Design of microstrip bandstop filter with adjustable wide passband using folded open-circuited stub resonators

This paper presents a new class of microstrip bandstop resonator filters. The folded open-circuited stub resonator located into microstrip loop structure is investigated using full-wave electromagnetic simulations. The utilization of the novel stub resonator allows a compact bandstop filter configuration to be realized. The proposed filter not only has a compact size, but also has a wider upper passband. Both simulated and measured results are presented to demonstrate the proposed filter.