Overlapped-MIMO radar waveform design for coexistence with communication systems

This paper explores a collocated overlapped-multiple-input multiple-output (MIMO) antenna architecture and a spectrum sharing algorithm via null space projection (NSP) for radar-communications coexistence. In the overlapped-MIMO architecture, the transmit array of a collocated MIMO radar is partitioned into a number of subarrays that are allowed to overlap. Each of the antenna elements has signals orthogonal to others in the same subarray and to the other subarrays. The proposed architecture not only improves sidelobe suppression to reduce interference to communications system, but also enjoys the advantages of MIMO radar without sacrificing the desirable characteristics such as beampattern and SNR gain. The radar-centric spectrum sharing then projects the radar signal onto the null space of the communications system's interference channel to avoid interference from the radar. Numerical results are presented that show the performance of the proposed design in terms of overall beampattern and sidelobe levels of the radar waveform and finally shows a comparison of the proposed system with existing collocated MIMO radar architectures.