What is Semi-Rigid Coax Cable?

Meet the Connector: Semi-Rigid Coax Cable

This semi-rigid transmission line can be formed as needed and will hold its shape to fit the needs of various applications.

Semi-rigid coax cable is a coaxial transmission line that can be formed to fit the needs and dimensions of a specific application. Custom assemblies can also be made that are preformed to fit easily into specific spaces. This type of cable is used in applications where precision, minimal signal loss, and high-frequency performance are important, such as in telecommunications, radio-frequency (RF) systems, military and aerospace applications, and testing equipment.

The construction of semi-rigid coax cable is simple: It consists of a metal wire conductor, typically copper, centered inside of a dielectric insulating material, and encapsulated inside of a flexible metal tube. This outer tubing material may be made of braided copper or aluminum and reduces electromagnetic interference (EMI) and protects the inner conductor.

SV Microwave builds semi-rigid cable assemblies in-house to the precise dimensions and bend configuration needed.

Semi-rigid cables are electrically stable, especially when compared to flexible coax cable that has a braided wire outer tubing. The properties of the metals and dielectric materials will change in applications that experience temperature fluctuation, so it is important to use phase stable cables for critical systems.

This cable product is available in a wide range of sizes and is compatible with many connectors.

Design Notes

Standardization: Semi-rigid coaxial cable can be specified to meet MIL-Specs.

Winchester Interconnect’s semi-rigid coax cable can be built, custom configured, and tested to meet the MIL-DTL-17 (MIL-C-17) performance requirements.

Forming semi-rigid cable

Forming a semi-rigid cable should be done using specialized tools that bend or form the cable into shape without damaging the wall of the outer tubing. Reforming a cable can result in damage to the outer conductor, affecting the electrical performance of the cable assembly. While aluminum and soft copper can be shaped by hand, tools are recommended to minimize the risk of damage to the coax.

Properties

Semi-rigid cable assemblies typically support RF signal transmissions up to 65 GHz. Higher frequency applications (up to 110 GHz) are possible using a cable terminated with 1.0 mm connectors.

Size: Semi-rigid coax comes in a variety of sizes ranging from 0.020 inches in diameter up to 0.250 inches in diameter.

Impedance: Semi-rigid coaxial cables are usually designed with characteristic impedances of 50 ohms or 75 ohms, with 50 ohms being the most common for RF and microwave applications.

Insertion loss: For a 50-ohm semi-rigid coax cable, the insertion loss is usually in the range of 0.1 to 0.5 dB per meter (at frequencies of 1 GHz to 10 GHz), depending on the specific cable type and its construction. Higher frequencies generally result in higher insertion loss.

Frequency Range: DC to 40 GHz

Dielectric Withstanding Voltage (DWV): Semi-rigid cables typically have a dielectric voltage rating in the range of 500 V to 2000 V, depending on the materials used for the dielectric (such as Teflon or PTFE).

RF Leakage: Shielding effectiveness is often in the range of >90 dB at high frequencies, but this can depend on the shielding design, which could include braided shields, foil, or a combination of both.

Temperature Range: -55 °C to 200 °C

Smiths Interconnect semi-rigid space qualified cables are available with a copper or aluminum jacket, a selection of different platings, and 4 different diameters (.047”, .085”, .141” & .250”).

Markets and Applications

Datacom/Telecom, Test & Measurement, Medical, Military and Aerospace

Suppliers

Molex, Radiall, Rosenberger, Samtec Inc., SV Microwave, Times Microwave

Related products:

Coaxial cable

RF coaxial connectors

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