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Phase-matched cables for phased array antennas

20 September 2019

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Phased array antennas are used in several different terrestrial, oceanic, aeronautic and space applications, such as broadcasting, communications, radar, imaging, guidance, navigation and control. Conventional antennas incorporate gimbals and motor drives that are used for tracking and pointing the antenna in the desired direction. Phased array antennas consist of several smaller antennas that are configured in an array with the correct phase relationships, enabling them to be steered electronically, eliminating the need for high-torque motors and gimbals. Radio waves from the individual antennas in the array can be added together to focus electromagnetic radiation in the desired direction, resulting in high signal strength, long range and wide coverage, while minimizing extraneous noise and interference.

Phased array antennas operate on the principle that superposition (or adding) of two or more radiation sources will amplify each other if the signals are in phase, and will interfere with (or subtract from) each other if the signals are out of phase. In this manner, phased array antennas can greatly amplify radio signals in the desired direction and attenuate the signals in undesired directions. The performance of phased array antennas depends on the ability to control the amplitude and phase of radio signals in each element of the antenna array. The precise control of amplitude and phase ensures the directivity and improves the efficiency of phased array antennas.

Phased-matched cable assemblies

Cable assemblies can account for significant sources of amplitude and phase errors in phased array antennas. For example, two apparently identical coaxial cable assemblies can exhibit different phase characteristics due to slight variations in materials and manufacturing tolerances. In a coaxial cable, the impedance of the cable is a measure of its resistance to electrical current flow, which affects the amplitude and phase of signals passing through the cable. It is essential to control the impedance among the different cable assemblies to ensure the correct phase among the different antenna elements. This is accomplished through the phase-matching process, which carefully controls the inner and outer conductor dimensions and the dielectric materials that separate the two conductors in a coaxial cable.

A dielectric material behaves like an insulator that separates positive and negative charges from one another. The dielectric constant in a cable is determined by the non-conducting plastic, rubber or air that insulates one conductor from the others. A coaxial cable’s dielectric constant determines its characteristic impedance, efficiency, capacitance, cutoff frequency and the velocity of propagation of signals that pass through it. Variations in dielectric constant among different cable assemblies can degrade the performance of a phased array antenna.Figure 1. PIC Wire and Cable can produce a variety of custom coaxial cable solutions. Source: PIC Wire and CableFigure 1. PIC Wire and Cable can produce a variety of custom coaxial cable solutions. Source: PIC Wire and Cable Phase matching of cable assemblies requires the careful screening and control of cable materials and construction techniques to ensure a consistent dielectric constant among the cables.

PIC Wire and Cable

PIC designs, develops and manufactures lightweight, low loss and flexible phased-matched cables and assemblies. By relying on a strong process foundation and up-to-date tools, PIC Wire & Cable manufactures a wide variety of certified cable assemblies, including phase-matched cables. Their highly skilled and trained technicians are capable of producing high-quality, premium cable products and services that are compliant with the most stringent customer and industry requirements, including ISO 9001 and AS9100:D.

More information about PIC Wire and Cable can be found on their website.

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