MIMO Radar Signal Parameter Estimation AndSystem Design

The desire for performance improvement, angle estimation accuracy andincrease in number of targets that can be detected coupled with advances in waveform generation technology and processing power, has motivated the increase in research work on Multiple Input Multiple Output (MIMO) radar systems. MIMO radar achieves more accurate direction estimation by extracting and making use of the phase delay information between each transmitting and receiving antenna pair. This is accomplished by transmitting simultaneously, a set of orthogonal waveforms that can be chosen freely via its antennas. Orthogonality is achieved by phase coding from pulse to pulse and the transmitter can have a range of choice for the transmitted waveform on a pulse-to-pulse or antenna-to-antenna basis. This choice of a multiplicity of transmitted waveforms and of adaptively adjusting them gives MIMO superior capabilities over phased arrays. At the receiver, a bank of matched filters is used to extract the orthogonal components from the echo of each receiving antenna element, where each orthogonal component corresponds to the target’s reflection to each emitted waveform.With the subsequent enlargement in array aperture, angle estimation accuracy and resolution is increased. The number of targets that can be resolved in range and angle is also increased. These advantages come at some cost. For Angle estimation algorithms, the computational requirements are directly affected by the dimension of the collected data. Increase in array aperture due to the virtual arrays also increases sidelobe levels. In bistatic MIMO, the arrays are spaced far away from each other and the Direction-Of-Departure (DOD) and Direction-Of-Arrival (DOA) are different. Spatial synchronization in angle becomes a problem. In conventional bistatic radar, DOD/DOA synchronization is achieved by the transmitting beam and the receiving beam illuminating the target simultaneously. Subspace techniques are known for their ability to reduce the degrees of freedom. High resolution subspace DOA algorithms operate on a reduced parameter space by decomposing the observed signal covariance matrix into two orthogonal spaces, the signal and noise subspaces and estimates the DOAs from one of these spaces. In this research work, firstly we evaluate and compare the performance of some of the traditional subspace based angle estimation algorithms applied to the bistatic MIMO radar scenario via simulationsSecondly; we develop an angle estimation algorithm for a bistatic MIMO radar system based on Unitary Esprit techniques. The algorithm exploits the dual Vandermonde structure and centrosymmetry of the bistatic MIMO radar array manifold, to provide real valued computations and automatically paired Directions Of Departures (DOD) and Directions Of Arrival (DOA) estimates. Simulations are performed to verify the performance of the proposed algorithm. Waveforms based on Binary phase coded sequences (BPSK) and polyphase codes, which are noncircular signals, are encountered in radar, but their noncircularity properties are not exploited for angle estimation purposes. They are only used for pulse compression to increase range resolution. In radio communication, the noncircularity of BPSK signals are exploited for bandwidth expansion and to transmit information to multiuser environments. In our third contribution, we exploit the noncircularity property of non circular signals to construct an augmented conjugate symmetric data matrix from the received data vectors by using both the positive definite hermitian covariance matrix and the elliptic covariance matrix. The algorithm developed, uses real computations based on Unitary ESPRIT techniques to achieve a more improved and automatically paired angle estimates for a bistatic MIMO radar system. Simulations are performed to evaluate the performance of the algorithm.Finally, we design a bistatic MIMO radar system including the transmitted signals which are binary orthogonal waveforms designed from the hadamard matrix using the simulated annealing optimization algorithm. We develop an antenna placement scheme for the bistatic MIMO system and simulate the angle estimation algorithms developed. Simulation results show the effectiveness and performance of the overall design...