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

An analog-digital hybrid and lock-in amplifier technology, which is applied in amplifiers, parametric amplifiers, amplifier types, etc., can solve the problems of difficult detection and high cost of digital lock-in amplifiers, meet the requirements of low production cost, reduce sampling rate, and reduce hardware required effect

Active Publication Date: 2014-10-08
SYSU CMU SHUNDE INT JOINT RES INST +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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 am...

Method used

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

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Embodiment 1

[0064] refer to Figure 4 , a lock-in amplifier with an analog-digital hybrid structure, comprising an input signal processing system 100, a reference signal generation system 200, an analog processing system 300, an analog-to-digital conversion system 400 and a digital processing system 500, the first output of the reference signal generation system 200 The output terminal and the second output terminal output two mutually orthogonal sine wave reference signals;

[0065] The analog processing system 300 includes a first analog multiplier 31, a second analog multiplier 32, a first analog low-pass filter 41 and a second analog low-pass filter 42, and the analog-to-digital conversion system 400 includes a first analog-to-digital converter 51 And the second analog-to-digital converter 52, the digital processing system 500 includes a first digital low-pass filter 61, a second digital low-pass filter 62 and a digital operator 7;

[0066] The input terminal of the input signal proc...

Embodiment 2

[0083] A lock-in amplification method of a lock-in amplifier with an analog-digital hybrid structure of Embodiment 1, comprising:

[0084] S01. Buffering the input signal, if the input signal is a current signal, converting it into a voltage signal at the same time;

[0085] S02. Perform filtering and signal amplification on the buffered input signal in sequence.

[0086] S1. The reference signal generation system generates two mutually orthogonal sine wave signals, and then multiplies the two mutually orthogonal sine wave signals by the input signal to obtain two analog voltage output signals.

[0087] Suppose the equation of the input signal is:

[0088]

[0089] Among them, S i (t) represents the input signal, Indicates the signal to be tested in the input signal, A i , ω, are the amplitude, angular frequency and phase of the signal to be measured; B i (t) is the noise portion of the input signal.

[0090] Assume that the two mutually orthogonal sine wave signal...

Embodiment 3

[0112] The lock-in amplifier of embodiment one is applied in the signal acquisition of multi-frequency atomic force microscope (AFM), because multi-frequency AFM is in use, excited the intrinsic mechanical vibration of the multiple frequencies of AFM micro-cantilever probe, needs simultaneously Detect the magnitude and phase of the signal at these frequencies. The frequency of each intrinsic mechanical vibration commonly used in AFM microcantilever probes is usually in the range of 10 kHz to 10 MHz. For the detection of a certain frequency signal, the signals of other frequencies are interference signals, and the distance between the frequencies is relatively close, for example, about 6 times, which is not conducive to the improvement of precision for the phase-locking detection technology. In the analog phase-locking mode, the frequency characteristics of the analog filter make it difficult to filter out adjacent frequency signals. The lock-in amplifier with an analog-digita...

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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...

Claims

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Application Information

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IPC IPC(8): H03F7/00H03L7/00
Inventor 丁喜冬冯昊轩陈弟虎王自鑫郭建平
Owner SYSU CMU SHUNDE INT JOINT RES INST
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