Dual-band microstrip bandpass filter with independently-tunable passbands using patch resonator
A novel dual-band bandpass filter using patch resonator combined with microstrip resonant stubs is proposed. Two crossed slots are introduced to disturb the TE200 mode and TE002 mode of patch resonator, forming the first passband (low frequency). Two orthogonal microstrip stubs bring the source–load coupling while they also work as resonators, providing the second passband (high frequency). Each passband can be tuned independently due to the independent-resonant paths and non-crossed couplings between working modes. The proposed filter shares a simple layout, and three transmission zeros are obtained and it results in good selectivity and good out-band rejection. The measured results agree with simulated results well.