太赫兹时域光谱技术(THz-TDS)其光导天线产生的信号与背景噪声相比极其微弱,需要采用锁相放大技术对信号进行放大处理.根据锁相放大的基本原理和太赫兹时域光谱系统的特点,设计出了基于AD630 的可编程THz-TDS 锁相放大系统,该系统能够根据使用要求提供合适的中心斩波频率和带宽值.通过实验得到了由模拟开关控制的可编程带通滤波器在不同中心斩波频率处的输出值和带宽的关系曲线,并通过模拟实验验证了系统对微弱信号的探测能力.最后,在光学延迟线移动速度为1 500 μm/s,连续扫描的情况下,采集到的THz 信号的信噪比在50 dB 左右.结果表明,该系统具有中心斩波频率和带宽可调,锁相效果好,体积小,便于太赫兹仪器的集成化等优点.

The signal from photoconductive antenna of the Terahertz Time-domain Spectroscopy technology (THz-TDS)is so small compared with the background noise that need amplification by the lock-in amplifier.According to the basic principle of the lock-in amplifier and the characteristics of the THz-TDS,the programmable lock-in amplifier system for THz-TDS based on the AD630 is put forward,which be able to update the chopping frequency and bandwidth according to different samples or working states.The curve between outputs for the programmable band-pass filter controlled by the analog switches on different chopping frequencies and bandwidth can be got by the experiments.And the system’s weak signal detection ability is got by the simulation experiments.At last,in the case of the time-delay line moving speed to 1500 μm/s and continuous scanning,the SNR of THz signal is about 50 dB.The result shows that the system has the advantages of adjustable chopping frequency and bandwidth,good lock-in effect,small volume and easy to be integrated.