Retrodirective array for RFID and microwave tracking beacon applications

A novel and compact four‐element retrodirective array (RDA) prototype is realized. It demonstrates excellent performance in terms of retrodirectivity and sensitivity. Each element employs a phase conjugator (a biased FET mixer) with a conversion gain of 5.46 dB. The LO is set at 19.61 GHz and is pumped into the element while the RF operates at 9.8 GHz. The mixer generates an IF signal with a frequency offset of 10 MHz from the RF to separate the transponded signal from the interrogating signal. Retrodirectivity is observed over a wide range of incidence angles from −50° to +50°.