基于MATLAB的滤波器设计

% Numerator coefficients are in vector num % Denominator coefficients are in vector den % Frequency values are returned in vector w % Gain values are returned in vector g w = 0:pi/255:pi; h = freqz(num,den,w); g = 20*log10(abs(h));

% Design of a Butterworth Bandstop Digital Filter Ws = [0.4 0.6]; Wp = [0.2 0.8]; Rp = 0.4; Rs = 50; % Estimate the Filter Order

[N1, Wn1] = buttord(Wp, Ws, Rp, Rs); % Design the Filter

[num,den] = butter(N1,Wn1,'stop'); % Display the transfer function

disp('Numerator Coefficients are ');disp(num); disp('Denominator Coefficients are ');disp(den); % Compute the gain response [g, w] = gain(num,den); % Plot the gain response plot(w/pi,g);grid axis([0 1 -60 5]);

xlabel('\\omega /\\pi'); ylabel('Gain in dB');

title('Gain Response of a Butterworth Bandstop Filter');