Two simple implementations of transversal filters with coupling between non-resonant nodes

This paper introduces two novel configurations, both with the same circuit topology, for the synthesis of pseudo-elliptic microwave filter responses. The structures are of second order, and implement two transmission zeros and two reflection zeros in the frequency response of the filter. The basic structure consists on input and output ports coupled, in a shunt configuration, to two resonators of different lengths, and presents also an additional coupling between the source and the load. Depending on the sign of this last coupling, dual frequency responses can be obtained. In this paper two possible microstrip implementations of passband of stopband filters are proposed, following this circuit topology. A manufactured prototype is presented. Measured results confirm the theoretical predictions, and validate the novel structures for high selectivity applications.