wind, vibration and temperature shifts.


As the frequencies of new applications continue to rise and performance requirements
become increasingly demanding, the connector must be looked at closely. Factors include the mechanical variables that will affect overall electrical performance, performance
under extreme conditions and the long-term ability to withstand the environment. Also, each connector has its own impedance characteristics similar to a fingerprint. Various connector designs will be associated with different VSWR values at a given frequency, and, in some cases, may have a significant impact on the overall insertion loss of a microwave assembly.

About the Author:
Kevin Moyher is a sales engineer at Times Microwave Systems. Times Microwave Systems is a division of Smith Industries PLC and has been involved in the design and manufacture of high performance coaxial cables for more than 50 years.

The New TCA: Solutions for Avionics Installations Webinar Summary


With a long history of serving the aviation community, we understand our customers’ needs for reliability, quality, and delivery. As a result of that decades-long heritage, Times Microwave designed a complete system of cables, connectors, tools, and accessories that make installation easy and clean—the TCA product family. Carrie Obedzinski and Kevin Moyher, two leading industry experts, discuss the challenges and requirements of airframe installations. From reduced inventory and foreign object debris (FOD) to time and cost savings, customers around the world have tested and approved thousands of our TCA assemblies.

Watch the video or read the session notes below.

Session Notes

Times Microwave Systems’ engineering and manufacturing capabilities enable us to deliver RF products that meet the most demanding and unusual aviation requirements, including customized solutions and product design, installation, regulatory compliance, and performance improvement. Most importantly, with fully integrated manufacturing production, we have all the necessary assembly and testing capabilities in-house. We deliver RF interconnect solutions from conception through flight testing and production.

This webinar will detail some of the challenges and requirements of airframe installations and present some excellent solutions for making them easier, more efficient, and reliable.

We have been manufacturing our three most popular 50 Ohm aviation cables, spanning from the HF to the KA band, for many years. Times’ LMR®-FR, for example, is one of the most popular products for wireless applications. It is very easy to terminate in the field and comes with a complete line of connectors and tooling. Its fire-retardant FR jacket meets FAA flame test requirements. MaxGain® is our higher-frequency band cable; it’s an outstanding solution for KU and KA-SATCOM feeders. TCA, the focus of this webinar, is our high-performance cable used for higher temperature ranges up to 200°C.

There is some overlap between our avionics solutions because multiple products are suitable for certain applications. Times’ experienced engineering team members can help you determine which product to use based on your requirements such as flexibility or in-field assembly; or we can even create a new solution if needed, as we specialize in custom-engineered cable assemblies.

The TCA Product Line

We have been listening to our aviation customers—visiting them on site to understand what is important to their companies. Maintenance and safety are typically mentioned by installers, procurement and management alike.

Our aviation customers are also focused more than ever on minimizing waste, improving efficiencies, and reducing costs and inventories, including time savings in manufacturing processes and MRO aircraft installations. To satisfy these priorities, we have expanded our TCA product line to include a complete end-to-end RF interconnect solution for avionics, including cables, modular connectors, tooling and a pulling nose tool.

The TCA product line features Times’ lightweight, low-loss, high-temperature, highly flexible TCA cable, ideal for meeting avionics’ critical electrical and mechanical performance requirements for applications including satellite communications, collision avoidance, navigation, and more. TCA is great for routing cable through tight runs. It is an industry-standard construction and can satisfy an equivalent drop-in replacement on many specs. There are multiple shielding layers to reduce interference.


The TCA flight-friendly modular connector system makes terminating the cable quick and easy while ensuring optimal electrical and mechanical performance. Modularized design enables the user to install the connectors with the configuration that best fits the final system.

The TCA connectors have 2-Nickel or bi-metal plating for excellent corrosion resistance and optimized VSWR performance. No braid trimming is needed during assembly, so this system helps reduce foreign object debris (FOD).

Once installed, there are many different standardized front ends to choose from. TCA’s modular concept also helps improve troubleshooting and repair—the user can take off the connector fronts and change them out, instead of completely removing the entire connector. Because the system uses the same intermediate heads, you can reduce inventory costs and risks, buying the parts you need for numerous connector configurations. They also meet IP 67 standards for moisture ingress.

