A first switch is configured to open and close connection between an end part of a first transmission line and ground, and a second switch is configured to open and close connection between an end part of a third transmission line and ground.

A high-frequency circuit includes: a first ground layer having an electric conductor formed therein; a second ground layer having an electric conductor formed therein; and a conductive pattern layer having a first conductive pattern formed thereon. The first ground layer, the second ground layer, and the conductive pattern layer are laminated one on another. The conductive pattern layer includes a first area in which a distance to the electric conductor formed in the second ground layer is longer than a distance to the electric conductor formed in the first ground layer, in a lamination direction in which the first ground layer, the second ground layer, and the conductive pattern layer are laminated. At least a part of the first conductive pattern is disposed in the first area.

A bandstop filter includes a coupled line bandstop filter, a capacitor and a resistor. The coupled line bandstop filter includes a transmission line element and a shaped transmission line element. The shaped transmission line element includes a coupled line element disposed so as to electromagnetically couple with the transmission line element, and a second line element disposed so as not to be parallel with the transmission line element. The capacitor is electrically connected to the coupled line element. A portion of the received oscillating signal includes a bandstop frequency. Physical attributes of the coupled line bandstop filter, the capacitor and the resistor are such that the portion of the received oscillating signal including the bandstop frequency is attenuated.

A filter for electromagnetic noise comprising: a printed circuit board (5) having conductor tracks, having a first side and having a second side opposite the first side; a first busbar (1), which is secured on the first side of the printed circuit board (5) and is electrically connected to at least one of the conductor tracks; and a second busbar (2), which is secured on the second side of the printed circuit board (5) and is electrically connected to at least one of the conductor tracks. The printed circuit board (5) is arranged between the first busbar (1) and the second busbar (2) for the insulation thereof.

A distributed electromagnetic (EM) wave filter includes: a cavity; upper and lower ground planes on top and bottom surfaces of the cavity, wherein the upper and lower ground planes are in electrical contact; a plurality of electromagnetically coupled resonators in said cavity between the upper and lower ground planes that define respective transmission lines, wherein the plurality of resonators are not connected to each other by a conductive connection; an input port coupled to a first one of the plurality of resonators to receive an EM wave; an output port coupled to a last one of the plurality of resonators to output a filtered EM wave; and a plurality of conductive structures between adjacent resonators, respectively and connected to one or more of the upper and lower ground planes.

Multi-pair differential lines printed circuit board common mode filters are generally described. In one embodiment, the apparatus includes a multi-layer printed circuit board, a first signal line and a second signal line forming a first differential pair on a first layer of the printed circuit board, a second differential pair on the first layer of the printed circuit board, and a common mode filter on a second layer of the printed circuit board, the common mode filter comprising an absence of a predominantly occurring dielectric material of the printed circuit board, the common mode filter spanning an area directly below at least a portion of both the first and the second differential pairs. Other embodiments are also described and claimed.

A three-dimensional (3D) filter and a fabrication method thereof are provided. The 3D filter includes a circuit board, a first ring resonator, a second ring resonator and a via structure. The circuit board includes a first circuit layer, a second circuit layer and a third circuit layer. The third circuit layer is located between the first circuit board and the second circuit board. The first ring resonator is disposed in the first circuit layer and has a first ring surrounded area corresponding to a first cut-off frequency band. The second ring resonator is disposed in the second circuit layer and has a second ring surrounded area corresponding to a second cut-off frequency band. The via structure passes through the first circuit layer, the second circuit layer and the third circuit layer, and is electrically connected to the first ring resonator and the second ring resonator.

A filter comprises: a plurality of resonators, each of which is provided with a via electrode and capacitor electrodes; a first shielding conductor; and a first coupling capacitance electrode that faces the first shield conductor and is not connected to any of the plurality of resonators. The first coupling capacitance electrode is formed on a layer on which a first capacitor electrode is formed, and a part of the first coupling capacitance electrode is positioned between a second capacitor electrode and the first shield conductor.

An electronic filter includes a ground plane and a top conductor overlying the ground plane. The top conductor includes an input and an output for receiving and outputting signals, respectively. The filter further includes a plurality of unit cells arranged in series along the top conductor. Each of the plurality of unit cells includes a planar structure disposed between the top conductor and the ground plane. Each of the plurality of unit cells further includes a pair of vias connecting the planar structure to the ground plane.