Filter Design Toolbox

iirpowcomp

Compute power complementary filter.

Syntax

• [bp,ap] = iirpowcomp(b,a)
  [bp,ap,c] = iirpowcomp(b,a)
  

Description

[bp,ap] = iirpowcomp(b,a) returns the coefficients of the power complementary IIR filter g(z) = bp(z)/ap(z) in vectors bp and ap, given the coefficients of the IIR filter h(z) = b(z)/a(z) in vectors b and a. b must be symmetric (Hermitian) or antisymmetric (antihermitian) and of the same length as a. The two power complementary filters satisfy the relation

|H(w)|² + |G(w)|² = 1.

[bp,ap,c] = iirpowcomp(b,a) where c is a complex scalar of magnitude =1, forces bp to satisfy the generalized hermitian property

conj(bp(end:-1:1)) = c*bp.

When c is omitted, it is chosen as follows:

• When b is real, chooses C as 1 or -1, whichever yields bp real
• When b is complex, C defaults to 1

ap is always equal to a.

Examples

• [b,a]=cheby1(10,.5,.4);
  [bp,ap]=iirpowcomp(b,a);
  [h,w,s]=freqz(b,a); [h1,w,s]=freqz(bp,ap);
  s.plot='mag'; s.yunits='sq';freqzplot([h h1],w,s)
  

See Also
tf2ca, tf2cl, ca2tf, cl2tf

iirpeak

iirrateup