Lock-in amplifier of analog-digital mixed structure and lock-in amplification method of lock-in amplifier

Abstract

The invention discloses a lock-in amplifier of an analog-digital mixed structure and a lock-in amplification method of the lock-in amplifier. The lock-in amplifier comprises an input signal processing system, a reference signal generation system, an analog processing system, an analog-to-digital conversion system and a digital processing system, wherein the first output end and the second output end of the reference signal generation system output two paths of sine wave reference signals which are mutually orthogonal; the analog processing system comprises two analog multipliers and an analog low-pass filter; the digital processing system comprises two digital low-pass filters and a digital operational unit. According to the lock-in amplifier, an aliasing signal is allowed to exist in a signal detection process; through the combination of the analog low-pass filter and the digital low-pass filters, an interference signal in an input signal can be effectively filtered, and a high-frequency interference signal and the aliasing signal are filtered, so that various frequency signals can be detected, the signal to noise ratio is effectively improved, hardware requirements are reduced, and the production cost is lower; the lock-in amplifier can be widely applied to the field of weak signal measurement.

Description

technical field [0001] The invention relates to the field of lock-in amplifiers, in particular to a lock-in amplifier with an analog-digital hybrid structure. Background technique [0002] Lock-in Amplifier, Lock-in Amplifier, abbreviated as LIA, is an amplifier for phase-sensitive detection of weak signals. Those noise components of the same frequency or multiplied frequency as the reference signal in the signal have a response, which can greatly suppress the noise and improve the signal-to-noise ratio of the detection. The basic block diagram of a lock-in amplifier is as follows: figure 1 As shown, where the phase-sensitive detector usually consists of a multiplier and an integrator, and the integrator usually uses a low-pass filter, figure 1 The lock-in amplifier adopts the principle of cross-correlation detection, and its basic working principle is as follows: [0003] According to the definition of the cross-correlation function, it is assumed that the input signal i...

AI Technical Summary

Problems solved by technology

However, due to the sampling theorem, the sampling rate of the analog-to-digital converter used must be at least twice the highest signal frequency, plus it is limited by the computing power of the processing components of the digital part, digital lock-in amplifiers are usually only applicable In the detection of low-frequency signals, for signals with higher frequencies, such as frequencies above MHz, digital lock-in amplifiers are difficult to achieve detection or can achieve detection but the cost is extremely high

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