空间引力波探测激光外差干涉信号模拟系统

Simulation system of a laser heterodyne interference signal for space gravitational wave detection

由于激光外差干涉测量系统光机平台无法模拟多普勒频移,并且商用信号发生器无法实现多种类、高复杂度的星间外差干涉信号模拟,不能对空间引力波探测的相位计进行全面测试。通过分析外差干涉信号的特性,研究信号模拟系统的实现原理及方法,设计了空间引力波探测激光外差干涉信号模拟系统。首先,应用直接数字合成器(DDS)模拟外差干涉信号。其次,通过频率偏移方式模拟多普勒效应,应用混合同余算法生成散粒噪声并调制到外差干涉信号中。最后,基于FPGA搭建系统硬件平台,通过示波器及频谱分析仪分析生成信号的时频特性。实验结果表明,信号模拟系统在2~20 MHz的频率范围内杂波抑制度为-53 dBc,谐波(二次)抑制达到-47 dBc,生成信号的时频特性符合理论预期,满足空间引力波探测相位计的地面测试需求。

the Due to the limitation of the optical-mechanical platform of the laser heterodyne interferometry system,the Doppler frequency shift cannot be simulated.Moreover,commercial signal generators cannot realize various types of high-complexity intersatellite heterodyne interference signal simulations.It is difficult to conduct ground tests of the phasemeter for space gravitational wave detection detailed.Therefore,the characteristics of heterodyne interference signals were analysed,the realization principle and method of the signal simulation system were studied,and then the simulation system of the laser heterodyne interference signal for space gravitational wave detection was designed.First,the simulation of the heterodyne interference signal was applied to the DDS.Then,the influence of the Doppler effect was simulated by offsetting the overall frequency.Next,based on the mixed congruential algorithm,shot noise was generated and modulated into the heterodyne interference signal.Finally,with the usage of FPGA,the system hardware platform was built.The time domain and frequency domain characteristics of the generated signals were analysed by an oscilloscope and a spectrum analyser.The experimental result shows that the spurious suppression of the system is-53 dBc and the harmonic suppression is-47 dBc at 2-20 MHz.The signal generated by the system is in good agreement with the expectations which satisfies the ground test requirements of the phasemeter for space gravitational wave detection.