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작성자 cemtool 작성일14-04-23 19:11 조회10,916회 댓글0건본문
디지털 타원형 저역통과 필터 설계
- ex8_24.cem
/* Chapter 8: Example 8.24 Elliptic Lowpass Filter Design: Use of the ELLIP function */ /* Digital Filter Specifications: */ wp = 0.2*pi; /*digital Passband freq in Hz */ ws = 0.3*pi; /*digital Stopband freq in Hz */ Rp = 1; /*Passband ripple in dB */ As = 15; /*Stopband attenuation in dB */ /* Analog Prototype Specifications: */ T = 1; /*Set T=1 */ OmegaP = (2/T)*tan(wp/2); /*Prewarp Prototype Passband freq */ OmegaS = (2/T)*tan(ws/2); /*Prewarp Prototype Stopband freq */ /* Analog Elliptic Filter order calculations: */ ep = sqrt(10^(Rp/10)-1); /*Passband Ripple Factor */ A = 10^(As/20); /*Stopband Attenuation Factor */ OmegaC = OmegaP; /*Analog Prototype Cutoff freq */ k = OmegaP/OmegaS; /*Analog Prototype Transition Ratio; */ k1 = ep/sqrt(A*A-1); /*Analog Prototype Intermediate cal. */ // capk = ellipke([k.^2 1-k.^2]); // capk1 = ellipke([(k1 .^2) 1-(k1 .^2)]); capk = ellipke([k.^2 1-k.^2]); %elp_k([k.^2 1-k.^2]); capk1 = ellipke([(k1 .^2) 1-(k1 .^2)]); %elp_k([(k1 .^2) 1-(k1 .^2)]); N = ceil(capk(1)*capk1(2)/(capk(2)*capk1(1))); msgprint("*** Elliptic Filter Order = ") N /* Digital Elliptic Filter Design: */ wn = wp/pi; /*Digital Passband freq in pi units */ [b,a]=ellip(N,Rp,As,wn); [b0,B,A] = drt2cas(b,a)
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