Design And Implementation Of A High-Speed FPGA-Based Phasemeter With Broad Bandwidth

Space gravitational wave detection currently is a hot topic around the world,and its main detection technology is laser differential interferometry ranging technology which observes gravitational waves by reflecting the influence of gravitational waves on the arm length of the interferometric arm in the interference signal phase.As the key technology,phase measurement system is an important issue of research.This thesis analyzes the Gravitational wave detection system and detection requirements as well as constraints of LISA/e LISA,Tianqin and Taiji,and compares various phase measurement techniques,then determines the high compatibility between phase-locked loop technology and detection projects,and proposes a phase measurement technology scheme with high speed,high precision and broad bandwidth.Compared to analog phase-locked loops,digital phase-locked loops have significant advantages in high-precision measurement.This thesis designs digital phase-locked loops based on the principle of phase-locked loops.MATLAB software is used to assist in the design,such as optimizing the loop model and design parameters.After analyzing the steady-state phase difference of different types of signals,a secondorder phase-locked loop is determined as the main part of the phasemeter.Due to the parallel processing characteristics of FPGA,a phase-locked loop model is built on the Vivado platform using Verilog HDL hardware description language and FPGA as the hardware carrier.The model is simulated by Modelsim and verified on the board.The experimental results show that the fast-capture time of the phase-locked loop is about15 μs.The fast-capture bandwidth is between 175 k Hz and 200 k Hz,with a phase accuracy of approximately 6 μrad.In order to extend the bandwidth of the phase-locked loop to match the detection requirements,this thesis designs an optimization scheme by measuring frequency using sine curve fitting,and verifies the feasibility of the scheme through theoretical analysis and simulation,which performs well within a range of 10% deviation from the frequency of the input signal.Then prototype of phasemeter based on optimization scheme is developed on Vivado,and through simulation it can be seen that the bandwidth of PLL has been expanded from less than 200 k Hz to over 500 k Hz,and it is not the limit theoretically.The optimized phasemeter achieves fast phase measurement and wide range frequency tracking.The software simulation results and hardware experimental data show that the FPGA-based digital phase-locked loop can realize phase locking with high accuracy of 6 μrad and broad bandwidth ranging from 2 MHz to 25 MHz theoretically.