Interleaved Retrodirective Sub-Arrays for Null-Steering Interference Rejection

Retrodirective arrays have been established as a unique type of high-speed, self-steering array with the flexibility to integrate with a wide range of communication functions. However, their automatic phase reversal function prohibits the use of channel weighting prior to retransmission, greatly limiting its beamforming capabilities. In this work, an interleaved sub-array architecture is proposed to introduce a null-steering feature into retrodirective arrays for interference rejection. The system maintains its simple high-speed operation with a Butler matrix receiver rather than a digital receiver. A minimum number of phase shifters are required for null-steering. An 8-element prototype is fabricated to demonstrate this new feature. Measured pattern results validate the effectiveness of the introduced null-steering capability.