A method for creating multiple attenuation poles by a microwave filter based on tapped resonators

According to the improvement of out-of-passband characteristics for microwave filters, a method for creating multiple attenuation poles is proposed by a tapped bandpass filter (BPF) based on the combination of basic resonators. In this paper, we present new BPFs on the basis of the combination of three types of basic resonators. As a result, multiple attenuation poles are easily obtained by the tapped BPF. This study lead us to the conclusion that the tapped BPF based on our concept is very useful for improving out-of-passband characteristics