Orthogonal waveforms design and performance analysis for MIMO sonar

In this paper, a Multiple-Input Multiple-Output (MIMO) sonar system which can deal with multiple targets is discussed, where orthogonal waveforms are transmitted simultaneously. According to the requirement of waveform orthogonality, the orthogonal frequency division pseudo-random signal (OFD-PR), orthogonal frequency division determinant signal (OFD-LFM) and the spread-spectrum code-based signal (Gold-BPSK) are designed. The Maximum Likelihood (ML) DOA estimator and CRB for MIMO sonar is described. The performance of MIMO sonar based on different waveforms is analyzed via experiments in an anechoic water tank. Simulation and experimental results show that the waveforms which we design possess the higher resolution for multiple source DOA estimation than its phased-array and they could resolve the two targets with a separation of 1/2 beam width at low SNR. The analysis of DOA estimates and experimental results show that the OFD-PR signal has much better performance than others.