A Novel Radar Forward-Looking Three-Dimensional Imaging Algorithm on Moving Platform Based on Vortex Electromagnetic Wave

Vortex electromagnetic waves (VEMW) have unique wavefront phase modulation characteristics. As a new freedom of degree in diversity for radar transmitter, the VEMW radar (VEMWR) can yield radar cross-section (RCS) diversity, improve signal and information processing dimensions and performance. The detection and imaging performance of VEMWR has been verified in various radar systems. This article focuses on the imaging application of forward-looking radar imaging on moving platform, and proposes a multiple-mode scanning method for large imaging field of view based on a uniform circular array (UCA) system. Next, an improved two-dimensional (2D) back-projection and range-doppler algorithm (BP-RD) is proposed, utilizing the difference of magnitude and Doppler frequency at different elevation of multi-mode VEMW and phase difference at different azimuth angles, to achieve 3D imaging of the target. Due to the VEMW 's energy divergence, as the elevation angle increases, the beam pattern gain of the high-mode VEMW decreases sharply. The proposed method can effectively improve the signal processing gain by utilizing the energy distribution of multiple modes in the spatial domain. Based on the imaging results of the point target, it was verified that the normalized gain of target imaging results is basically equivalent either at low or high elevation within the multi-mode VEMW field of view, the algorithm exhibits outstanding stability.