A Sparse Array for 77 GHz 4D High-Resolution Imaging Radar Based on Entropy Model and Convex Optimization

Modern urbanization traffic monitoring systems with ever-complex load scenarios put forward strong demand for the 4D high-resolution imaging radar in all weather conditions. A narrow beam is an important foundation for realizing high-resolution images in the azimuth plane. In this paper, a sparse array for 77 GHz 4D high-resolution imaging radar based on the entropy model and convex optimization is presented, which can generate a narrow beam scanning in a large range without grating lobes. An example of a 16-element array is presented to demonstrate the effectiveness of the proposed method. Compared to the half-wavelength array with 16 identical elements, i.e., 8λ0, the proposed sparse array with the same element number can enlarge the aperture to 14.7λ0. As a result, the beamwidth of the sparse array is narrowed by 1.61° (25.6%), 1.89° (26.2%), 4.8° (45.2%), in the 0°, 30°, and 45° respectively. Moreover, the sidelobe level of the proposed sparse array is lower than -8 dB when scanning to ±45°. Additionally, the gain flatness is 1.5 dB in the whole scanning range.