MATLAB Files.rar_DSP

% Inputs: N -- filter length (odd integer) % f_type -- 1 for lowpass, 2 for highpass, 3 for bandpass, % and 4 for bandstop. % f_para -- omega_c for types 1 and 2, [omega_c1 omega_c2] for % types 3 and 4. % w_type -- 1 for von Hann window, 2 for Hamming window, 3 for % Blackman window and 4 for Kaiser window. % b -- beta for Kaiser window (optional). % Output: h -- filter's impulse response (coefficients). % Written by W.-S. Lu, University of Victoria % Last modified: Dec. 18, 2002. % Examples: h = win_fourier(71,1,0.6,2); % h = win_fourier(71,2,0.5,3); % h = win_fourier(71,3,[0.35 0.65],4,5); % h = win_fourier(71,4,[0.3 0.7],4,5); function h = win_fourier(N,f_type,f_para,w_type,b) M = (N-1)/2; n = 0:M-1; % Generate impulse response of the ideal filter if f_type == 1, % lowpass omec = pi*f_para; hd = sin((n-M)*omec)./((n-M)*pi); hd = [hd omec/pi fliplr(hd)]; elseif f_type == 2, % highpass omec = pi*f_para; hd = -sin((n-M)*omec)./((n-M)*pi); hd = [hd 1-omec/pi fliplr(hd)]; elseif f_type == 3, % bandpass omec1 = pi*f_para(1); omec2 = pi*f_para(2); hd = (sin((n-M)*omec2) - sin((n-M)*omec1))./((n-M)*pi); hd = [hd (omec2-omec1)/pi fliplr(hd)]; elseif f_type == 4, % bandstop omec1 = pi*f_para(1); omec2 = pi*f_para(2); hd = (sin((n-M)*omec1) - sin((n-M)*omec2))./((n-M)*pi); hd = [hd 1-(omec2-omec1)/pi fliplr(hd)]; end % Geneate window function if w_type == 1, % von Hann w = 0.5*(1-cos(pi*n/M)); w = [w 1 fliplr(w)]; elseif w_type == 2, % Hamming w = 0.54 - 0.46*cos(pi*n/M); w = [w 1 fliplr(w)]; elseif w_type == 3, % Blackman w = 0.42 - 0.5*cos(pi*n/M) + 0.08*cos(2*pi*n/M); w = [w 1 fliplr(w)]; elseif w_type == 4, % Kaiser w = besseli(0,b*sqrt(1-(n/M-1).^2))/besseli(0,b); w = [w 1 fliplr(w)]; end % Obtain impulse response h = w.*hd; figure(1) subplot(121) plot(h) axis([1 N 1.25*min(h) 1.25*max(h)]) axis('square') grid title('Impulse response of the FIR filter') % Evaluate frequency response of the filter and plot [H,w] = freqz(h,1,1024); subplot(122) plot(w,20*log10(abs(H))) axis([0 pi -100 10]) axis('square') grid title('Amplitude response of the FIR filter') xlabel('Normalized Frequency')