Digital phase lock amplifier

Abstract

The invention discloses a digital phase lock amplifier which comprises a signal passage (1), a reference passage (2) and a signal processor (3), wherein the signal passage (1) is connected with the signal processor (3) through an analog to digital converter (4); the signal processor (3) comprises a frequency measurement module (31), a phase detection discriminator (32), a Cordic generator (33), and a first low pass filter (34) and a second low pass filter (34'). The reference passage (2) forms two paths to output to the signal processor (3) through a signal shaping circuit module (22); one path of the reference passage (2) is input to the Cordic generator (33) through the frequency measurement module (31), and the other path of the reference passage (2) is input to the Cordic generator (33) through a phase shifting module (7) and the phase detection discriminator (32); and the sine and cosine signals output by the Cordic generator (33) are multiplied by the input signal of the signal passage (1) respectively, and are output through the first and second low pass filters (34 and 34') and digital to a first D / A converter (5) and a second D / A converter (5') in sequence. Compared with the prior art, the digital phase lock amplifier has the advantages of high precision, wide frequency band and stable data, and improves the phase precision and eliminates the frequency nonlinearity of an analog channel.

Description

technical field [0001] The invention relates to the field of weak signal detection and amplification equipment, in particular to a digital lock-in amplifier based on a cross-correlation algorithm. Background technique [0002] Lock-in amplification technology is the most widely used and most effective method in weak signal detection. The basic idea of ​​lock-in amplification technology to measure weak signals mainly has two points. One is to use the reference signal to modulate the slow-changing or DC signal to realize frequency migration. Due to the existence of a large amount of noise in the daily environment, these noises have a certain distribution in the frequency domain, and the noise has a larger amplitude in the low frequency stage. If the frequency of the signal to be measured is low or a DC signal, the noise will inevitably be amplified when the measurement signal is amplified. If the AC amplification is used, these noise frequency areas with large amplitude can...

AI Technical Summary

Problems solved by technology

The digital lock-in amplifier uses an average value filter to achieve phase-sensitive correlation detection, but the low-pass cut-off frequency of the average filter is low, the attenuation slope is large, and the required order is more than that of the IIR filter, and the effect is not ideal.

In addition, the square wave signal used in the digital lock-in amplifier needs to be converted into a digital signal, and then input to the signal processor for multiplication and integration operations with the reference signal of the reference channel. Due to the defects of error and low phase accuracy caused by signal conversion

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