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More digital filter work. I have removed the FIR (Finite Impulse Response) filter again, and replaced it with more IIR (Infinite Impulse Response) Filters.
Before I started working with IIR filters I had a 12 stage delay line for an FIR filter. I am now using that memory for 10 poles of IIR filters. It is organized as 5 two pole filters in series. Any of the two pole filters can be low pass, high pass, or band pass filters. I now have it set up as a 6 pole low pass filter and a 4 pole high pass.
This combination is working at least as well as the previous setup (2 pole low, 2 pole high, plus FIR) at reducing high frequency noise, and it should be even better at removing ground signals.
Having 5 two pole filters makes it very flexible. Some characteristics of the detector like best sweep speed and amount of ground rejection can be changed just by replacing filter coefficients. Unfortunately the coefficients are a pain to calculate. Right now I am rebuilding the program every time I want to change the numbers. Eventually I will have a table of filter coefficients for different conditions.
Robert
Before I started working with IIR filters I had a 12 stage delay line for an FIR filter. I am now using that memory for 10 poles of IIR filters. It is organized as 5 two pole filters in series. Any of the two pole filters can be low pass, high pass, or band pass filters. I now have it set up as a 6 pole low pass filter and a 4 pole high pass.
This combination is working at least as well as the previous setup (2 pole low, 2 pole high, plus FIR) at reducing high frequency noise, and it should be even better at removing ground signals.
Having 5 two pole filters makes it very flexible. Some characteristics of the detector like best sweep speed and amount of ground rejection can be changed just by replacing filter coefficients. Unfortunately the coefficients are a pain to calculate. Right now I am rebuilding the program every time I want to change the numbers. Eventually I will have a table of filter coefficients for different conditions.
Robert