Towards High-Resolution Imaging With Photonics-Based Time Division Multiplexing MIMO Radar

A photonics-based time division multiplexing (TDM) multiple-input and multiple-output (MIMO) radar is proposed to realize high-resolution imaging. In this MIMO radar, multiple transmitters generate time-domain orthogonal linearly frequency modulated (LFM) signals based on microwave photonic frequency octupling and optical TDM technique, and multiple receivers implement dechirping of the multi-channel radar echoes based on microwave photonic frequency mixing. The microwave photonic techniques make the system capable to generate and process broadband radar signals, and the TDM yields a high spectral efficiency, which allows a large bandwidth in each transmitter and receiver. Meanwhile, the TDM-MIMO ensures complete orthogonality between different channels and enables good flexibility in arranging more transmit and receive channels. Therefore, the proposed photonics-based TDM-MIMO radar can achieve both high range resolution and high angular resolution. In the experiment, a photonics-based 4 × 8 TDM-MIMO radar is established which has an operation bandwidth of 8 GHz in each transmit channel. The range resolution and angular resolution are estimated to be 1.9 cm and 1.1°, respectively. A broadband back projection (BP) imaging algorithm with both frequency and time-delay dependent phase compensation is proposed, based on which high resolution imaging of single and complex targets is achieved.