Joint Range and Angle Estimation by FDA-MIMO Radar With Unknown Mutual Coupling

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Frequency diverse array-multiple-input multiple-output (FDA-MIMO) radar is characterized by a range-angle-dependent transmit antenna beampattern, where both range and angle of the target can be jointly estimated. However, the performance of existing estimation algorithms degrades in the presence of mutual coupling effect. To overcome this drawback, this paper deals with the problem of joint range and angle estimation by FDA-MIMO radar with unknown mutual coupling. At the design stage, the mutual coupling matrices (MCM) are constructed in both transmit and receive arrays, exploiting the banded symmetric Toeplitz structure, where the mutual coupling effect is eliminated by transforming the MCM into a diagonal matrix with a selection matrix. Subsequently, the range ambiguity is resolved by setting two linear coprime frequency increments, which locates the true target at the overlap of the peaks corresponding to the two spatial spectra. Furthermore, to reduce the computational cost resulted from the two-dimensional (2-D) grid search, an iterative procedure based on the coordinate descent (CD) algorithm is considered by alternating between the optimization over one variable keeping the other fixed. At the analysis stage, the closed-form solutions of the mutual coupling coefficients are given by utilizing the estimated range and angle. Moreover, a comparison in terms of estimation performance in different coupling scenarios is carried out, where the Cramér-Rao lower bound is provided as the benchmark. Numerical results verify the effectiveness of the considered estimation strategy in multiple simulated scenarios.