光载微波信号抗大气干扰的研究

Study on anti-atmospheric turbulence interference of light borne microwave signal

为了研究射频强度调制激光信号光源的参量,特别是调制深度对调制波的抗干扰能力产生的影响,采用干涉法对射频强度调制激光信号在通过大气湍流干扰后其相位的变化进行了理论分析和实验验证。搭建了Mach-Zehnder干涉仪,参加干涉的两束光分别为未经调制的单频光和调制后的双频光。以干涉条纹对比度作为信号相位起伏的衡量标准,比较不同大气湍流干扰条件下,干涉条纹的对比度随调制深度的变化。大气湍流由空间光调制器模拟产生,分别在26.32%,42.04%,67.59%和85.04%4种调制深度下,比较有无大气湍流时干涉条纹的对比度的变化。结果表明,调制信号的调制度越深,其抗大气湍流干扰的能力越强。该结论对双频激光雷达光源的选择具有一定的参考意义。

In order to study effect of parameters of radio frequency （ RF） intensity modulation laser signal sources,especially modulation index, on anti-atmospheric turbulence interference, phase change of the RF intensity modulation lasersignal passing through atmospheric turbulence was analyzed theoretically and verified experimentally. A Mach-Zehnderinterferometer was built, and two interference beams were single frequency light without modulation and dual frequency light withmodulation respectively. The contrast of interference fringes was taken as the criterion of signal phase fluctuation. The contrast of interference fringes with the change of modulation depth were compared under different atmospheric turbulence conditions. The atmospheric turbulence was generated by the simulation of spatial light modulator. The contrast of interferewithout atmospheric turbulence was compared under four modulation depths of 26. 32%,42. 04%, 67. 59% and 85. 04%, respectively. The results show that,the deeper the modulation level of modulation signal i s,the stronger its ability to resist atmospheric turbulence is. The conclusion has some reference significance for the selection of dual frequency lidar light sources.