Waveform design for detection in MIMO over-the-horizon radar

Waveform design is studied for a multiple-input multiple-output over-the horizon (MIMO-OTH) radar system faced with a combination of additive Gaussian noise and signal dependent clutter. We define the waveform transmitted at each antenna as a weighted sum of a set of orthogonal sequences. Assume that different transmit antennas use the same set of orthogonal sequences, while the weighting factors can be different which allows the transmitted waveforms from different antennas to be either orthogonal or nonorthogonal. Optimum waveforms are designed to maximize the target detection performance of the MIMO-OTH radar system when the other parameters are fixed. The constraint of fixed total transmitted energy is considered. We show that the waveform optimization problem can be reduced to the optimum selection of the weighting factors. In the studied examples, the optimum waveforms are nonorthogonal rather than orthogonal. We show that the waveforms designed using the proposed approach have detection performance superior to the waveforms usually employed in traditional OTH radar systems. The energy allocated to each of the transmit antennas due to the use of the designed optimized waveform is also analyzed.