Small‐size high‐selectivity bandstop filter with coupled‐line stubs for dual‐band applications

A novel coupled‐line stub is proposed for the design of a novel dual‐band small‐size bandstop filter (BSF). This kind of coupled‐line dual‐band BSF features a compact and simple structure, flexible frequency‐ratio adjustment and high selectivity. To verify the proposed circuit structure and design approach, a microstrip example has been fabricated and measured. The measured results show a good agreement with the simulated responses.