Adaptive selection and test method for laser Doppler signal filtering bands

Abstract

The invention relates to Doppler signal processing, and aims to track the Doppler signal frequency in real time, effectively filters out base signals, realizes a large speed measurement range, and hashigh efficiency and low cost. The invention discloses an adaptive selection and test method for laser Doppler signal filtering bands, and comprises the steps of: dividing a passband of a filter intofour filtering bands according to the bandwidth of the Doppler frequency, wherein each filtering band is implemented by means of a fixed-bandwidth finite-length unit impulse response filter FIR; performing judgment selection on the four filtering bands in sequence, namely, executing the judgment selection according to a sequence of the filtering band 1, the filtering band 2, the filtering band 3 and the filtering band 4; and calculating a difference value between two moments, that is time spent on signal processing, calculating a maximum value of running speed variations of a tested object within time delta t according to the maximum acceleration of the tested object, calculating a maximum value delta fd of Doppler frequency variations at the next moment, and determining overlapping portions among the four filtering bands according to the maximum value of Doppler frequency variations. The adaptive selection and test method is mainly applied to speed measurement occasions.

Description

technical field [0001] The invention relates to an FPGA-based Doppler signal processing algorithm, in particular to an FIR-based filter band adaptive selection algorithm, in particular to a laser Doppler signal filter band adaptive selection method. Background technique [0002] When a beam of laser light is irradiated on the surface of an object, the frequency of the scattered laser light received by the object surface changes due to the moving speed of the object, that is, the Doppler frequency shift. Therefore, the relationship between the moving speed of the object and the Doppler frequency shift can be realized The measurement of the moving speed of an object can further realize the measurement of acceleration and length. [0003] When measuring the speed of an object, it is necessary to extract the laser Doppler frequency shift signal. Before extraction, it is often necessary to process the initial signal. The most important process is to filter out noise and backgroun...

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Problems solved by technology

[0004] Fixed bandwidth filtering is a common method of frequency signal processing. This method achieves the purpose of filtering noise by limiting the bandwidth of the measurement system. The advantage of this method is that it is easy to implement and simple in structure, but this technology is only applicable to signal spectrum and noise. On the premise that the frequency spectrum does not overlap, the signal and noise can be completely separated in this way, but the actual signal spectrum and noise spectrum often overlap, which is only applicable to the case where the signal frequency band is fixed, and the frequency of the Doppler signal follows the object The speed of the movement changes, especially when the speed change range is large, this method cannot filter out the base signal when measuring high speed; the average processing technology of the time domain signal, this method passes the signal when the noise signal is randomly distributed. The method of taking the average value of multiple measurements to filter out part of the noise, the advantage of this method is that the amount of calculation is relatively small, but this method is only suitable for the processing of low-frequency signals, and the frequency of the Doppler signal depends on the speed of the object , the faster the speed, the higher the frequency; autocorrelation detection technology, this technology is a technology that uses the periodicity of the signal and the randomness of the noise to remove the noise through autocorrelation and cross-correlation operations, especially suitable for detecting a large amount of random noise The periodic signal in the Doppler signal, but there is a base signal in the Doppler signal, and the base signal is also periodic, so this method cannot effectively filter out the base signal in the Doppler signal; the spectrum analysis method, the spectrum analyzer passes through The steps of filter amplification, frequency mixing, narrowband filter detection and smoothing are used to obtain the Doppler signal. This method has a high operating frequency bandwidth and does not require high signal-to-noise ratio. The frequency of the Puler signal always changes with the speed of the object, and this method has low information utilization rate, long measurement time, and low efficiency; wavelet transform technology, the parameters used in the noise reduction method based on wavelet transform need to be manually set, these The parameters are often obtained by experience, and cannot be automatically generated according to the respective characteristics of the signal and noise, so there is a certain complexity in using this method; when the adaptive filter requires more stages, the structure is complicated, and the parameter setting Sensitivity to the initial value of sum state; frequency tracking method, which amplifies uniformly in a wide frequency range, and performs narrowband filtering, which is easy to digitize in real time, but requires continuous signal and high signal-to-noise ratio, otherwise it may lose or wrongly track; optical frequency shift method , this method eliminates the substrate signal by adding an optical frequency shifting device (such as a rotating grating, an electro-optic device) in the optical path. The structure tends to be complicated

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