Research On Miniaturized Filters Based On Novel Resonant Structures

The microwave devices in the modern communication system should meet the needs of miniaturization, light height and high level of compactness. Since the resonant structure has a smaller electrical size, the prospects to realize miniaturization are broad. In order to realize the miniaturization of microwave circuits, some new structures are proposed in this paper. A novel split-ring resonator(SRR), which is etched on the back side of a coplanar waveguide(CPW), is presented and discussed. Metallic vias are used to connect the novel SRR to ground planes of CPW, which greatly enhance the resonance of the structure. A stop band filter and a pass band filter based on this novel structure are simulated and fabricated. Simulated and measured results are in good agreement. According to the concept of duality, the dual structure of the novel SRR, which has wider bandwidth than traditional structures, is etched on the surface of a substrate integrated waveguide(SIW). This filter can work below the cutoff frequency of SIW. The frequency selectivity of this SIW filter is improved due to the existence of a pair of transmission zeros outside the pass band. A band pass SIW filter cascading two novel complementary split-ring resonators(CSRR), is realized and measured. All of the proposed filters have the advantages of high level of compactness.