A two-dimensional retrodirective array using slot ring FET mixers

A printed 4-by-4 retrodirective antenna array has been developed, which employs the heterodyne phasing technique at 6 GHz. Each array element comprises a balanced FET resistive mixer, integrated in a ring slot which serves as both an antenna and hybrid. Driven by a reference signal at twice the incident frequency, the mixers receive and reradiate incident signals while imparting a conjugate phase shift onto them. The result is retrodirective radiation that is not critically dependent on either the array geometry or the planarity of the wavefront. This makes conformal retrodirective arrays possible. The backscatter pattern of the array exhibits a wide-angle response (>100 degree scan range) in both planes.