基于TDLAS甲烷遥测的数字锁相电路设计

Design of digital phase-locked circuit for TDLAS methane telemetry

针对以往甲烷测量系统体积庞大、探测距离较近的缺点,提出了基于分布式反馈激光器(DFB)的天然气运输管道安全检测方法及电路设计。重点对基于现场可编程门阵列(FPGA)的正交数字锁相放大器进行设计以及分布式反馈激光器驱动电路和温控电路进行改进设计,并对FPGA核心控制电路、激光器驱动电路以及温控电路进行理论研究与实验验证。采用一次谐波和二次谐波比值计算激光路径中的气体浓度。实验结果表明:系统的最低探测浓度达到20×10^(-6),探测距离达到40 m,实现系统远距离、高精度探测。

Aiming at disadvantages of large size and close detection distance of previous methane measurement systems,propose a methed and circuit design using distributed feedback laser( DFB) for safety detection of gas pipeline. Focusing on design of orthogonal digital phase-locked amplifier based on field programmable gate array( FPGA) and improved design of distributed feedback laser drive circuit and temperature control circuit,theoretical research and experimental verification on FPGA core control circuit,laser drive circuit and temperature control circuit are conducted. The ratio of first harmonic and second harmonic is used to calculate the gas concentration in the laser path. The experimental results show that the minimum detecting concentration of the system reaches 20 × 10-6,and the detecting distance can reach 40 m,and the long-distance and high-precision detection requirements of the system are met.