Synthesis of dual-band filters with parallel-connected networks

We discuss in this work a novel approach to the synthesis of dual-band filters having a parallel-connected topology. The only existing synthesis technique for this class of filters offers a very limited control over the topology of the two constituting filters. The approach we propose allows to control the number of transmission zeros of each filter connected in parallel, making the realization of the overall dual-band filter more convenient from a practical point of view. The solution of the problem is based on the introduction of additional transmission zeros which are obtained by means of an iterative procedure. Two examples illustrate the effectiveness of the proposed approach in case of symmetrical and asymmetrical response of the dual-band filter.