How to generate your own filter?

Custom filter can be made using Matlab or by contacting us. The filter coefficient file format is the same as the Matlab mat-format, but change the extension name from .mat to .emp. An example on generating and saving filter coefficients in Matlab is given below. Note that this generates a filter that is unstable if it is inverted so it can only be used for pre-filtering, not for post-filtering (since the post-filtring uses the inverted filter). Since the purpose of this filter is to band-limit the output below 80 Hz, this is no problem for this application.

Fs=48000; % Sampling frequency in Hz

FcutOff = 80; % Cutoff frequency in Hz

Wn= FcutOff/(Fs/2); % Normalized cutoff frequency

FilterOrder = 6; % Filter order

FilterType = 'high'; % Filter Type

[b,a] = BUTTER(FilterOrder,Wn, FilterType); % Generate filter

save HighPassFc80Hz_Fs48000Hz.emp a b -mat

To use this filter, run the code and copy the generated file ‘HighPassFc80Hz_Fs48000Hz.emp’ to the ‘Filters’-folder under the WinMLS-folder.