신호처리 | 버터워스 원형 필터를 사용한 디지털 저역통과 필터 설계 |
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작성자 cemtool 작성일14-04-23 19:01 조회10,728회 댓글0건본문
버터워스 원형 필터를 사용하여 다음 사양을 만족하는 디지털 저역통과 필터를 설계해보자.
- ex8_11.cem
/* Chapter 8: Example 8.11 Impulse Invariance Transformation Butterworth Lowpass Filter Design */ % Digital Filter Specifications:wp = 0.2*pi; % digital Passband freq in Hzws = 0.3*pi; % digital Stopband freq in HzRp = 1; % Passband ripple in dBAs = 15; % Stopband attenuation in dB % Analog Prototype Specifications: Inverse mapping for frequenciesT = 1; % Set T=1OmegaP = wp * T; % Prototype Passband freqOmegaS = ws * T; % Prototype Stopband freqep = sqrt(10^(Rp/10)-1); % Passband Ripple parameterRipple = sqrt(1/(1+ep*ep)); % Passband RippleAttn = 1/(10^(As/20)); % Stopband Attenuation % Analog Butterworth Prototype Filter Calculation:[cs,ds] = butlpf(OmegaP,OmegaS,Rp,As); //*** Butterworth Filter Order = 6 % Impulse Invariance transformation:[b,a] = implinv(cs,ds,T); [C,B,A] = drt2prl(b,a) % Plotting figure; subplot(1,1,1)[db,mag,pha,grd,w] = mfreq_z(b,a); subplot(2,2,1); plot(w/pi,mag); title("Magnitude Response")xtitle("frequency in pi units"); ytitle("|H|"); subplot(2,2,2); plot(w/pi,pha/pi); title("Phase Response")xtitle("frequency in pi units"); ytitle("pi units"); subplot(2,2,3); plot(w/pi,db); title("Magnitude in dB"); xtitle("frequency in pi units"); ytitle("decibels") subplot(2,2,4); plot(w/pi,grd); title("Group Delay")xtitle("frequency in pi units"); ytitle("Samples");
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