Antenna Array and Waveform Design for 4-D-Imaging mmWave MIMO Radar Sensors

4D-Imaging mmWave multiple-input-multiple-output (MIMO) radars have significant advantages over conventional radar sensors. However, the physical placement of transmit and receive antennas to achieve the desired virtual array, while considering cost and efficiency is not intuitive. Furthermore, due to the large number of transmit elements in such systems, they necessitate an appropriate strategy for transmit waveforms design. These waveforms should be separable on the receive side while also having low auto-correlation sidelobes. In this paper, we propose a general optimization framework based on Coordinate Descent (CD), to solve the problems of antenna array and waveform design for 4D-imaging radars. First, we propose the CD approach for an optimal array configuration design to obtain a sequence of optimal antenna placements. The objective function converges to a solution that guarantees the desired number of transmit and receive antennas, while the obtained virtual array is as close to the desired one as possible. We, then, propose an entry-based optimization framework based on CD, to jointly design a phase-modulated waveform set optimized based on weighted integrated sidelobe level and spectrum shaping, considering the radar operates adjacent to communication systems. Finally, the simulation results are provided to assess the validity of our proposed methods for both array and waveform design. The former is validated by simulating the virtual array of several commercially available 4D-Imaging radar products. The latter demonstrates that our proposed waveform design can outperform conventional MIMOFMCW approaches, by performing comparative simulations. Finally we show that it can also provide compatibility with other communication systems.