Synthesis of N-even order symmetric filters with N transmission zeros by means of source-load cross coupling

Abstract

An improvement to filter synthesis based on a double cross-coupled network is proposed which involves introducing coupling between the input and output ports, i.e. the source and load of the device. Additional coupling allows the designer to obtain N transmission zeros in the case of N-even order symmetric filters. It is therefore possible to achieve all the transmission zeros that an N-order transfer function allows. These zeros may be located on the imaginary axis (/spl plusmn/jw/sub 0/) for high selectivity specifications, on the real axis (/spl plusmn//spl sigma//sub 0/), or in the complex quadrant (CQ) (/spl plusmn//spl sigma//sub 0//spl plusmn/jw/sub 0/) to satisfy equalisation specifications. Filters of different order have been designed to validate the proposed synthesis technique.