The Study On The Sidelobe Suppreession Ofliquid Crystal Optical Phased Array Laser Radar

Phased array laser radar is a new type laser radar which use array antenna. Compared with traditional laser radar, phased array lidar has lots of advantanges, such as fast speed, high flexibility. In recent years, liquid crystal optical phased array has been used in the field of laser radar as a core device. However, the problem of sidelobe is inevitable. In the past, density weighted was used as the most common method When solving the issues of sidelobe suppression. But for the liquid crystal optical phased array, the method of density weighted is not appropriate. And, there is no widely recognized method of sidelobe suppression as it comes to the problem of the liquid crystal optical phased array, Therefore, the sidelobe suppression of liquid crystal optical phased array has become more and more important in recent years.In this paper, the author summarizes the development of laser radar of optical phased array both in China and foreign countries, especially the development of array technology and its sidelobe suppression problems. The author introduces the structure, principle of liquid crystal optical phased array and the system of liquid crystal optical phased-array laser radar. Based on Fraunhofer diffraction theory and Fourier optics theory. the author derives wave control principle of liquid crystal optical phased array both in ideal situation and in the situation when Duty cycle is not equal to1. On the basis of the blazed grating modulation idea, adjusts the distribution of the outgoing phase of the liquid crystal optical phased array to achieve sidelobe suppression. When phase delay between the two adjacent phase control unit△φ=2πm/N, we can realize0level of the single-cycle diffraction and the m level of the multi-cycle Coincide. in order to achieve sidelobe suppression. In addition, the author analyzes the influence of edge effect in detail and proposes a non-periodic phase reset method to suppress sidelobe. Finally, different methods have employed, like non-linear non-periodic phase reset, sinusoidal cycle phase reset and random non-periodic phase reset, to suppress sidelobe. and the effect of Non-periodic phase reset method has been analyzed by MATLAB.The research results show that the phase adjustment and non-periodic phase method can effectively achieve sidelobe suppression. This study not only provides a new idea for sidelobe suppression of the liquid crystal optical phased array, but also has a guiding significance in practical application.