A filter device includes first to third resonators. Each of the first to third resonators includes a first line part and a second line part electrically connected to the first line part and having an impedance smaller than an impedance of the first line part. The impedance ratio in at least one of the first to third resonators is 0.3 or smaller. The shape of each of the second line part of the first resonator and the second line part of the second resonator is long in a direction orthogonal to a stacking direction and crossing the longitudinal direction of the second line part of the third resonator.

A filter device includes a dielectric substrate, first and second ground electrodes connected to a ground terminal, and resonators between the ground electrodes and electromagnetically coupled to each other. The ground electrodes are at different positions in a normal direction of the dielectric substrate. Each of the resonators includes a first capacitor electrode partially overlapping with the first ground electrode in plan view of the dielectric substrate, a second capacitor electrode partially overlapping with the second ground electrode in plan view of the dielectric substrate, and a via connecting the capacitor electrodes. The resonators include a first resonator connected to an input terminal, a second resonator connected to an output terminal, and a third resonator between the first and second resonators. Shunt electrodes are connected to the via and the ground terminal in the first and second resonators, respectively.

A filter device includes a stack including a plurality of dielectric layers stacked together, and first to third resonators integrated with the stack. Each of the first to third resonators includes a first conductor part and a second conductor part electrically connected to the first conductor part and having an impedance smaller than an impedance of the first conductor part. The first conductor part and the second conductor part are arranged at positions different from each other in a stacking direction.

A filter comprising a flexible PCB with one or more signal tracks on one side. A electromagnetically absorbing material covers the signal tracks. An insulating material may be provided between the signal tracks and the electromagnetically absorbing material. The PCB is then folded or rolled to take up less space. The PCB may be first folded and then rolled to have both ends of the signal tracks available at the outer portion of the roll.

A filter device includes a multilayer substrate, an inductor, and a first open stub. The multilayer substrate includes a first wiring layer, a second wiring layer including a first reference electrode to which a reference potential is supplied, and a plurality of first dielectric layers between the first wiring layer and the second wiring layer. The inductor has one end coupled to a first terminal and another end coupled to a second terminal. A portion of the first open stub is provided in the first wiring layer, and the first open stub has one end coupled to the one end of the inductor and another open-circuited end. When the multilayer substrate is viewed in plan view in a stacking direction, a capacitor is formed by the first reference electrode and the first open stub that mutually overlap. A resonant circuit is formed by the capacitor and the inductor.

A multi-layered resonator circuit structure and a multi-layered filter circuit structure. The multi-layered resonator circuit structure includes a multi-layered substrate, a plurality of resonators and a plurality of conductive components. The multi-layered substrate has a top surface, a bottom surface, and a ground layer. The top surface and the bottom surface face away from each other. The ground layer is located between the top surface and the bottom surface. A part of the plurality of resonators is/are disposed on the top surface. Another part of the plurality of resonators is/are disposed on the bottom surface. The plurality of conductive components is located in the multi-layered substrate. The plurality of resonators is electrically connected to the ground layer, respectively, via the plurality of conductive components.

A filter device includes a laminate body, plate electrodes, resonators, and shield conductors. The plate electrodes are provided in the laminate body and are spaced apart from each other in a lamination direction. The resonators are between the plate electrodes and extend in a first direction. The shield conductors are on respective side surfaces of the laminate body, and connected to the plate electrodes. The resonators are within the laminate body and aligned in a second direction. The resonators each include a first end connected to the shield conductor and a second end spaced apart from the shield conductor. The resonator includes conductors laminated in the lamination direction. When the resonator is viewed in plan from the first direction, the conductors each include a first region including an end portion of the conductor and having a thickness greater than other portions of the conductor.

A multi-layer waveguide comprising at least three physical layers assembled into a multi-layer waveguide. The layers are a top layer, one or more intermediate layer, and a bottom layer. The multi-layer waveguide further comprises a waveguide channel being an elongated aperture in at least one intermediate layer. At least one layer has a metasurface on a first surface facing a first adjoining layer, wherein the metasurface surrounds the elongated aperture and comprise thick and thin sections.

In a resonant device, a third plane electrode is located between a first plane electrode and a second plane electrode. A first via electrode connects the first plane electrode and the third plane electrode. A second via electrode, a third via electrode, and a fourth via electrode connect the first plane electrode and the second plane electrode. When the third plane electrode is seen in plan view in a normal direction of the first plane electrode, the third plane electrode includes a first projecting portion overlapping with a first area between the second via electrode and the third via electrode, and a second projecting portion overlapping with a second area between the third via electrode and the fourth via electrode.

In a resonant device, a first via electrode and a second via electrode connect a first plane electrode and a third plane electrode. A third via electrode and a fourth via electrode connect the first plane electrode and a second plane electrode. When the first plane electrode is seen in plan view in a normal direction of the first plane electrode, a first imaginary line connecting the first via electrode and the second via electrode intersects with a second imaginary line connecting the third via electrode and the fourth via electrode.