Ac Weak Signal Detection Based On Correlation Principle

This paper introduced the characteristics of weak signal and the widely useddetection methods of weak signal. At the same time this paper analyzed the principle ofthe related theory in weak signal detection and gave an implementation scheme of weaksignal detection based on communication theory. This design used the LIA as the weaksignal extraction system. The target signal will be buried deep in the strong interferencenoise, so the LIA system is divided into two channels, one for signal channel, mainly tohave mixed with strong noise and interference signal to be measured by the preamplifierand filtering, and makes the input signal after the signal channel signal-to-noise ratio isimproved. The other path is a reference channel, mainly for the production and the weaksignal with the frequency of the reference signal in the design, DDS is used to generatethe reference signal step adjustable frequency, phase of the reference signal can beadjusted to meet the reference signal and the measured signal phase difference is zerorequirements through the design of phase shift module, two signals are fed by phasedetector, lock-in amplifier low-pass filter, the signal extracted from strong noisebackground function.This paper first introduces the detection method in weak signal detection,introduces the implementation of lock-in amplifier based on correlation detection, andcomposition of the lock-in amplifier and working principle were analyzed, and then thesystem scheme is determined according to the requirements, and has carried on thesimulation analysis; the next to complete the circuit design of each module, forelaborate on the various chip and the circuit is the key component used, finallycompletes the system debug and gives the test results. The system can detects50uVweak AC signal from100Hz to10KHz with the average deviation of18%.