The split reflector technique for broad-band impedance matching of center-fed antennas without pattern deterioration

The problem of matching the impedance of a center fed reflector over a wide frequency band without pattern deterioration has been attacked in a variety of ways. In this paper a new method is described which has produced excellent results in a single-layer pillbox. Measurements of a voltage standing wave ratio not exceeding 1.35 over a 12% frequency band plus minor lobe discrimination of 18 db are reported. The technique employed involves a split pillbox fed by a waveguide hybrid. The reflections from the symmetrical reflecting structure are substantially all absorbed in a load. Aperture phase correction is accomplished by an acceleration or a dielectric section and results are described. The boresight shift is demonstrated to be a small fraction of beam width. Discussion of the application of this technique to paraboloidal reflectors is included.