太赫兹测试系统中锁相放大电路的设计

The design of phase locked amplifier circuit in Terahertz test system

为了解决太赫兹时域光谱仪(TDS)所用锁相放大器方便携带和提取与太赫兹波电场强度相关微弱信号的问题,提出了一种基于互相关原理的锁相放大器设计方案。斩波器输出调制后的信号经前级放大滤波与通过移相电路的相干参考信号分别送入AD630的信号端和参考端,锁相后信号经低通滤波电路输出直流信号。测试结果表明:设计的锁相放大器具有良好线性度,可将信噪比为-60 d B的微伏级信号提取出来,能用于大背景噪声下太赫兹微弱信号的检测。

In order to solve the problem that the phase locked amplifier used in terahertz time domain spectroscopy （TDS） is convenient to carry and extract the weak signal of the electric field intensity of THz wave, a design scheme of phase locked amplifier is proposed based on cross correlation principle. The weak signal of the output of the chop- per is sent to the AD630 signal terminal through the pre-amplifier, and with the coherent reference signal though the phase shift circuit is sent to the AD630 reference terminal. After the phase locked, the voltage is converted into DC voltage by low pass filter. The experiment results show that the design of phase amplifier circuit has good linearity, can extract the millivolt signal with noise radio of - 60 dB, which can be used for the detection of the Terahertz weak signal in strong background noise.