A New Approach to the Synthesis of Microwave Lossy Filters

In this paper, we first present a novel synthesis method based on an even- and odd-mode decomposition. This method is capable of synthesizing a network under very general hypotheses and is, therefore, suitable for lossy filter design. To exploit the increased flexibility of this new synthesis method over the traditional lossy design techniques, we then introduce a new approach to the design of lossy filters based on the characteristic polynomials evaluation. This new technique can offer many advantages over traditional techniques, and the main one is that, once the transmission function of the filter is known using traditional methods, the reflection function can be constrained with a certain degree of freedom. A tradeoff between additional constraints and redundancy in the final network must be accepted. Finally, we present design examples and a practical realization, which validate this novel approach to the design of lossy filters.