Wideband Circular Retrodirective Array With RCS Enhancement

Circular phase mode theory is utilized to analyze, design, and demonstrate an improved performance circular retrodirective array (RDA) over a wide bandwidth. The benefits over existing architectures include the significantly improved isolation between transmit (Tx) and receive (Rx) channels, thus allowing for greater amplification of the retrodirected signal. Theoretical, computational, and experimental results are provided. Theoretical studies examine the proposed beamforming network (BFN) with ideal omnidirectional, bidirectional, and unidirectional element patterns compared to approaches in the open literature. The computational analysis uses a circular array of wideband elements designed for operation in the extended high-frequency (HF) band. For eight elements and an array radius of 9.8 m, retrodirective performance is expected and observed between 10 and 20 MHz. The experimental results are performed with a 1:100 scale model on a custom radar cross section (RCS) measurement table. Measurements and results derived from the tests show good agreement with computations. The importance of active enhancement capability in mitigating the impacts of the residual component of the scattering is demonstrated as well.