Processing laser Doppler signal with a digital filter

We can use laser Doppler effect to measure velocity. But the volume of laser Doppler signal is small and the signal-to-noise is small. If we use an analog filter to process laser Doppler signal. It is difficult to change the frequency response of the analog filter. So it is difficult to get a good signal. In this paper, we use a digital filter to process laser Doppler signal. When we measure the velocity, we can get the laser Doppler signal volume by an analogy-digital converter. We can process the signal by a Chebyshev digital filter and save the signal in RAM. The digital filter's frequency response can be changed easy until we get a good Doppler signal. In this paper, we show how to design the chebyshev digital filter and how to use the filter to process the laser Doppler signal.