激光相干雷达中光电双下变频技术  

Optoelectronic dual down-conversion technology in laser coherent radar

作　　者：张奕康 眭晓林[1] 刘波[1] 吴姿妍 梅博 王波 Zhang Yikang;Sui Xiaolin;Liu Bo;Wu Ziyan;Mei Bo;Wang Bo(Science and Technology on Solid-state Laser Laboratory,North China Research Institute of Electro-optics,Beijing 100015,China;Yuchen Optoelectronic Technology Co.,Ltd.,Shanghai 200333,China)

机构地区：[1]华北光电技术研究所固体激光技术重点实验室,北京100015 [2]上海羽宸光电技术有限公司,上海200333

出　　处：《红外与激光工程》2023年第11期69-77,共9页Infrared and Laser Engineering

基　　金：固体激光技术重点实验室基金项目(H202201030942,6142404200105)。

摘　　要：在激光雷达远程测距中,雷达接收机需要在接收信号信噪比较低的背景下,对其中的有用信号进行识别、提取和判决。因此,为保证雷达系统的探测距离和精度,在激光发射功率一定的前提下,需在信号接收处理的各环节中设法提高信号的信噪比。当前外差式激光雷达接收机在变频时将本振光和信号光直接混频,导致镜像频率噪声与有用信号叠加,致使解调信噪比恶化。针对激光雷达接收机提高信号信噪比的需求,提出了一种在信号解调过程中对镜频干扰进行抑制,从而提高解调信噪比的方法。采用光电联合I/Q下变频,首先参考Hartley结构,在光信号的解调过程中对镜频处的噪声进行抵消,随后采用I/Q支路不平衡补偿算法对潜在的双支路不平衡量进行矫正,最后使用数字正交下变频将中频信号解调至基带。仿真和实验表明,该方法能够有效消除调频信号变频过程中引入的镜像频率噪声,相较于传统激光相干雷达接收机方案,该方案解调得到的基带信号信噪比提升了约3 dB。Objective In lidar remote ranging,the lidar receiver needs to extract weak signals from noisy received signals.The detection ability of the lidar receiver for weak signals is an important part of ensuring the detection distance and accuracy of the lidar system.Improving the signal-to-noise ratio(SNR)of the demodulated signal can effectively improve the detection distance and accuracy of lidar.Under the premise of a certain laser transmission power,it is necessary to improve the SNR during the reception process.Traditional heterodyne lidar receivers typically down-convert the lidar echo signal to the baseband through two down-conversions.The first downconversion directly mixes the echo light signal with the local oscillator light,which introduces additional mirror frequency noise.Due to the mirror frequency noise being the same as the useful signal frequency after demodulation,the noise cannot be eliminated through a filter after demodulation,resulting in a deterioration of the SNR of the demodulated signal.In contrast,using orthogonal demodulation can suppress the elimination of mirror frequency noise through the phase relationship between the two branches during the demodulation process,thereby improving the SNR of the demodulated signal.In practical applications,affected by the non-ideal state of the device,the two branches in the quadrature demodulation structure may not be able to achieve a fully balanced state.Therefore,the algorithm compensation for the orthogonality of the two branch signals is also worth in-depth study.The use of appropriate mirror frequency suppression down-conversion structures and the use of relevant algorithms for imbalance compensation is expected to improve the detection performance of lidar systems.Methods Based on the principle of receiving and demodulating echo signals in a lidar system,and referring to structures such as Hartley and Weaver,an orthogonal down-conversion structure for optical signals in the receiver was constructed.At the same time,based on the statistical charact

关 键 词：相干激光雷达 镜频抑制 正交解调 雷达接收机 

分 类 号：TN958.98[电子电信—信号与信息处理]