sdir2cas.m

the file contain many matlab signal source code and many example .

function [C,B,A]=sdir2cas(b,a)
% DIRECT - form to CASCADE - form conversion in s-plane
% ----------------------
% [C,B,A]=sdir2cas(b,a)
% C=gain coefficient
% B=K by 3 matrix of real coefficients containing bk's
% A=K by 3 matrix of real coefficients containing ak's
% b=numberator polynomial coefficients of DIRECT form
% a=denominator polynomial coefficients of DIRECT form
%
Na=length(a)-1;Nb=length(b)-1;
% compute gain coefficient C
b0=b(1);b=b/b0;
a0=a(1);a=a/a0;
C=b0/a0;
%
% Denominator second-order sections:
p=cplxpair(roots(a));K=floor(Na/2);
if K*2==Na     % Computation when Na is even 
    A=zeros(K,3);
    for n=1:2:Na
        Arow=p(n:1:n+1,:);
        Arow=poly(Arow);
        A(fix((n+1)./2),:)=real(Arow);
    end
elseif Na==1     % Computation when Na=1
    A=[0 real(poly(p))];
else             % Computation when Na is odd and >1
    A=zeros(K+1,3);
    for n=1:2:2*K
        Arow=p(n:1:n+1,:);
        Arow=poly(Arow);
        A(fix((n+1)./2),:)=real(Arow);
    end
    A(K+1,:)=[0 real(poly(p(Na)))];
end 
% Numerator second -order sections:
z=cplxpair(roots(b));K=floor(Nb/2);
if Nb==0    % Computation when Nb=0
    B=[0 0 poly(z)];
elseif K*2==Nb  % Computation when Nb is even 
    B=zeros(K,3);
    for n=1:2:Nb
        Brow=z(n:1:n+1,:)
        Brow=poly(Brow);
        B(fix((n+1)./2),:)=real(Brow);
    end
elseif Nb==1    % Computation when Nb=1
    B=[0 real(poly(z))];
else         % Computation when Nb is odd and >1
    B=zeros(K+1,3);
    for n=1:2:2*K
        Brow=z(n:1:n+1,:)
        Brow=poly(Brow);
        B(fix((n+1)./2),:)=real(Brow);
    end
    B(K+1,:)=[0 real(poly(z(Nb)))];
end