Retrodirective arrays for wireless communications

This article reports the recent progress in active and passive retrodirective arrays using phase-conjugation techniques. The arrays presented here are designed for wireless communications in microwave bands and have other features in addition to self-phasing aspects such that they can be applied to practical communication systems. The reliance on purely analog circuitry offers system simplicity and high-speed response. The self-beam-steering feature potentially offers the improvement of communication link gain between an interrogator and a retrodirective array, reducing the burden on transmitting and receiving amplifiers. By implementing a receiving function, it has been demonstrated that retrodirective arrays can also be used in bidirectional communications in either a full or semiduplex manner, initiating a new class of transceiver architecture