可调谐二极管激光吸收光谱二次谐波信号的模拟与分析

可调谐二极管激光吸收光谱技术(TDLAS)作为近年来发展起来的一种气体检测技术，具有高分辨率、高灵敏度和快速测量等特点。波长调制光谱信号的二次谐波分量常作为检测信号，用于气体浓度信息的反演。利用MATLAB中的可视化建模仿真平台Simulink，模拟了基于TDLAS的波长调制光谱信号，利用锁相放大原理提取二次谐波分量。采用数字锁相，正交双通道结构实现锁相算法。通过比较不同调制系数下二次谐波信号的变化情况，分析了二次谐波信号与调制系数的关系，以便确定最佳参数，用于二次谐波的提取。

Simulation and Analysis of Second-Harmonic Signal Based on Tunable Diode Laser Absorption Spectroscopy

Tunable diode laser absorption spectroscopy (TDLAS) is a new gas detection technique developed recently with high spectral resolution, high sensitivity and fast time response. The second-harmonic signal of wavelength modulation spectroscopy (WMS) is often used as the detection signal for gas concentration inversion. Using Simulink, a visual modeling and simulation platform, the authors simulated the WMS signal based on TDLAS, and got the second-harmonic signal by using lock-in amplifier algorithm. Digital orthogonal algorithm was studied in this paper. The relationship between second-harmonic signals and the modulation indexes was analyzed by comparing changes of second-harmonic under different modulation indexes, in order to find out the optimized parameters for second-harmonic detection.