passive RC highpass magnitude FRF to MATLAB FIR coefficients
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David W Purcell
on 4 Aug 2023
Commented: Star Strider
on 16 Aug 2023
Hello,
I have a GRASS EEG LP511 amplifier. It has a high-pass filter that is described as passive with 12 dB/octave slope. I imagine it is something like two simple RC high-pass filters in series. I can measure the magnitude frequency response function easily and I know the cut-off frequency (-6dB at 3 Hz).
I would like to implement this as an FIR filter in MATLAB.
I am having trouble sorting out how to obtain the FIR filter coefficients to match my analogue high-pass filter.
Could anyone help? Please assume I don't have a strong enough background and will need thorough explanations. Many Thanks! DP
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Star Strider
on 4 Aug 2023
I generally don’t design filters with such specificity, and so usually use relatively straightforward command-line functions. To design a filter such as yours, I would use the designfilt function (introduced in R2014a). It has a number of arguments, as well as ‘Filter Designer’, a GUI interface that can make this easier. (If you use Filter Designer, click on the ‘File’ tab and then click on ‘Generate MATLAB Code’ to use the filter code wtih the filtfilt function and your signal.) Use filtfilt to do the actual filtering regardless of how you design and code the filter.
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