This catalog lists the most common configurations for each cable type. If necessary, IW can modify existing designs or design a custom connector to meet your specific requirements. Our standard connectors meet the environmental specifications of MIL-PRF-39012. See table on page 34 for maximum operating frequency.
Determination of Phase Change Over Temperature
The following example illustrates how to calculate the change in phase (and the tracking error) of cable assemblies over a specific temperature range. In this example, the cable is IW 2801, and the temperature range is -40˚C to +80˚C.
* determined by the charts above ** tracking error of two or more assemblies of the same type
Phase Change with Flexing
Phase change when flexing will be slightly different depending on the particular cable. Larger cables have more dielectric and greater internal forces, thus phase change will be greater for cables with larger diameters. When wrapped 360˚ around a 4 inch diameter mandrel, the phase change will be:
+0.30˚ • f – for cables 480, 280, 230, 180 and 170
+0.20˚ • f – for cables 157, 150 and 140
1. Calculate electrical length 2. Calculate change in phase 3. Calculate tracking error
Frequency = 10 GHz f Assembly length = 72 in L Start temp = 20˚C T Dielectric const = 1.4 e Change in PPM = -500* PPM PPM tracking error = ±100 PPM tracking Electrical length = TBD F Change in phase = TBD DF Tracking error = TBD** F tracking
Phase Match & Time Delay
For applications where phase or electrical length is a critical performance parameter, IW can provide matched assembly sets, tested to customer specifications, typically up to 40 GHz, with both Low Loss Phase Stable and Re-Flex™ cable types. Relative phase matching is a common requirement achieved with multiple assembly sets. Typical phase matching tolerances are shown in Table 1 below.
Tighter tolerances may be achievable; IW engineers review all matching requirements on a case by case basis. In addition, IW also provides time delay matched assemblies with tolerances in the order of 2pS being achievable with both Low Loss and Re-Flex™ cable types, and individual assemblies can also be supplied trimmed to a specific electrical length. All matched assemblies are tested 100% for insertion loss and VSWR performance parameters in addition to phase.
Engineering Design Data
TUF-FLEX™ Cable Performance
The same cable was tested to measure performance with successively tighter bend radii. The serving used to create the armor not only provides excellent crush resistance, but maintains the concentricity of the cable as it is flexed through a radius, enabling RF performance to be maintained.
The following contains a list of precautions and procedures that should be taken when handling or installing Insulated Wire cable assemblies. They should be used as guidelines and followed whenever possible. By doing this you can ensure a long assembly life which requires virtually no maintenance.
Handle cable with care:
IW cable assemblies are designed to operate at the highest electrical performance level. High performance cables such as these require special handling procedures to ensure optimum electrical performance. Many of these handling procedures are outlined in detail, however taking just a few basic preventative measures during handling can significantly extend the life of the assembly. You should always take care to prevent anything from being placed on an assembly. This could result in internal damage caused by compression. Also, prevent the cable from bending below it’s minimum bend radius as this will cause the cable to kink, which results in internal damage and subsequent degradation in RF performance.
Limit bend radius whenever possible:
Although IW cable assemblies can accommodate a very small bend radius, it is recommended to use the widest possible radius to fit the application. This will help to keep mechanical stresses low through the bend and prolong the life of the assembly.
Avoid torquing down connector ends until both connectors are mated in position:
It is important to first hand tighten both connectors into position before any torque is applied. If a connector is torqued down before the assembly is routed into position, excessive torsion could be applied at the torqued connector’s termination during the routing. These torsion forces could cause the dielectric to change its mechanical position at the connector termination. This could ultimately lead to an electrical failure.
Avoid twisting assembly to orient connectors:
When installing assemblies with right angle connectors, do not twist the cable or connectors to orient with the mating connectors. Twisting the assembly could result in mechanically changing the dielectric position at the termination and ultimately lead to an electrical failure. Assemblies should be purchased with a specific connector offset angle to match the proper mating connector. If an offset angle needs to be changed during assembly installation, proper adjustment procedures can be obtained by calling IW’s Technical Support.
Avoid bending the assembly at the connector termination:
A cable assembly should never be bent at the back of the connector. Applying a bend prematurely at the end of an assembly and allowing the bend to encompass the connector could lead to the build up of excessive cable forces against the connector and through the bend area. The applied forces will cause the cable to kink. Electrical degradation and possible failure may result.
Avoid pulling an assembly through channeling by the connector end:
Never pull an assembly by its connector when routing it through a structure, channeling or building. Doing this could mechanically damage the connector termination. The assembly should always be pulled by the cable itself. Furthermore, the installation should be assisted by pushing the assembly through the channeling while the cable is pulled. Additionally, it is less stressful to the assembly if it is installed in phases (through individual sections) rather than a single run across the entire routing length.
