A Digital Signal Processing Algorithm For Broadband Signal Of Pulsed Coherent Wind Lidar

Pulse coherent lidar, application of coherent technology with Doppler frequency inthe atmosphere echo signal and the vibration reference signal. The purpose is receivingDoppler frequency and applying digital signal processing technology in frequencyanalysis. To obtain the value closing to the true wind field information estimated.In this paper, the main research content is dealing with broadband (40MHz) radarecho signal, according to digital intermediate frequency coherent technology, this papergives two kinds of broadband intermediate frequency echo signal scheme, andsimulation experiment on Matlab environment. According to the atmosphere of the echosignal with very low SNR, pretreatment signal is weak, therefore, simulating the signalwith low SNR on Matlab environment and Doppler frequency extraction of information.First of all, introducing pulse coherent laser wind measurement lidar works and thebasic theory of signal processing. Here introduces the role of the atmosphere on thepulse signal attenuation, echo signal analog-digital conversion sampling theory ofdigital signal processing module, center frequency receiver theory, and digitaldown-conversion principle.Then, according to the specific parameters of the intermediate frequency and thesignal bandwidth of the subject, apply bandpass sampling theory and the convenience ofdigital control oscillator to design sampling rate. And based on the digital signalprocessing theory, design low-pass filter, design two options for broadband echo signaldigital frequency down conversion, digital mixing law and polyphase filtering.Again, the SNR of atmospheric echo signal between-40dB and-20dB, Such aweak signal with very low SNR, Simulation atmospheric echo signal on Matlabenvironment, Explain the affect of SNR to the spectral analysis. Analysis different pulserepetition period of the random phase problem, remove the random phase, researchsignal extraction method that coherent accumulation of methods to improve SNR ofsignal.Finally, with two broadband echo signal processing algorithms proposed for thisproject, carry on Matlab environment software simulation experiment Respectively.Consider the SNR and random phase of combination factors, use the control variablemethod including the number of coherent accumulation and the SNR factors to analysisecho signal processing. And analysis of the pros and cons compare to the twoalgorithms, the premise of obtain wind speed information, the standard deviation ofpolyphase filtering less than1m/s, it’s a better broadband signal processing method.