中文摘要：

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。

英文摘要：

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.