针对目前四频差动激光陀螺光学解调方案可靠性和温度特性差的特点，介绍一种基于FPGA的数字拍频解调方案。分析了四频差动激光陀螺数字拍频解调对电路系统的需求，对数字拍频解调的关键部件——低通滤波器进行了设计与实现。根据四频差动激光陀螺的特性参数计算滤波器的通带截止频率及阻带截止频率，使用MATLAB的滤波器设计和分析工具FDATool完成了有限冲击响应（FIR）数字滤波器的参数设计，并利用Xilinx公司的FPGA集成开发环境ISE实现FIR数字滤波器的片上系统设计。仿真和实验结果表明，所设计的FIR数字滤波器对四频差动激光陀螺的和频分量衰减达到-66 dB，满足四频差动激光陀螺拍频解调的需求，并有助于实现四频差动激光陀螺的小型化和数字化。

In order to overcome the problems of poor reliability and thermal sensitivity for the current optical separation system of four-frequency differential laser gyros, a digital signal demodulating system based on FPGA was presented. After analyzing the demands of signal demodulation for four-frequency ring laser gyro, the low-pass filter was designed in detail and was implemented, which was the key component of digital signal demodulating system. The pass band cut-off frequency and stop band cut-off frequency were calculated on the basis of parameters of four-frequency differential laser gyros. The parameter design of FIR filter was realized by using the FDATool of Matlab software, which is the design and analysis tool of filter. Using the FPGA integrated development environment (ISE), the proposed FIR digital filter was implemented via SOPC architecture. The simulation and experiment results show that the sum frequency component is reduced to -66 dB by designed FIR digital filter, and it meets the requirements of the digital signal demodulating system of four-frequency differential laser gyros, and it helps to realize the miniaturization and digitization of full digital four-frequency differential laser gyros.