Super-Resolution of Radar and Radio Holography Systems Based on a MIMO Retrodirective Antenna Array

The systems of short-range radiolocation and multistatic radio holography based on multielement MIMO antenna arrays (AAs) with recirculation of orthogonal signals in the spatial feedback circuits of AA transmitting element–​​target–AA receiving element–AA transmitting element are investigated. The generalized ambiguity function in spatial coordinates for an ensemble of coherent orthogonal sounding signals with allowance for the partial propagation constants of the feedback circuits is obtained. The characteristics of the range, azimuth, and elevation resolution in MIMO retrodirective systems are determined based on the analysis of two-dimensional and one-dimensional sections of the generalized ambiguity function (GAF). For the centimeter wavelength range, the GAF cross sections of the azimuth–elevation and range–elevation are compared with and without recirculation as well as at different ranges to the target. The results show the presence of super-resolution effects in MIMO systems with spatial signal recirculation and a nontrivial dependence of the resolution on the target range.