高选择性便携式正交锁相放大器研制

针对商用锁相放大器或虚拟锁相放大器体积较大、价格昂贵，无法集成在便携式设备中的问题，利用信号相干检测原理，设计并研制了一种基于ARM7的便携式正交锁相放大器，包括两路参考信号相互正交的相敏检波器。为验证各电路功能，详细测量了各模块的输出信号波形。利用信号发生器模拟产生待测信号，对两路相敏检波器的输入输出关系做了标定，并重点对所研制锁相放大器的性能做了测试和表征，包括量程、均值误差、选频特性和检测下限等。实验结果显示，系统测量下限小于等于5mV，检测范围为5～3000mV，均值误差绝对值小于等于10mV，满度测量误差小于等于1％，待测信号允许带宽0—50kHz，3dB频带宽度小于1Hz，达到了便携式仪器的测量要求。

Development of High-Frequency-Selective Portable Orthogonal Lock-in Amplifier Device

Because of large size and high price, the commercially available lock-in amplifier or virtue lock-in amplifier cannot be integrated into portable devices. By using signal correlation detection principle, a portable quadrature lock-in amplifier is designed and developed based on ARM7 processor, which consists of two PSD （Phase Sensitive Detectors） with quadrature reference signals. Hardware modules are welded and debugged, including reference signal generator, analogue multiplicator, low-pass filter, etc. In order to prove the function of each module, output waveforms are measured and taken. Using the output sine-wave signal from a commercially available signal generator as the signal to be detected, the relations between input and output of the two PSDs are calibrated. The characteristics involving measurement scale, mean error, frequency selective property and detection limit are intensively tested and characterized. Experimental results show that, the detection limit on signal amplitude is less than 5 mV, the measuring scale is 5 -3 000 mV, the absolute mean error is less than 10 mV, the mean error relative to the measuring scale is smaller than 1%, the allowed bandwidth of the detected signal is 0 - 50 kHz, and the 3-dB bandwidth is less than 1 Hz. Because of good frequency selectivity and high accuracy, the proposed portable lock-in amplifier exhibits potential applications in weak signal detection, industrial control and instrumental devices.