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.