Unique, All-in-one Prep Tools

  • Maintenance personnel and installers sometimes work with razor blades and knives while hanging upside down, trying to fit multiple connector assemblies and terminate them inside the aircraft. The TCA product line includes unique, all-in-one prep tools for simple, safe and repeatable cable termination including the ST-3520, ST-31156 and ST-3112. Users can also save time by pre-terminating the assemblies with the cable entry and using TCA’s reusable pulling eye to “fish” the assembly through the fuselage of an aircraft. This helps cut down on tooling, debris and installation damage.

TCA tools will trim the cable to a proper conductor and perfect exposure length for modular connector assembly. The tools are supplied with a snap cover to help maintain control of cable debris for cleanroom and airplane worksites. It’s another way to help reduce the likelihood of FOD.

The tools help ensure repeatable prep because all assemblers and installers use are using a standard tool and process to ensure consistency in both electrical and mechanical performance.

The TCA product line ultimately helps make the installers’ job easier, safer, quicker, and more effective with less tooling needed, less debris, and repeatable performance terminations.


  • We have a question about the modular connections. You mentioned using Loctite. How would you disconnect that in the field?
  • I have concerns using a razor blade against the center conductor. Are there concerns about damaging the cable?

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

medical rf system

The Challenges of High Power in RF Applications Webinar 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.


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.


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!

RF Interconnect Solutions for Complex Antenna Installations Webinar Summary


In this session, Dave provides an overview on how to design solutions for challenging airframe antenna applications. In addition, Dave discussed the nuances of working within the aviation space, and how Times Microwaves’ aircraft applications are designed to work in the challenging conditions that military-grade aircrafts endure on a daily basis. For example, the unique properties of a Times Microwave military/tactical-class feeder antenna lineup is designed to be equal parts durable and repairable for quick fixes on popular military aircraft like the C17.

Watch the video or read the session notes below.

Session Notes

A typical aircraft antenna installation involves a two-port antenna with a TNC female and an N female, a double plate matching the arc of the aircraft, and two cable assemblies. Once mated, the antenna is attached to the aircraft, and the two connectors attach to the antenna. However, this is 1960s technology. Let’s see what we can do about that.

There are standard technical considerations in terms of maintenance and access with an antenna mount located on an aircraft:

  • The environmental seal, especially on lower antennas
  • Mating life (and potential disconnections)
  • Electrical performance over vibration

To address these concerns more effectively, let’s discuss a blind mating of the same antenna. This involves identical double plate and cable assemblies, but the N and the TNC connectors are replaced with blind mate versions. This eliminates the coupling nut and the lock wire scheme in favor of a captive spring column.

The alignment sleeves are attached to the antenna, one N and one TNC. Once these are mated, it turns into a blind mate-able surface. This stainless-steel alignment sleeve has turn rings, one that seals the threads from the outside in, and another that seals to an interface. To make this mount, the receiver sleeve is put up and then mounted to the doubler plate itself, and based upon the location and the height of the antenna, the zero position of the receiver sleeve is determined. Each of these receiver sleeves has a C-clip on it to hold it in place and the base connector threads directly onto it.

Environmental Sealing and Mating Life

Anytime there is a male, female TNC or a male female, as the connectors mount, they typically wear out at well under 500 mates. Additionally, after 500 mates and de-mates, a lot of metal debris has been generated that has likely filled that interface, resulting in potential electrical issues.

With the blind mate solution, as the nose cone is closed, the four alignment sleeves engage into a bracket that has a slight rotation on it. The springs engage as the nose cone is tightened in place. This type of antenna junction has been tested for wear and tear, resulting in 5,000+ mates with no failures.

Vibration and Electrical Performance

This example details an F35-C carrier landing condition with a significantly high vibration profile. On the right-hand nose door, there is a microwave landing system and an integrated carrier landing system. Each antenna contains a connector. In a normal test environment, a Band Aid connector such as a TMA can be attached. This is a three or four prong mated connector that enables antenna testing, antenna patterns, etc.

However, these landing system antennas are located on the inside of the nose door on a low observable aircraft. To find an airport or a ship, that nose door has to be opened—and this happens at up to 300 knots, which is equivalent to about a Class Five hurricane in the internal cavity. The problem with mounting a typical right-angle connector to one of these antennas in that kind of a vibration profile is that they tend to break.

