延 安大学数字信号处理课件Chapter 6 IIR Digital Filter Design.pptVIP

* 6.7 IIR digital filter design using MATLAB % Program 9_1 % Elliptic IIR Lowpass Filter Design % Wp = input(Normalized passband edge = ); Ws = input(Normalized stopband edge = ); Rp = input(Passband ripple in dB = ); Rs = input(Minimum stopband attenuation in dB = ); [N,Wn] = ellipord(Wp,Ws,Rp,Rs) [b,a] = ellip(N,Rp,Rs,Wn); [h,omega] = freqz(b,a,256); plot (omega/pi,20*log10(abs(h)));grid; xlabel(\omega/\pi); ylabel(Gain, dB); title(IIR Elliptic Lowpass Filter); * 6.7 IIR digital filter design using MATLAB % Program 9_2 % Type 1 Chebyshev IIR Highpass Filter Design % Wp = input(Normalized passband edge = ); Ws = input(Normalized stopband edge = ); Rp = input(Passband ripple in dB = ); Rs = input(Minimum stopband attenuation in dB = ); [N,Wn] = cheb1ord(Wp,Ws,Rp,Rs); [b,a] = cheby1(N,Rp,Wn,high); [h,omega] = freqz(b,a,256); plot (omega/pi,20*log10(abs(h)));grid; xlabel(\omega/\pi); ylabel(Gain, dB); title(Type I Chebyshev Highpass Filter); * 6.7 IIR digital filter design using MATLAB % Program 9_3 % Design of IIR Butterworth Bandpass Filter % Wp = input(Passband edge frequencies = ); Ws = input(Stopband edge frequencies = ); Rp = input(Passband ripple in dB = ); Rs = input(Minimum stopband attenuation = ); [N,Wn] = buttord(Wp, Ws, Rp, Rs); [b,a] = butter(N,Wn); [h,omega] = freqz(b,a,256); gain = 20*log10(abs(h)); plot (omega/pi,gain);grid; xlabel(\omega/\pi); ylabel(Gain, dB); title(IIR Butterworth Bandpass Filter); * 6.8 Computer-Aided Design of IIR Digital Filters The IIR digital filter design algorithms described in Sections 9.2, 9.4, and 9.5 are based on the design of a prototype analog filter followed by its transformation to an IIR digital filter. These algorithms are used in applications requiring filters with a frequency-selective magnitude response with a lowpass, highpass, bandpass, or bandstop characteristics. * In applications requiring IIR digital filters with other types of frequency response, filter design algorithms rely on some type of iterati