High-Q Substrate Integrated Waveguide Resonator Filter With Dielectric Loading

A planar cavity is proposed, designed, and implemented with a hybrid substrate integrated waveguide (SIW) and periodically drilled SIW (PDSIW) structure. Air holes are added to synthesize a lower effective permittivity. The periodicity can increase the stored energy and improve the quality factor. The optimal ratio between the two permittivities is investigated. The measured results show that the proposed resonator has an unloaded quality factor (Qu) of 815, which is 53% higher than its standard SIW counterpart. To demonstrate the potential of the proposed PDSIW cavity, a third-order filter is designed and implemented through the proposed cavity, and it is then compared with filters of different orders. The new filter with a cavity shows performance enhancements in terms of both loss and bandwidth. The SIW resonator can be a promising element for use in the design of high-performance microwave filters and oscillators.