Bandstop resonator using electrically coupled open stub for compact wideband bandstop filters

In this paper, a compact wideband bandstop resonator in the form of open stub combination is proposed. The wideband characteristic of the proposed bandstop resonator is due to electrical coupling at the ends of the two open stubs. A stopband is approximately improved by 52% (rejection depth: -20dB) compared with the case that the end of open stub is uncombined. Proposed structure increases the skirt selectivity and elastically controls the frequency bandwidth and rejection depth.