| Description |
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% DESCRIPTION:
% ============
% FIR digital filter is designed using the frequency response masking
% technique [1,2] resulting in significant savings in number of multipliers
% used to implement the FIR filter. Savings is exceptional when the normalized
% transistion width is less than 1/16. The resulting structure of the filter
% can be found in [1].
%
% If any errors are found, please let me know. I have not tested it exhaustively.
%
% ChinSoon
%
% USAGE:
% ============
% [Fa Fma Fmc] = firfrm(pb,sb,pbRip,sbRip,fs);
% Inputs:
% pb - passband of the desired FIR filter in the same units as fs
% sb - stopband of the desired FIR filter in the same units as fs
% pbRip - maximum allowable passband ripple in linear magnitude
% sbRip - maximum allowable stopband ripple in linear magnitude
% fs - sampling frequency in Hz, kHz, MHz, etc.
%
% Outputs:
% Fa - contains the filter taps for the interpolated filter
% Fma - contains the filter taps for the masking filter for interpolated filter
% Fmc - contains the filter taps for the masking filter for complementary
% interpolated filter
%
% EXAMPLE CALL:
% ============
% [Fa Fma Fmc] = firfrm(2800,2850,0.01,0.01,10000);
%
% REFERENCES:
% ============
% [1] Y. C. Lim, "Frequency-response masking approach for the synthesis of
% sharp linear phase digital filters," IEEE Trans. Circuits Syst., vol.
% CAS-33, pp. 357-364, Apr. 1986.
% [2] Y. C. Lim and Y. Lian, "The optimum design of One- and Two-Dimensional
% FIR filters using the frequency response masking technique," IEEE
% Trans. Circuits Syst.,vol. 40, No. 2,Feb 93.
%
% NOTES:
% ============
% 1. This function only designs lowpass filter. To implement highpass
% filter, please find the equivalent lowpass filter by shifting the
% magnitude response left or right by 0.5. Design this new lowpass filter
% then phase shift the final filter output.
% |
