Photonics-Based MIMO Radar With Broadband Digital Coincidence Imaging

Photonics-based radars with a large operation bandwidth enable a high-range resolution. Achieving high angular resolution typically demands a large aperture size or a large antenna array, causing increased system complexity, volume, and cost. In this article, we propose a photonics-based multiple-input and multiple-output (MIMO) radar that employs a broadband digital coincidence imaging (DCI) method to achieve super-resolution radar imaging. In the proposed radar system, period one (P1) laser dynamics is used to generate broadband linear frequency modulation (LFM) signals, and photonic frequency mixing is adopted to implement de-chirp processing. To improve the angular resolution, the proposed DCI method implements random phase modulation and multichannel accumulation to the photonic de-chirped signals in the digital domain, obtaining radar observation samples with rich spatiotemporal diversity. Based on the spatiotemporally incoherent observation process, an imaging equation is constructed and solved by a sparse reconstruction method, resulting in the final high-resolution radar image. A photonics-based
$8\times 8$
MIMO radar with a bandwidth of 8 GHz (18–26 GHz) is established. Applying the proposed DCI method, super-resolution 3-D imaging is successfully demonstrated, attaining a range resolution of 2 cm, an azimuth resolution of 0.3°, and an elevation resolution of 0.3°. The experimental results can soundly verify that the proposed photonics-based MIMO radar provides a promising solution to high-resolution forward-looking radar imaging.