面向空间激光干涉的多通道相位测量系统

Multi-channel phase measurement system for the space laser interferometry

空间引力波探测激光干涉系统由多路干涉仪组成,涉及到多组干涉信号的相位采集和读出,多通道相位测量系统是空间激光干涉的关键核心技术之一。本文从太极计划及其地基激光干涉实验需求入手,设计、搭建并测试了多通道相位测量系统。首先,给出多通道相位测量系统的软硬件设计,包括硬件架构设计、数字锁相环测相算法、软件架构设计等。其次,对多通道相位计进行时域功能测试,包括相位准确度和线性度。测试结果表明多通道相位测量系统在不同工况下的动静态相位线性度和准确度良好。最终,对多通道相位计进行不同通道、不同频率、不同幅值下的频域噪声测试。测试结果还表明本文设计的多通道相位计,在0.1 mHz~1 Hz频段内,相位噪声水平均优于2πurad/√Hz;不同通道之间具有很好的一致性,由通道差异或ADC芯片差异引入的相位噪声在目标频段内可以忽略不计;对于频率在5-25 MHz之间的任意干涉信号,相位计在目标频段内均满足需求。因此,该多通道相位测量系统满足空间引力波探测及地基干涉实验的需求。

In the space gravitational wave detection Taiji mission,a heterodyne laser interferometer is used to detect gravitational wave signals in the middle and low frequency bands.In the Taiji mission,the laser interferometry system is composed of multi-channel interferometers,which involves the phase acquisition and readout of multiple sets of the interference signals.Therefore,the multi-channel phase measurement system is one of the key core technologies of the space laser interferometry.In this paper,a multi-channel phase measurement system is proposed,designed and tested based on the requirements of the Taiji mission and its ground-based laser interferometry experiments.First,the hardware and software design of the multi-channel phase measurement system is given,including hardware architecture design,phase measurement algorithm based on digital phase-locked loop and its implementation on FPGA,software architecture design,etc.Second,a time-domain functional tests of the multi-channel phasemeter are performed,which includes the phase accuracy and linearity.The results show that the dynamic and static phase linearity and accuracy of the multi-channel phase measurement system under different working conditions are good.Finally,the fre-quency domain noise tests of different channels at different frequencies and different amplitudes are carried out.The results show that the phase noise level of the multi-channel phase meter designed in this paper is better than 2πurad/√Hz in the frequency band of 0.1 mHz−1 Hz.There is good consistency between different channels,and the phase noise introduced by channel differences or ADC chip differences is negligible in the target frequency band.For any interference signal with a frequency between 5−25 MHz,the phasemeter can meet the requirements within the target frequency band.Therefore,the multi-channel phase measurement system meets the requirements of space gravitational wave detection and ground-based interference experi-ments.At the same time,the research results of this paper also provide an experimental basis for expanding the phase measurement system with more channels in the future.