An HF-Band Linear Retrodirective Array With Scale Model RCS Measurements

Design of an ultrawideband co-polarized linear retrodirective array (RDA) operating in the high-frequency (HF) band (2–30 MHz) and beyond is reported for the first time and validated using scale model measurements showing good agreement with theoretical and computational models over a 15:1 bandwidth. The vertically polarized simultaneous transmit and receive (STAR) aperture is composed of combined transverse electromagnetic (TEM) horn-loop antenna elements resistively loaded to ensure good match and directional patterns when electrically small. Each antenna element fits within a 3-m radius minimum sphere and 5-m array spacing and is suitable for use with the HF modes of propagation. Monostatic and bistatic retrodirective beamforming networks (BFNs) with and without active enhancement are explored. Experimental validation is accomplished through measurements of a fabricated 1:100 scale model. The radar cross section (RCS) is measured using a low-cost, custom test system where the array is installed in a 3.66 m
$\times 1.22$
m aluminum ground plane. Excellent agreement with the theory showcases the robustness of the proposed RDA and utility of the developed research and development approach.