Research On Zoom-FFT Used In Laser Doppler Velocimeter Based On DSP

The Laser Doppler Velocimeter(LDV) is a kind of precise instrument, whichis used to measure velocity of liquid and the moving objects. It is based onDoppler principle of light. It uses seeding particles to scatter the laser incident onit, then detects the change of the frequency of the scattered light by photoelectricdetector. Finally gets the velocity of fluid or moving object according the velocitywhich contained in the scattered light based on the frequency achieved isproportional to the velocity. The LDV has many merits, such as a rapid dynamicresponse, good space differentiating ability, wide measure range, high precision,its non-contact and real-time operation.For improving signal processing speed in LDV system to obtain highermeasure precision and real-time detection, a LDV signal processor using DSP asspectrum-analyzing processor was described based on hardware frame, signalprocessing and trial results, and the spectrum zoom processing in LDV has beeninvestigated. The technology of analyzing local magnitude—frequency of signalhas been developed rapidly in recently few years. As in the aspects of precision,efficiency, resolving power and agility, Zoom-FFT(ZFFT) is an effective methodto analyze local magnitude—frequency of signal, and it has been widely used. Inthis paper, the working principle of ZFFT has been introduced. A combinedmethod that is small sample ZFFT in addition to energy barycenter has beenrealized under MATLAB environment and been validated through simulation.The result shows that ZFFT is simple and feasible.TMS320VC5509 is used as the main controller in the LDV signal processorsystem. We have designed the circuit of preamplifier and filter, the A/D samplecircuit and DSP control module. The algorithm of FFT based on 2 is the mainmethod for signal processing.