A balun includes a first capacitor, a second capacitor, a first inductor, an unbalanced signal port, a first balanced signal port, and a second balanced signal port. The first capacitor and the second capacitor are electrically connected in series between the unbalanced signal port and the first balanced signal port. The first inductor is electrically connected in parallel to the first capacitor and the second capacitor electrically connected in series. A second signal path is electrically connected to a first signal path between the first capacitor and the second capacitor, and the second balanced signal port is electrically connected to the second signal path.

A variable-frequency LC filter (1A) includes a multilayer circuit board, a series arm capacitor (11) formed in the multilayer circuit board and disposed in a series arm path that connects an input electrode to an output electrode, and a parallel arm inductor (21) formed in the multilayer circuit board and disposed in a parallel arm path that connects a ground electrode to a node (N1) in the series arm path. When the multilayer circuit board is viewed in plan, of the series arm capacitor (11) and the parallel arm inductor (21), only the parallel arm inductor (21) overlaps with the ground electrode.

A filter element is mounted on a module substrate. The filter element includes a ground terminal and a pair of signal terminals. The module substrate includes a ground plane, a ground land, and an inductance adjusting line that connects the ground land to the ground plane. The ground terminal of the filter element is connected to the ground land of the module substrate. The inductance adjusting line includes an in-plane extending portion that extends in an in-plane direction of the module substrate.

A filter device is mounted on a module substrate and is shielded by a shield member. The filter device has first and second side surfaces opposed to each other. A ground terminal and signal terminals are formed on a bottom surface of the filter device. The shield member includes side wall portions facing the first and second side surfaces. The filter device includes plural LC parallel resonance circuits therein. The inductors of the LC parallel resonance circuits are arranged in parallel with the first side surface and the bottom surface. Each inductor extends upward from its end portion electrically connected to the ground terminal, extends from the first side surface toward the second side surface, and then extends toward the bottom surface. The gap between the first side surface and the corresponding side wall portion is smaller than that between the second side surface and the corresponding side wall portion.

The present invention is directed to communication systems and electrical circuits. More specifically, an embodiment of the present invention provides a termination circuit that includes a programmable gain attenuation section, a T-coil section, and a termination resistor. The characteristic resistance of the programmable gain attenuation section matches the resistance of the termination resistor. There are other embodiments as well.

A multilayer body includes a first inductor and a second inductor provided in a first planar region, and a third inductor and a fourth inductor provided in a second planar region when viewed in a lamination direction of dielectric layers of the multilayer body. When the multilayer body is viewed in a direction perpendicular or substantially perpendicular to the lamination direction of the dielectric layers, the first inductor and the fourth inductor are provided in a first thickness region, and the second inductor and the third inductor are provided in a second thickness region.

A multilayer LC filter includes one via conductor on a second edge side and two via conductors on a fourth edge side that are connected to line-shaped conductor patterns of a first inductor, and two via conductors on the second edge side and one via conductor on the fourth edge side that are connected to line-shaped conductor patterns of a second inductor, and the third to fifth inductors also have this same relationship.

Aspects of this disclosure relate to a band pass filter that includes LC resonant circuits coupled to each other by a capacitor. A bridge capacitor can be in parallel with series capacitors, in which the series capacitors include the capacitor coupled between the LC resonant circuits. The bridge capacitor can create a transmission zero at a frequency below the passband of the band pass filter. The LC resonant circuits can each include a surface mount capacitor and a conductive trace of the substrate, and an integrated passive device die can include the capacitor. Band pass filters disclosed herein can be relatively compact, provide relatively good out-of-band rejection, and relatively low loss.

A filter includes: first and second parallel resonant circuits including a first capacitor, a first line, a second capacitor, and a second line that are shunt-connected to a series pathway connecting the input and output terminals; and first to sixth vias penetrating through a second dielectric layer on which the first and second lines are disposed, the first via connecting the first line to the series pathway, the second via connecting the first line to the ground terminal, the third via connecting the first line at a position between the first and second vias to the first connection line at a first position, the fourth via connecting the second line to the series pathway, the fifth via connecting the second line to the ground terminal, the sixth via connecting the second line at a position between the fourth and fifth vias to the first connection line at a second position.

A multilayer LC filter includes a magnetic coupling adjustment inductor for at least one LC resonator. The magnetic coupling adjustment inductor includes a line conductor pattern and a first via conductor connected to each other. The line conductor pattern is connected to an intermediate point of a second via conductor, and the first via conductor is connected to a ground conductor pattern. A loop inductor and the magnetic coupling adjustment inductor in the LC resonator for which the magnetic coupling adjustment inductor is provided are magnetically coupled to a loop inductor in another adjacent LC resonator.