Generalized Ambiguity Function Properties of Ground-Based Wideband MIMO Imaging Radar

The ability of multiple-input multiple-output (MIMO) radar to provide enhanced performance has been verified in both theoretical and practical level. Through applying orthogonal waveforms, this type of system can realize far more observation channels than the actual number of transmit and receive (T/R) elements. Generally, the azimuth one-dimensional (1-D) generalized ambiguity function (GAF) and resolution of a MIMO radar system are analyzed by pattern theory, which can only analyze the GAF along the equidistant curve to the radar's center. However, the two-dimensional (2-D) GAF of wideband MIMO radar system shows that its sidelobes are not along the equidistant curve accurately due to the coupling effect between the range-dimension and the azimuth one. Obviously, the traditional pattern theory becomes invalid in this case. To tackle this problem, the 2-D GAF and the spatial spectrum of far-field targets are derived in this paper. By analyzing the 2-D GAF, existence of three individual directions of sidelobes is revealed and it is proved that every sidelobes is along a straight line in the pseudopolar coordinate system. Furthermore, a method to calculate the 1-D GAF and resolution in the arbitrary direction is proposed. Finally, a simulation and two experiments have been carried out to validate the theoretic results.