A novel approach to lossy filter synthesis

In this paper, a novel approach to lossy filter synthesis is presented. First a method is presented to obtain the reflection function once the characteristic polynomials defining the transmission function are specified. This allows to impose arbitrary constraints on the return loss (both in the passband and stopband) leaving unchanged the transmission characteristic. An increase in the order of the final network (with respect to the order of the characteristic polynomials) is required to obtain this result. A synthesis method based on even- and odd-mode decomposition has been then developed which is capable of synthesizing the two-port lossy filter network from the computed polynomials. The novel design approach has been verified through a test filter design; simulations confirm expected results.