Miniaturized wide stopband bandpass filter using in-resonator stub

This paper proposes a novel in-resonator stub technology on designing wide stopband bandpass filter with miniaturized size. The open stubs are directly embedded in the tapped resonator to eliminate the spurs in the stopband without additional circuit occupying or complicated process. On having the wide stopband character, without obviously interfering with the resonance character of the embedded resonator, the design complexity and flexibility of the filter using in-resonator stub is not significantly affected comparing with classical filter design. A series of miniaturized wide stopband bandpass filters using in-resonator stub are designed, fabricated, and measured.