Miniaturized Dual-Band SIW Filters Using E-Shaped Slotlines With Controllable Center Frequencies

In this letter, a simple method for miniaturized dual-band bandpass filters (BPFs) through E-shaped slotlines has been proposed. The slotlines are etched on the edge sides of the substrate-integrated waveguide (SIW) cavities coupled with magnetic fields of the resonant modes, which makes the proposed cavity operate below its fundamental resonant frequency. Moreover, out-of-band rejection has been improved and the center frequencies of the passbands would be flexibly controlled. To prove the feasibility of the above method, a dual-band BPF based on two SIW cavities operating at 3.6 and 6.4 GHz has been realized. In addition, another dual-frequency filter with only one SIW cavity has been designed, where both the slotlines and the SIW cavity are regarded as resonators. They have been fabricated on a single layer and the test results are in good agreement with the simulations.