Design of doubly complementary filters based on the complex all-pass section

A new procedure for the design of a real Doubly Complementary (DC) pair of digital filters obtained from an all-pass structure is presented. The filter design is based on a zero-phase FIR filter design with multi-band frequency specifications and approximate linear-phase characteristic. The resulting complex all-pass filter structure is guaranteed to be stable. An example illustrating the design method is also shown.