Design of selective linear-phase filters with equiripple amplitude characteristics

A simple numerical technique is described for the construction of a nonminimum phase transfer function with an optimum equiripple passband amplitude response and linear-phase characteristics. The linearphase behavior may be maintained over part of or over the entire passband by varying the number of transmission zeros at infinity. Increasing the number increases the selectivity of the filter at the expense of a deterioration in the phase performance towards the edge of the passband. Synthesis is performed using even- and odd-mode decomposition, and tables of element values are provided with graphical design information to enable the design engineer to choose the correct prototype to meet a given specification.