A wide band TEM horn array radiator with a novel microstrip feed

We describe a TEM horn phased array radiator with a novel microstrip feed. Because the field profile in the TEM horn is uniform in amplitude and phase, multiple microstrip feeds can be inserted into a single radiator and their signals combined uniformly by the TEM horn; this particularly attractive feature makes possible low loss, wideband transmit power combining in the radiator rather than in the microwave module. Unlike Vivaldi notch and tapered slot antennas, the TEM horn radiator field configuration resembles that of a rectangular waveguide radiator and should have high cross-polarization rejection. Using a commercially available finite element analysis tool, we have designed in detail a dual-polarized array aperture operating from 1 to 5 GHz using this radiator. The element spacing supports full quadrant scan over the entire band of operation with a predicted scan VSWR less than 3:1 up to 52 degrees in elevation. Our simulation predicts better than 25 dB cross-polarisation rejection in the principal planes.