Full-Duplex Wideband Digital Array With Beamforming and Application to Sum/Difference Pattern Retrodirectivity

A fully digital antenna array is developed and experimentally tested for beamforming, null generation, and in-band full duplex (IBFD) retrodirective beam-steering. The supporting S-band array is compact and comprises co-located transmit and receive stacked patch elements with isolation values of 40 dB. In addition, each element is fed using H-shaped slots and dual-differential integrated couplers and this offers dual-polarized operation as required, while a synchronized software-defined radio (SDR) transceiver network was programmed to apply the needed complex weights and phase conjugation at baseband. Moreover, the system shows proof-of-concept by forming sum and difference patterns and also demonstrates self-steering due to an interrogating signal from the far-field. Results show that the digital retrodirective antenna array (RDA) system can achieve a competitive −5-dB monostatic angular scan range of ±47°, needs no frequency offset to operate, and, offers a 6% matching impedance bandwidth (BW). These wideband features make the RDA capable of common, or reconfigurable, carrier offsets for the incoming and re-radiated beams, and this has also been experimentally demonstrated. To the best knowledge of the authors, no similar digital IBFD antenna, RDA system has been designed, programmed, and tested.