Digital phase-locked amplifier combined with ratio operation

Abstract

The invention discloses a digital phase-locked amplifier combined with ratio operation and a lock-in amplification method thereof. The phase-locked amplifier comprises an input signal processing module, a reference signal generation module, an analog-to-digital conversion module and a digital processing module, the reference signal generation module outputs two paths of sine reference signals which are orthogonal to each other, and the digital processing module comprises a digital multiplier, a digital low-pass filter and a digital arithmetic unit. A wide signal input range can be achieved inthe signal detection process, the bandwidth requirement for a front-end amplification circuit is effectively lowered, and power consumption is reduced. By adopting ratio operation, the fluctuation gain brought by multiplicative noise in the circuit can be counteracted, so that the signal-to-noise ratio of the circuit is effectively improved. The invention 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 digital lock-in amplifier combined with ratio operation. 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 in the signal with the same frequency or multiplied frequency as the reference signal have a response, which can greatly suppress the noise and improve the signal-to-noise ratio of the detection signal. The basic principle of lock-in amplifier is as follows figure 1 As shown, where the phase-sensitive detector is usually composed of a multiplier and an integrator, and the integrator is usually implemented with 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 ...

AI Technical Summary

Problems solved by technology

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

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