Signal Toolkit - isallpass

Function File: L = isallpass (b, a)

Function File: L = isallpass (sos)

Determine whether a digital filter is allpass. The filter might be defined by the numerator coefficients, b, and the denominator coefficients, a, or, alternatively, by a matrix of second-order sections, sos.

Example:

 a = [1 2 3];
 b = [3 2 1];
 isallpass (b, a)
 

Ref [1] Shyu, Jong-Jy, & Pei, Soo-Chang, A new approach to the design of complex all-pass IIR digital filters, Signal Processing, 40(2–3), 207–215, 1994. https://doi.org/10.1016/0165-1684(94)90068-x

Ref [2] Vaidyanathan, P. P. Multirate Systems and Filter Banks. 1st edition, Pearson College Div, 1992.