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FIR filter coefficients

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Talha on 6 Jul 2011
Answered: Veera Kanmani on 20 Apr 2018
I am trying to implement digital FIR filter in my DSP kit.I know the order, sampling frequency and my signal bandwidth. I want to design Multi band pass filter.
Currently I am working on "fdatool" in Matlab for FIR filter designing. I am trying to make two filter convolve and then get the desired results. One LPF and other bandpass. I successfully get the coefficients in the Matlab workspace and the result of convolution is to some extent satisfactory but the problem is I don't know anything about the filter structure that is used by the original source codes. Cause when I copied the coefficients from the source file and then implemented it Matlab the result was as expected, but when I change the filter structure like Direct or Transpose or anything, nothing happens as oppose to my designed filters whose respone changes as I change the structure.
What could be the reason for that...
Honglei Chen
Honglei Chen on 7 Jul 2011
Hi Talha,
Did you try to look at the response of filter before you burnt the code? Do you see a notch at 50Hz? In addition, do you really have to do it in an FIR filter? From your spec, I'd try a notch filter rather than cascading a lowpass and a bandpass together. Type the following command for details if you have Filter Design Toolbox or DSP System Toolbox.
help fdesign.notch
Talha on 8 Jul 2011
yes the response was pretty close to good actually. The notch was at 50 Hz. and Yes I require a FIR cause its the only one that is supported by the DSP. And a notch is only available in IIR.

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Answers (1)

Veera Kanmani
Veera Kanmani on 20 Apr 2018
Use FDA tool

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