Measured RF characteristics of a TEM-wire fed reflector

The RF characteristics of a parabolic reflector antenna illuminated with a transverse-electromagnetic (TEM)-wire feed are described. The reflector operates in the frequency range of 150 to 3750 MHz (25:1 bandwidth) and has a diameter of 48 in. (0.61 lambda at the lowest operating frequency). The TEM-wire feed is formed by spreading out the wires of a two-wire transmission line. The length of the individual wires was fixed at 20 in. ( approximately lambda /4 at 150 MHz) and the wires were arranged in an exponentially flared configuration. Measured RF characteristics including voltage standing wave ratio (VSWR), gain, directivity, patterns, and axial ratio for an e/sup x/ feed configuration are presented. The VSWR characteristics are cyclic with frequency. The reflector's half-power beamwidth and directivity vs. frequency curves generally have the same slope as a conventional reflector antenna.<>