dir2cas.m

来自「很多matlab的源代码」· M 代码 · 共 43 行

function [b0,B,A] = dir2cas(b,a)
% DIRECT-form to CASCADE-form conversion(cplxpair version)
% --------------------------------------------------------------
% [b0,B,A] = dir2cas(b,a)
% b0 = gain coefficient
% B = K by 3 matrix of real coefficients containing bk's
% A = K by 3 matrix of real coefficients containing bk's
% b = numerator polynomial coefficients of DIRECT form
% a = denominator polynomial coefficients of DIRECT form
%
b0 = b(1);
b = b/b0;
a0 = a(1);
a = a/a0;
b0 = b0/a0;
M = length(b);
N = length(a);
if N > M
    b = [b zeros(1,N-M)];
elseif M > N;
    a = [a zeros(1,M-N)];
    N = M;
else
    NM=0;
end
K = floor(N/2);
B = zeros(K,3);
A = zeros(K,3);
if K*2 == N;
    b = [b 0];
    a = [a 0];
end
broots = cplxpair(roots(b));
aroots = cplxpair(roots(a));
for i = 1:2:2*K
    Brow = broots(i:1:i+1,:);
    Brow = real(poly(Brow));
    B(fix((i+1)/2),:) = Brow;
    Arow = aroots(i:1:i+1,:);
    Arow = real(poly(Arow));
    A(fix((i+1)/2),:) = Arow;
end