RF Coaxial Cables are one of the most common transmission line types in use today. Part of the reason for this is that there is a wide range of design freedom and material use that allow for RF coax cables to be designed for a wide range of applications. Moreover, RF Coaxial Cables are predominantly used in the transverse electromagnetic (TEM) mode, with a frequency range that is dedicated by the physical geometry of the inner and outer conductor of the RF cable. The TEM mode is relatively efficient and exhibits predictable performance, as the RF conductor losses and dielectric losses are relatively straightforward to model and measure.
Coax cables are used as part of RF coax cable assemblies when terminated with RF coax connectors, but also on their own when used as jumpers in between transmission lines or RF ports that are crimp or solder attached. Most coax RF cables are either 50 Ohm coaxial cables or 75 Ohm coaxial cables, where the majority of applications use 50 Ohm coax, except for broadcast and other specialized applications using 75 Ohm coax.
RF cables are either flexible coaxial cable, formable coaxial cable, corrugated coaxial cable, or semi-rigid coaxial cable, or rigid coaxial cable. Flexible coaxial cables are one of the most common types, with braided, banded, or taped jackets/outer conductors that allow a high degree of flexibility and flex cycles. Corrugated coax cables can also be flexed to some degree but are generally stiffer and heavier than flexible coax and made for longer runs in conditions where it may be likely that a coax cable could be crushed. Formable coax cables are made with a stiff conductors/jackets that can be hand formed into a given position, but usually only have a limited number of cycles and should only be formed a limited number of times. This cable type is very high performance and can be relied upon to hold the formed shape once bent, which can be advantageous for applications that require consistent performance.
Semi-rigid and formable coaxial RF cables are often confused with each other. The main difference is that semi-rigid coax use is made with a solid conductive outer conductor/jacket and should only be formed once with the appropriate tools. Whereas a formable coaxial cable is typically formed or reformed by hand.
RF coaxial cables are made of various sizes and materials to accommodate different frequency ranges, power handling capabilities, and environmental requirements. Many RF cables are designated with a “RG” number, which is a designation method that rates back to early military specifications for coax. There have been many innovations with coaxial cables, and specialized coaxial cable designs that fill the needs in virtually every application.