Abstract: A filter structure improvement includes a substrate, resonance layers, a grounded layer, a pattern layer, an input electrode, and an output electrode. The substrate has resonance holes in which the resonance layers are disposed. One end of the resonance hole is on the open surface and the other end of the resonance hole is on the short-circuit surface. The grounded layer is on the short-circuit surface, top surface, bottom surface, and side surfaces and is electrically connected to the resonance layers to form a short-circuit end. The input and output electrodes, electrically isolated from the grounded layer, are on the bottom or open surface of the substrate. The pattern layer, resonance layers, and grounded layer are arranged to have electrical properties of a filter structure of mutual coupling such that a desired frequency band is obtained by adjusting the pattern layer and the lengths of the resonance layers.

Abstract: A filter structure improvement includes a substrate, resonance layers, a grounded layer, a pattern layer, an input electrode, and an output electrode. The substrate has resonance holes in which the resonance layers are disposed. One end of the resonance hole is on the open surface and the other end of the resonance hole is on the short-circuit surface. The grounded layer is on the short-circuit surface, top surface, bottom surface, and side surfaces and is electrically connected to the resonance layers to form a short-circuit end. The input and output electrodes, electrically isolated from the grounded layer, are on the bottom or open surface of the substrate. The pattern layer, resonance layers, and grounded layer are arranged to have electrical properties of a filter structure of mutual coupling such that a desired frequency band is obtained by adjusting the pattern layer and the lengths of the resonance layers.