Millimeter-wave Radar and mini-SAR Imaging

I. Automotive Millimeter-wave 4D Point Cloud Imaging

The emerging high-resolution four-dimensional imaging radar (4D radar), as the main competitive product of the next-generation 77G automotive millimeter wave radar, can provide high-quality 4D point clouds in the range, azimuth, elevation, and time dimensions.

To advance automotive millimeter wave 4D point cloud imaging technology, we have investigated the orthogonal waveform design [1] for MIMO radar and proposed an innovative time-division multiplexing & and Doppler-division multiplexing MIMO (TDM-DDM-MIMO) framework. Moreover, an attractive complex-valued deep convolutional network (CV-DCN) of super-resolution direction-of-arrival (DOA) estimation is proposed only using single-frame data [2].

Fig. 1. The orthogonal waveform design for MIMO radar

Fig. 2. The workflow of point cloud imaging with deep learning

Fig. 3. The representative work of automotive millimeter-wave 4D point cloud imaging

Related Publications

[1] Mengjie Jiang, Gang Xu*; Hao Pei, Zeyun Feng, Shuai Ma, Hui Zhang, Wei Hong, "4D High-Resolution Imagery of Point Clouds for Automotive mmWave Radar," IEEE Transactions on Intelligent Transportation Systems, doi: 10.1109/TITS.2023.3258688.

[2] Mengjie Jiang, Gang Xu*, Hao Pei, Hui Zhang and Kunpeg Guo, "High-resolution Automotive Radar Point Cloud Imaging and Processing," 2022 Photonics & Electromagnetics Research Symposium (PIERS), Hangzhou, China, 2022, pp. 624-632, doi: 10.1109/PIERS55526.2022.9792662.

II. Automotive Mini-SAR Imaging

Within the field of automotive radar imaging, millimeter wave radar has been widely applied due to its recognized advantages of small-size, low-cost, all-weather working, high-resolution in range, and etc. Compared with the array imaging technique, synthetic aperture radar (SAR) takes advantage of high resolution, and can achieve a clearer outline of the scene.

We have investigated the automotive mini-SAR imaging technology. A high-resolution MIMO SAR imaging algorithm is proposed in the framework of Doppler-division multiplexing (DDM), where a novel multi-channel back-projection (BP) approach is presented for coherent multi-channel image integration [1], which can effectively achieve the near-field and wide-angle focusing imaging. To be specific, digital beamforming (DBF) and beampattern synthesis based on the alternating direction method of multipliers (ADMM) is used for multi-channel SAR image coherent fusion, which can achieve focused imaging for the interested region.

Fig.1. The flowchart of the proposed DDM-MIMO SAR algorithm.

Fig. 2. SAR images of region of interest using multiple apertures fusion in a spotlight-like mode (bottom). MIMO SAR imaging result of a parking lot using BP algorithm (Top).

Related Publications

[1] Bangjie Zhang, Gang Xu*, Rui Zhou, Hui Zhang and Wei Hong, "Multi-Channel Back-Projection Algorithm for mmWave Automotive MIMO SAR Imaging With Doppler-Division Multiplexing," IEEE Journal of Selected Topics in Signal Processing, vol. 17, no. 2, pp. 445-457, March 2023, doi: 10.1109/JSTSP.2022.3207902.

III. Airborne Mini-SAR Imaging

For highly squinted SAR imaging, the airborne SAR is very sensitive to atmospheric turbulence that causes serious trajectory deviations.

We have investigated the airborne mini-SAR imaging technology. A robust autofocusing approach for highly squinted airborne mini-SAR imagery using the extended wavenumber algorithm is proposed, which is capable of estimating the range-dependent phase errors [1].

Fig. 1. Processed images. (a) Using the modified SPGA MOCO. (b) Using the proposed MOCO approach. (c) Zoom of (a). (d) Zoom of (b).

Related Publications

[1] Gang Xu, Mengdao Xing, Lei Zhang and Zheng Bao, "Robust Autofocusing Approach for Highly Squinted SAR Imagery Using the Extended Wavenumber Algorithm," IEEE Transactions on Geoscience and Remote Sensing, vol. 51, no. 10, pp. 5031-5046, Oct. 2013, doi: 10.1109/TGRS.2013.2276112.