《DSP using MATLAB 》示例Example6.3

  

代码：

C0 = 0; B1 = [2 4; 3 1]; A1 = [1 1 0.9; 1 0.4 -0.4];
B2 = [0.5 0.7; 1.5 2.5; 0.8 1]; A2 = [1 -1 0.8; 1 0.5 0.5; 1 0 -0.5];
[b1, a1] = par2dir(C0, B1, A1)[b2, a2] = par2dir(C0, B2, A2)b = conv(b1, b2)      % Overall direct form numerator
a = conv(a1, a2)      % Overall direct form denominator[b0, Bc, Ac] = dir2cas(b, a)     % Overall cascade form[C0, Bp, Ap] = dir2par(b, a)     % Overall parallel form

　　运行结果：

根据系数写出相应的公式：