Never allow an assembly to support its own weight when routed in a vertical installation:
Never allow an assembly to hang freely by its own weight. Clamp down the cable at equal intervals along its length. Cable hangers can be used when it is not possible to clamp down the assembly in a vertical installation provided the assembly has been reinforced for such an installation. Using multiple hangers whenever possible is also recommended to help evenly distribute the assembly’s weight along the run.
Avoid the use of cable ties:
Most high performance cables use an air filled dielectric core. This makes the cable very soft. Therefore any compressive load applied to the cable has the potential of collapsing the dielectric core within the cable. Cable ties and tie wraps are not recommended for this reason. They offer virtually no load distribution and consequently focus very high compressive forces through the tied down area. A concentrated force such as this almost always deforms the cable and significantly degrades assembly performance. For best holding results with minimal clamping forces, IW recommends rubberized clamps. Be sure to select a clamp that will apply a minimum amount of compression force while still offering the desired holding strength. Selecting a clamp that it too small can do as much damage to an assembly as a cable tie.
Avoid subjecting the connector ends to cable axial loads:
Cable assembly life can be increased by clamping down the cable a few inches from the connector ends in applications where the cable will be moving (such as a moving antenna) or where a high vibration condition exists. Clamping the cable down at the cable ends reduces mechanical loads applied to the connector when the cable is moved.
Always wrap connectors in weather proofing when installing outside:
All cable connections that will be subjected to rain and snow should be wrapped in a weather proofing material. A self fusing silicone tape is recommend to create a weather tight seal over the connection. If weather precautions are not taken, water will eventually work its way into the connector assembly causing high insertion losses.
Always provide adequate drip loops:
Always allow for a drip loop in outside applications to prevent water from flowing down the cable and onto the connector. Over time the water could work its way into the connector assembly causing high insertion losses.
Take extra care on short assemblies:
- Always bend assemblies around mandrels whenever possible.
- The use of mandrels or wheels will help to evenly distribute bending loads applied to the cable. This is the preferred method for bending cables.
- Take caution when bending cables by hand.
- Sometimes bending a cable by hand is the only option. In this case the following method should be used:
- Start at bending point keeping hands close together.
- Bend the cable a little at a time working in an outward direction along the bend.
- Return to the center point of the bend and work in an outward direction making the bend a little tighter.
- Continue to return to the center of the bend, and working outward until the desired bend is reached.
Take caution bending cables under 12” in length.
An assembly that is 12” in length and smaller can be very rigid depending on the cable type. The cable becomes rigid because its inner and outer conductors are fully (mechanically) terminated to the cable connectors. The cable is terminated this way to yield maximum electrical performance. Unfortunately, it minimizes the bending characteristics of the assembly because the cable is too short to accommodate the total material volume displacement needed for a typical bend. Often, the minimum bend radius can not be achieved without damaging the assembly. Therefore, short cables should only be used in applications where slight jogging bends will be used. A longer assembly that uses a service loop should be considered as a replacement for a short cable in situation where a tight or sharp bend is needed.
Phase Stable Cable
IW is pleased to announce that it has developed a new line of coaxial cables and assemblies which has improved the performance characteristics for all types of microwave applications. This new line of cable and assemblies yields smaller diameters, lighter weights, lower insertion loss, and enhanced electrical stability versus temperature and flexure. This adds up to the “Best of all worlds” for an engineer designing high performance systems.
Low Loss, Phase Stable Cable
In it’s continuing effort to supply the microwave industry with the highest possible performance, Insulated Wire, Inc., is pleased to announce that it has developed a new line of coaxial cables and assemblies, which has improved the performance characteristics for all type of microwave applications. This new line of cable and assemblies yields smaller diameters, lighter weights, lower insertion loss and enhanced electrical stability versus flexure and temperature. This all adds up to the “Best of all Worlds” for an engineer designing high performance systems. We believe it is imperative that our customer gets the maximum performance, from the widest possible range of products, delivered on time, for the lowest cost.
This new cable line incorporates significant design changes resulting in improved performance. These cables meet or exceed all the material requirements outlined in the MIL-C-17 specification and utilizes silver plated copper conductors, with a very low loss, expanded PTFE dielectric. The outer conductor consists of pure silver, applied in a new proprietary manner that yields lower contact resistance, thus decreasing insertion loss. This new cable line also incorporates a secondary, silver plated, copper braided shield that contributes to excellent RF leakage characteristics, specified at > -100 dB to 18 GHz. The standard outside jacket is a tough, resin melt, extruded FEP, however, PFA, Polyurethane, Tefzel™ and PEEK can be used, depending on the application requirements. IW will also offer an internal ruggedization for cable assemblies, or external armor to provide further mechanical or environmental protection. The internal ruggedization offers enhanced crush resistance and a tighter bend radius. This design offers a more compact package than does the external armor, keeping the size and the weight of the cable assembly down. These assemblies include tough, stainless steel connector bodies. The patented connector designs yield proven performance in the field, on programs, such as, Phalanx, HDR, Cobra Gemini and 767 AWACS.
