Optimization of the TEM feed structure for four-arm reflector impulse radiating antennas

This paper considers the optimization of the feed arm geometry of four-arm crossed-coplanar plate impulse radiating antennas (IRAs) when the angular position and extent of the arms are taken as free parameters. Previously, optimization of this class of antenna considered only the symmetric case where the two pairs of crossed feed arms were perpendicular to each other. Comparison is made using the prompt aperture efficiency, and the results indicate that the efficiency of four-arm IRAs can be increased from /spl sim/25% for the perpendicularly crossed arms to /spl sim/35% for the optimum configuration. In addition to the optimization, the feed impedance of coplanar feeds is presented for general values of feed arm angle and plate width, and the optimum feed impedance is computed for each feed arm angle. The results can be used to design the optimal four-arm IRA with an arbitrary specified input impedance.