Study On Robust Adaptive Beamforming For MIMO Radar

Multiple-input multiple-output (MIMO) radar is an emerging technology that hasdrawn considerable attention recently. Robust adaptive beamforming is a key issue inMIMO radar. In this thesis, robust adaptive beamforming and robust beampatternsynthesis are studied for monotatic and bistatic MIMO radar. The main contributions ofthis thesis are summarized as follows:1. Robust adaptive beamforming for monostatic MIMO radar is studied. Firstly,the signal model of MIMO radar and two signal processing constructions are given.Then almost all the available methods of robust adaptive beamforming for MIMO radarare shown. We point out the process that robust beamforming for transmitting arraydistortions is cascaded with robust receiving adaptive beamformer, is more fulfiled therequirement of practical systems due to the smaller computational complexity. Toprovide enough robustness to transmitting array distortions, a robust transmittingadaptive beamformer and a robust mismatched filter are proposed.2. A two-side adaptive matrix approach (AMA) is proposed for beampatternsynthesis for MIMO radar. By two-side matrix weighting, the optimization problem ofAMA is converted to a double quadratic problem with two smaller dimension matrixweight. Comparing with AMA, TS-AMA has smaller computational complexity.3. To estimate the DOD and DOA of bistatic MIMO radar when the transmittingand receiving arrays are not perfectly calibrated, a robust Capon beamformer (RCB) isproposed. Using the Kronecker structure of the transmitting-receiving steering vector,the proposed algorithm converts the cost function of RCB to a double quadratic onewith respect to the transmitting and receiving steering vectors. The new optimizationproblem can be efficiently solved by combining bi-iterative algorithm with Lagrangemultiplier methodology. Due to a smaller coefficient can be found in each step of theiterative procedure, the proposed algorithm is more robust and can estimate the powerof the desired target more accurately. When the arrays are perfectly calibrated, the DODand DOA can be estimated from the obtained transmitting and receiving steering vectors,respectively.4. To suppress the concentrated jammers in the presence of unknown mismatchesof the adaptive arrays, a robust beampattern synthesis algorithm with low response in aspecified region is proposed. The proposed algorithm minimizes the worst-case output power while maintaining the response of the robust region distortionless and lowresponse in a specified region, where the concentrated jammers may impinge into thearrays according to some prior information. The proposed algorithm has the form of asemi-definite programming and hence can be efficiently solved by convex optimizationtoolbox. Compared with the available beampattern synthesis algorithms, the proposedalgorithm has better robustness, higher output signal to interference plus noise ratio andmore accurate power estimation.