Design of PCAS structures to meet arbitrary specifications using a phase design technique

The parallel combination of allpass subfilters (PCAS) is a highly efficient filter structure suitable for use in high performance filtering applications. The structure has been widely applied to the design of filters to meet stringent specifications in terms of magnitude and phase, or group delay. This paper presents a design method, for these types of specifications, that formulates the design purely in terms of the filter phase. This leads to an efficient, reliable design method. Comparison is made between this and previously published design methods