Communication System, Dual-mode Filter

The more and more congestible frequency spectrum and strait channel require the filters with better performance. In addition, emerging applications such as Integrated Circuits continue to challenge tilters with smaller size. The outside constraint has made filters have smaller area and bulk, with the precondition of higher performance. The dielectric filters and dual-mode filters accord with the above-mentioned conditions. The dual-mode filters have simpler arts and crafts, so they are more convenient for applications relative to the dielectric filters.We analyzed the dual-mode filters with the planar structures in this paper and offered the research course in details. New coupling coefficient formula and I/O coupling coefficient of dual-mode filters are derived also. Seven dual-mode microstrip filters are simulated and designed, two of which are fabricated. The good agreements between the simulated and measured results demonstrate our proposed structures.