先放子函數：

function [C, B, A, rM] = dir2fs_r(h, r);% DIRECT-form to Frequency Sampling form conversion % ----------------------------------------------------------% [C, B, A, rM] = dir2fs_r(h, r)% C = Row vector containing gains for parallel sections% B = matrix containing numerator coefficients arranged in rows% A = matrix containing denominator coefficients arranged in rows% h = impulse response vector of an FIR filter% rM = r^M factor needed in the feedforward loop% r = radius of the circle over which samples are taken (r<1)M = length(h); H = fft(h, M);magH = abs(H); phaH = angle(H)';% check even or odd Mif (M == 2*floor(M/2))L = M/2-1; % M is even%A1 = [1, -1, 0; 1, 1, 0];A1 = [1, -r, 0; 1, r, 0];C1 = [real(H(1)), real(H(L+2))];elseL = (M-1)/2; % M is odd%A1 = [1, -1, 0];A1 = [1, -r, 0];C1 = [real(H(1))]; endk = [1:L]';% initialize B and A arraysB = zeros(L, 2); A = ones(L, 3);% compute denominator coefficientsA(1:L, 2) = -2*r*cos(2*pi*k/M);A(1:L, 3) = r*r;A = [A;A1];% compute numerator coefficientsB(1:L,1) = cos(phaH(2:L+1));B(1:L,2) = -r*cos(phaH(2:L+1) - (2*pi*k/M));% compute gain coefficientsC = [2*magH(2:L+1), C1]';rM = r^M;

　　再放主函數：

%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %% Output Info about this m-file fprintf('\n***********************************************************\n'); fprintf(' <DSP using MATLAB> Problem 6.20 \n\n');banner(); %% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %format long; format short; fprintf('\n FIR filter DIRECT-form: \n'); h = [1, 2, 3, 2, 1]/9; b = h a = 1.0fprintf('\nConvert DIRECT-form to PARALLEL-form : \n'); [C, Bp, Ap] = dir2par(b, a)if size(C)==0C = 0; endfprintf('\nConvert DIRECT-form to CASCADE-form : \n'); [b0, Bc, Ac] = dir2cas(b, a) fprintf('\nConvert TF-form to SOS-form : \n'); [sos, g] = tf2sos(b, a)% ---------------------------------------------------------- % NOTE: linear-phase can not use LATTICE-form % ---------------------------------------------------------- fprintf('\nConvert DIRECT-form to All-Zero LATTICE-form : \n'); [Klc] = dir2latc(b) fprintf('\nConvert DIRECT-form to FREQUENCY-SAMPLE-form 1 : \n'); [Cfs, Bfs, Afs] = dir2fs(b) fprintf('\nConvert DIRECT-form to FREQUENCY-SAMPLE-form 2 : \n'); r = 0.9; [Cfs_r, Bfs_r, Afs_r, rM] = dir2fs_r(b, r) % ----------------------------------------- % START check % ----------------------------------------- n = [0:7]; delta = impseq(0, 0, 7) %format long format short hcas = casfiltr(b0, Bc, Ac, delta)hltc = latcfilt(Klc, delta)%hladr = ladrfilt(Klr, Clr, delta)hdir = filter(b, a, delta) % ------------------------------------------- % END check % -------------------------------------------

　　運行結果：

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轉載于:https://www.cnblogs.com/ky027wh-sx/p/10264126.html

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