The 1801 series cable measures .180″ in diameter and typically measures 0.33 dB per foot, at 18 GHz. This is a vast improvement when compared to other available cables on the market, as well as, IW’s previous cable, which measured 0.37 dB per foot, at 18 GHz and measured .230″ in particularly well suited to airborne and satellite applications. The lower insertion loss over long runs of cable allows for less power to be applied, which has the potential to eliminate expensive amplification systems. This new design also yields improved VSWR performance. The typical 1801, (4) four-foot long cable assembly with SMA connectors has a 1.20:1 VSWR to 18 GHz; the 1501 series cable assembly of the same length with 2.9mm connectors has a typical VSWR of 1.25:1 or better to 40 GHz.
The 1401 operating to 50 GHz and the 1501 to 40 GHz make excellent test cables. The very low VSWR and overall electrical stability when flexed, make this cable assembly an inexpensive alternative to the expensive ANA cables. These cables can be ruggedized to withstand production test environments as well as, harsh thermal environments from -65 to +200 degrees Celsius. These cables will withstand repeated flexure and remain within very tight electrical specifications. The 1501 cable data shown for phase stability versus flexure indicate less than a 5 degree change in electrical length at 40 GHz, when the cable is flexed into a tight, 3″ diameter coil. The insertion loss or amplitude stability is also excellent at < 0. 1 dB through 40 GHz.
The excellent stability and high power handling capability makes these cables very good choices for phased array antenna systems. It is extremely important that interconnection cables remain electrically stable during the installation of these sensitive systems. When necessary, IW will phase match assemblies to system requirements. The new cable design allows multiple bends to be put into these matched cables, without significant changes to the electrical length, in addition, this design is very amplitude stable. These cable assemblies typically change < 0.1 dB, at their maximum frequency with the cable bent to the minimum bend radius. The cables are all very flexible and can endure thousands of flexures and remain within the stated electrical specifications set forth.
The low loss nature of these cables allows for higher power levels to be used. This cable technology is being used to help save lives within the field of cardiac medicine. IW is currently supplying a cable used in a microwave ablasion catheter, used to address cardiac rhythm irregularities. The system uses microwave energy to destroy tissue buildup that can cause electrical disturbances and cardiac arrhythmia. IW was selected for this important system because it could offer the smallest diameter cable and worked with the engineers and doctors directly in the development of this cable to achieve the lowest loss, to allow for the greatest amount of power to be applied and keep the catheter within normal body temperatures. As with any of it’s customers, IW goes the “extra mile” to help make a system work properly.
This line of cables is also extremely phase stable when exposed to changes in temperature. It is critical that matched cables change electrically within as small a tolerance window as possible and track in a similar fashion from one cable to the next to maintain proper overall system performance. The change in electrical length must be predictable and consistent. Shown in the graph is a comparison to semi-rigid cable that reflects the improvement that this new design shows over those cable assemblies utilizing solid, PTFE dielectric. The expanded PTFE dielectric material has a nominal velocity of propagation of 84%, making it less reactive to thermal changes when compared to solid PTFE core. The phase profile for this design is very flat and within 600 PPM over a -50 to +120 degree Celsius. This puts this cable among the most phase stable assemblies available from any manufacturer.
The whole line of cables, gives the user great overall flexibility when designing systems. The part number corresponds to the diameter of the cable; an example is the 2401 is actually .240″. These are standard sizes, but IW can manufacture a wide variety of coax cables using this new design to specific customer requirements. IW also offers cables with a 75-ohm impedance that utilizes this new design technique in varied diameters depending on insertion loss requirements.
IW manufactures the broadest line of coaxial cable assemblies available from any company in the microwave industry. Our Microwave Products Division will work closely with its customers, to provide “On-Site” assistance, supporting the successful completion of any interconnection project. IW offers custom, multiconductor cable and assemblies for use, in a wide variety of applications. A complete range of wire and cable products are available including low cost, high performance alternatives to RG cable types. These on-going efforts make IW the industry leader in microwave interconnection technology.
IW supplies internal ruggedization, designated by replacing the ‘1’ in the part number with a ‘3’. This internal ruggedization is available only on cable assemblies. Example: 1801 becomes 1803
Reproduced from the Microwave Product Digest
Phase Change With Flexing:
Phase change when flexing will be slightly different depending on the particular cable. Larger cables have more dieletric and greater internal forces, thus the phase change of larger cables will be greater than smaller diameter cables. When wrapped 360° around a 4 inch cable diameter mandrel, the phase change will be:
Cables 4806, 2301, and 1801: Phase change = ± 0.30*F.
Cables 1501 and 1401: Phase change =± 0.15*F.
F is the frequency in GHz and phase change is in degrees