Instead of continuing to mount the antenna the same way, we came up with the idea of using a multiport connector instead. Once the antenna has mated, it gets an environmental seal that engages the amount necessary for tolerancing. However, no motion is generated as a function of the vibration profile—it’s basically all neutralized at the bracket. The result is a very high performing RF interface at 300 knots in the carrier landing environment.


Following are the questions that were asked by the audience:

  • Can any antenna be made into a blind mate antenna?
  • What if I want to put a gasket under my own antenna? Does the blind mate allow for that additional thickness?
  • Are blind mate connectors recommended for high PIM requirements?
  • Is most cable compatible with a blind mate?
  • Could a blind mate be used with a Mil-Tec line or a Phase Track line?
  • How much height is added to the blind mate or how much does a blind mate system add to the antenna?
  • What about other applications, for example, or LRU boxes?
  • Is there an application in space launch?
  • Can you speak to tolerances of vibration levels?
  • Are there drawings available of designs that have been done?

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


RF in Space: 5 Steps to Find the Best Interconnect Supplier Webinar 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!


RF Applications: The Big Picture Webinar 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.


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.


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.


Reliable Solutions for Test and Measurement Webinar 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.


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!


Phase 102 Webinar 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!


Phase 101 Webinar 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!


Outside the Box Solutions for Inside-the-box Applications: Webinar 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 600oC 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.


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.


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!


Medical Applications: The Future of Healthcare Webinar 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.


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.


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!

Solutions for Low PIM Applications Webinar


This presentation, Solutions for Low PIM Applications, was originally delivered in August 2021 as part of Times Microwave SystemsTimes Talks webinar series. Following is a session summary of the talk given by Carrie Obedzinski, distributions sales manager for Times Microwave and Kevin Moyher, product manager for Times Microwave.

As the telecom industry moves to 5G, the need for small cell and DAS systems multiplies. Antenna densification required for 5G is creating a need for smaller and smaller, flexible, low PIM cables. As more 5G networks come online, demand for cabling solutions that can accommodate all the necessary connections in smaller, more compact installations, while minimizing PIM, will continue to grow. The webinar details how cabling solutions are designed at Times Microwave to meet these advanced requirements and enable the next frontier in telecommunications.

Watch the video or read the session notes below.

Session Notes

What is Low PIM? Why Does it Matter?

PIM is short for Passive Intermodulation, which is a type of distortion that may occur in passive, non-linear components such as RF cables and connectors. Essentially, when two or more frequencies exist on the same cable, there is a chance that a third frequency will form. Cables and connectors play a large role in PIM, which can occur because of something resistive in the interconnect, the junctions between different types of passive components such as the connector and cable, ferrous materials, inadequate tolerance, poor torquing, etc.

While PIM is an issue for almost every wireless system, it is more noticeable in cellular applications such as 5G because the frequency bands used are very close to each other. PIM can create interference that limits receive sensitivity, lowering the reliability, data rate, and capacity of the cellular system. This can also result in dropped calls.

PIM is also a great criteria for measuring the quality of an interconnect, especially mechanical integrity and VSWR (Voltage Standing Wave Ratio), which is a measure of return/insertion loss. In an ideal system, 100% of the energy is transmitted. However, if there is a cold solder joint or air pocket in the solder, loose connections or a related issue, the VSWR return or insertion loss may not be detected—but it will be picked up with passive intermodulation. This is another reason that carriers and integrators look for passive intermodulation.

What Can be Done to Minimize PIM?

First, ensure that the right materials and platings are used. Next, eliminate any nonlinear contacts within the RF interconnect, and any poor electrical contacts. This can be caused by loose parts, parts with rough surfaces, oxidation, residual flux, etc. If conductive material is used, particulate on the face of the dielectric or within the interface itself is going to cause a problem and may actually move directly on the connectors when installed.

What Type of Testing is Performed to Ensure Solid Performance?

In the telecom industry, it is pretty much standard to place two 20-watt signals on the RF interconnect. This is done to look at the third order harmonic, typically the harmonic of the largest magnitude. Most testing requirements are looking for 153 dBc-155 dBc or better. At Times Microwave, we look for 160 dBc or better.

