Synthesis of capacitive-coupled dual-behavior resonator (CCDBR) filters

The two topologies and associated syntheses described here are dedicated to the design of capacitive-coupled dual-behavior resonator filters. The technique is based on the coupling of adjacent dual-behavior resonators (DBRs). The aim is to control the spurious resonances associated to classical DBR filters. In the first coupling technique, the inverter is replaced with an equivalent scheme composed of a set of three capacitors, i.e., a positive capacitor associated with two negative ones in parallel on both sides. The second technique relies on the same principle, but two equivalent schemes are moved along each stub of the resonators; the capacitance is then calculated by considering the position of the coupling effect on the stub and the value of the inverter. In both cases the synthesis is totally defined. In order to validate this concept, capacitive-coupled DBR filters and classical filters were designed on alumina substrate so as to compare simulation and experimental data