Dual-Band Bandpass Filter With Controllable Bandwidths Using Two Coupling Paths

This letter presents the designs of dual-band bandpass filters using two coupling paths to control the bandwidth of each passband. One coupling path only delivers signals at the upper passband frequency whereas the other one couple signals at both passbands. Utilizing this method, the two bandwidths can be adjusted. The filters make use of stub-loaded resonators and it is convenient to tune the passband frequencies. Therefore, both the frequency and bandwidth of each passband can be easily controlled. For demonstration purpose, two example filters are implemented with different bandwidths. The experimental results are presented to verify the proposed method.