There are two types of tests. The first is a static test, basically a bench test. If the right materials, and platings are used and the connectors are properly tightened, this is a fairly low bar to meet. The second test, a dynamic test, is much more difficult.

For example, IEC has a standard for placing cables into the connector interface. The cable is moved off center, creating tremendous stress on the electrical connection within that connector. If there are air pockets or loose connectors, it will also require tapping on the connector to break conductive particles that may be within an interface free. At Times Microwave, we perform 100% static and dynamic testing on all our RF interconnects. Next, we serialize the interconnects, and keep those tests curves on our website for access at a later time, and we also put that data right on the cables.

Times Microwave Standard Low PIM Portfolio

The Times Microwave standard low PIM cable portfolio includes the SPO™ low-loss, low PIM corrugated copper cable which is a workhorse in terms of low PIM interconnects. We also have a similar product in a fire-retardant version, SPF™. It is a UL listed, type CMR (riser). The durable fire retardant, low smoke polyolefin outer jacket is also suitable for outdoor use. Finally, there is the SPP™ for plenum requirements within a building. This is a UL listed, type CMP (plenum) that meets the standard tunnel test. All three products are available in 250, 375, and 500 sizes in any required connector configuration and length. They are also all 100% tested for static and dynamic PIM, VSWR and insertion loss with a serial marker band that includes test data.

5G and Small Cells Drive New Requirements

5G is driving densification of the network, and small cells are the solution to create this densification. The majority of 5G small cell applications are outdoors—installed around lamp poles, roof tops, telephone poles, etc. One thing that’s pretty common across all of these applications is that they require a lot of RF cable feeds, RF jumpers, jumper cables and feeder cables—in tight spaces. This creates challenging requirements, as the corrugated cables used in many low PIM applications are not the proper cables to make these tight bends.

Times Microwave TFT™ Assemblies

Times Microwave unique TFT™ or TFT™-5G flexible, low PIM, plenum rated jumper cable assemblies use a silver-plated copper flat braid outer conductor construction to create an ultra-flexible cable with a durable FEP outer jacket is suitable for both indoor and outdoor use. The TFT delivers the same VSWR and PIM performance as the helically corrugated SPO, SPS, and SPP in a much more flexible and rugged cable.

The quarter inch UL listed, type CMP (plenum) rated cable is available in 401 (similar to SPO-250 and SPP-250 and 402 versions). The 402 is a smaller diameter cable designed for tight places and smaller runs. TFT assemblies are also available in any required connector configuration and length, as well as 100% tested for static and dynamic PIM, VSWR and insertion loss with a serial marker band that includes test data.

Bundled, Multiport Cable Assemblies

The increasing demand for high coverage MIMO antennas used in 5G applications has led to substantial growth in the number of RF ports. Furthermore, 5G antennas are shrinking in size as higher frequency bands are used to accommodate larger bandwidth requirements, which translates into more antennas in a smaller space. This densification creates numerous challenges related to installation, torquing, ensuring proper weather sealing and more. Small cells are one application that is extremely well suited for a bundled cable solution.

Installation can be a time-consuming, labor-intensive, and logistical nightmare, creating the potential for cables to be the weakest link in the system. 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?

All of these concerns can be addressed by using a bundled cable assembly such as the new TMQ4Ô and TMQ5Ô bundled cable assemblies for 5G. This solution combines industry-standard four and five conductor MQ4/MQ5 connectors with Times Microwave’s high-end coaxial cables to greatly reduce the number of individual connections that must be hooked up while creating a more rugged solution. It checks off all the boxes in terms of antenna port densification, saving a lot of labor with quick and easy fool-proof installation. The entire TMQ4/TMQ5 bundle is sealed to IP-67 specification and features excellent UV resistance, adding to the assembly’s durability for long-term performance.

The most common bundled cable constructions are built with inner cables that are ¼” and smaller. This concept can be used on both non-low PIM and low PIM interconnects. There are a number of other constructions to address low PIM bundled harnesses, including corrugated copper outer sheaths as well as ultra-flexible flat braid constructions.

TMQ4 and TMQ5 also use a spring outer contact so that PIM performance is not tied to the how well the tip of the outer contact is making to its mate. These cluster connectors are keyed with a color code dot on the outer coupling nut to make engagement quick and easy.