Study On Signal Detection And Data Processing Techniques Of Laser Doppler Signals

In the engineering field,velocity measurement can be used to measure the dynamic characteristics of objects.The velocity technology based on the doppler effect is an important means of detection.The paper,in order to solve the problem that communication wavelength high-speed photoelectric detector design technology and high-speed Doppler signal collection and processing technologies are used as the main core technologies of fiber laser Doppler measurement,but China has made few researches and no good solutions,emphatically researches the photoelectric detector design schemes and Doppler signal processing algorithms,analyzes and designs the full-fiber laser Doppler measurement light paths,sets up the experimental measurement device,and makes the experimental verification of and precision analyses on the light paths,detectors and calculated algorithms to ensure the stability of the laser Doppler measurement technologies in the practical application.The main research contents are as follows:1.It compares four kinds of homodyne detection light paths,to solve the problems of great signal power loss and low Doppler signal contrast ratio of the full-fiber laser velocity interferometer.It analyzes the reflected light coupling ways and reference light generation ways;calculates the light path loss and Doppler signal contrast ratio;designs the contrast experiment of the four light paths,and measures the contrast ratios of the light losses and Doppler signals;and confirms the optimal light path according to the experimental analysis results.2.It introduces the operating principle of the high-speed photoelectric detector:regarding the problem of low SNR(Signal to Noise Ratio)of detector Doppler signals analyzes the influencing factors of SNR,and selects the InGaAs PIN-type photodiode as the photoelectric conversion device and also its working photovoltaic mode(zero bias);designs the prefixed and main amplifying circuits;and also introduces the notices for the detector PCB design.3.It analyzes three Doppler signal processing algorithms:instantaneous frequency estimation algorithm based on time-frequency distribution,Tikhonov regularization numerical differentiation algorithm and sine function fitting algorithm.According to the experimental results,the paper select the instantaneous frequency estimation method based on time-frequency analysis,and the rising-cosine weighted denoising algorithm is used as the signal digital denoising algorithm.4.It designs the full-fiber light path system and signal processing circuit board for the laser Doppler measurement system.The light path system adopts the 1550nm wavelength laser device,optical coupler,isolator and other optical fiber passive devices;the circuit board adopts FPGA as the core processor,and high AD and Ethernet as the date collection and transmission devices,and sets up the experimental device.Then,it regards loudspeaker and voice coil motor as the test objects to respectively verify the optical fiber light paths,photoelectric detectors and signal demodulation algorithms,and the results show that the detector,light path and circuit design is feasible,the signal processing algorithms satisfy the precision requirements,and the relative system measurement error is less than 1%.The experiment verifies the reliability and precision of the measurement system.