Research On Detection Technology Of Narrowband Weak Photocurrent Signal

With the advancement of science and technology,human beings are exploring deeper and deeper in various fields,and the challenges they face gradually increase.The detection of weak photocurrent is an important part of it.In recent years,the theory of weak signal detection has been greatly developed.Therefore,weak photocurrent detection has also made considerable progress.However,in actual industrial applications,the test environment of detection instruments cannot be well guaranteed.If the noise is too large and the photocurrent is too small,it will be quite difficult to effectively extract useful signals.Therefore,there are still many problems in photocurrent detection that need to be resolved:First,the weak photocurrent signal is usually submerged under the background of noise.With the improvement of market accuracy requirements,the system has a greater demand for the signal-to-noise ratio of the front-end detection circuit;second,the general weak photocurrent detection equipment The volume is large,the price is expensive and the requirements for external factors are high.In view of the above problems,this paper studies and analyzes the narrow-band weak photocurrent under the background of noise,and designs a corresponding detection circuit.The main work content is as follows:1.Research the principle of weak photocurrent detection,introduce the types of internal noise of electronic devices,and analyze the equivalent noise models of photodetectors and operational amplifiers.2.The overall design scheme and module division are given using the principle of lock-in amplifier and crystal filter.In the preamplifier circuit,the equivalent noise model of the transimpedance amplifier circuit is analyzed,and two noise suppression methods are proposed.Then,based on the signal characteristics of the subject,a preamplifier circuit based on LC parallel resonance is proposed.And the selection of key components in the preamplifier circuit and the PCB layout are introduced in detail.3.In order to ensure the spurious-free dynamic range of the mixed signal,a fifthorder elliptical low-pass filter is designed to make the SFDR of the mixed signal reach more than 80 d Bc,which ensures the spectral purity of signal modulation and demodulation;designed a phase shift The circuit controls the phase of the local oscillator signal from the perspective of hardware;a differential RF attenuation filter is designed using an instrumentation amplifier to ensure the accuracy of the demodulated signal.After the circuit board design is completed,the relevant parameters are analyzed and tested in combination with the project requirements and indicators,which verifies the feasibility of the design in this article.