function [b,a] = cas2dir(b0,B,A);
% 級(jí)聯(lián)型到直接型的型式轉(zhuǎn)換
% ---------------------------------
% [b,a] = cas2dir(b0,B,A)
%  b = 直接型的分子多項(xiàng)式系數(shù)
%  a = 直接型的分母多項(xiàng)式系數(shù)
% b0 = 增益系數(shù)
%  B = 包含各bk的K乘3維實(shí)系數(shù)矩陣
%  A = 包含各ak的K乘3維實(shí)系數(shù)矩陣
%
[K,L] = size(B);
b = [1];
a = [1];
for i=1:1:K
	b=conv(b,B(i,:));
	a=conv(a,A(i,:));
end
b = b*b0;