Novel dual-band bandpass filter using multi-mode resonator

A novel dual-band bandpass filter using a multi-mode resonator is presented in this paper. Two passbands for WLAN bands are realized based on a multi-mode resonator with three open stubs. By appropriately selecting the characteristic impedance of the multi-mode resonator, the bandwidth of the two-order passband with even/odd-modes can be adjusted. In addition, the even/odd-modes frequencies can be controlled by the characteristic impedance of the multi-mode resonator, independently. A planar dual-wideband bandpass filter prototype with 3-dB fractional bandwidths 22.8% and 10.6% is designed and fabricated. Good agreement between the simulated and measured results can be observed.