A Wavefront Modulation Method with Converged Energy for Radar Forward-looking Imaging

Radar forward-looking imaging technology has significant research and application value. One typical method is to modulate the electromagnetic wavefront to form differential electromagnetic excitation at the target, providing the possibility for target resolution within the beam. However, the existing wavefront modulation imaging methods have the problem of energy divergence, which is unfavorable to the application of radar in long distance and low SNR scenarios. To solve the problem of energy divergence, a wavefront modulation method based on the amplitude modulation of array element excitation is proposed in this paper. This method controls the wavefront phase of the radiation field by changing the excitation amplitude of each element of the array antenna. The wavefront phase of the radiation field shows an approximate linear gradient with the elevation angle, and there is a main-lobe beam with concentrated energy in the propagation direction. In this paper, the generating method of the radiation field is deduced theoretically, and the characteristics of the radiation field are analyzed by simulation. Secondly, the design method of the radiation field is proposed and the limitation of the array size on the characteristics of the radiation field is analyzed. Finally, the imaging model of the radiation field is derived theoretically, and the point target imaging is simulated. Compared with the existing wavefront modulation imaging method, the wavefront phase of the radiation field generated by this method still has a phase gradient, and the radiation field energy is more concentrated. The proposed method can improve the forward-looking imaging ability of the wavefront modulation method under the condition of low SNR, which is of great significance to the development of radar forward-looking imaging technology.