A variable-frequency LC filter that has sharp attenuation characteristics and that does not increase the size of a substrate and a high-frequency frontend module using such a variable-frequency LC filter are provided. A first variable capacitor and a second variable capacitor are disposed on a principal surface such that strength of magnetic field coupling caused between a first inductor and a third inductor is greater than strength of magnetic field coupling caused between a second inductor and the first inductor and than strength of magnetic field coupling caused between the second inductor and the third inductor.

An LC resonator includes a laminate body including dielectric layers that are laminated in a lamination direction. The LC resonator includes a first capacitor, a second capacitor, and an inductor connected between the first capacitor and the second capacitor. A first end of the inductor is isolated in a direct current from a ground node by the first capacitor. A second end of the inductor is isolated in a direct current from the ground node by the second capacitor.

The present disclosure provides a variable filter circuit capable of controlling a band width and a center frequency of a pass band, and also capable of suppressing the total number of pieces of variable reactance. That is, a variable filter circuit includes a serial arm in which a plurality of circuit elements are connected in series with respect to a signal path and a parallel arm in which a plurality of circuit elements are connected in parallel with respect to the signal path, wherein the serial arm and the parallel arm each includes a variable reactance element, a series reactance element that is connected in series to the variable reactance element and resonates therewith, and a parallel reactance element that is connected in parallel to the variable reactance element and resonates therewith.

The present disclosure includes a first circuit that is connected between a power feed port and an antenna port, and a second circuit that is connected between the power feed port and the ground or between the antenna port and the ground. The first circuit is a circuit in which for example a first variable capacitance element is connected in series with a first inductor, and the second circuit is a circuit in which for example a second variable capacitance element is connected in parallel with a second inductor. A switch performs switching at least between a first state in which a second end of the second circuit is connected to a first end of the first circuit and a second state in which the second end of the second circuit is connected to a second end of the first circuit.

A multilayer LC filter includes a multilayer body in which dielectric layers are laminated, first linear conductive patterns, second linear conductive patterns, third linear conductive patterns, capacitor conductive patterns, ground conductive patterns, and via conductors. When the multilayer body is seen through in the direction in which the dielectric layers are laminated, the first linear conductive patterns and the third linear conductive patterns in a first inductor intersect with each other, and the first linear conductive patterns and the third linear conductive patterns in a second inductor intersect with each other.

Embodiments of the present invention provide an inductively coupled filter and a WiFi module. The inductively coupled filter includes a first circuit, where the first circuit is disposed on a first substrate; and a second circuit, where the second circuit is disposed on a second substrate; and the first substrate and the second substrate are disposed opposite to each other, so that a coil inductor in the first circuit and a coil inductor in the second circuit form a mutual induction structure. In the inductively coupled filter in the embodiments of the present invention, the coil inductors are disposed on two substrates respectively. This can reduce an area occupied by the inductively coupled filter on each package substrate.

Radio frequency (RF) filters configured to filter undesired signal components (e.g., noise and harmonics) from RF signals are disclosed. In one embodiment, an RF filter includes a first inductor coil having a first winding and a second inductor coil having a second winding and a third winding. The second winding of the second inductor coil is configured to have a first mutual magnetic coupling with the first winding, while the third winding of the second inductor coil is configured to have a second mutual magnetic coupling with the first winding. The second winding is connected to the third winding such that the first mutual magnetic coupling and the second mutual magnetic coupling are in opposition. In this manner, the first inductor coil and the second inductor coil may be provided in a compact arrangement while providing weak mutual magnetic coupling between the first inductor coil and the second inductor coil.

Embodiments of radio frequency (RF) filtering circuitry are disclosed. In one embodiment, the RF filtering circuitry includes a first port, a second port, a first RF filter path, and a second RF filter path. The first RF filter path is connected between the first port and the second port and includes at least a pair of weakly coupled resonators. The weakly coupled resonators are configured such that a first transfer response between the first port and the second port defines a first passband. The second RF filter path is coupled to the first RF filter path and is configured such that the first transfer response between the first port and the second port defines a stopband adjacent to the first passband without substantially increasing ripple variation of the first passband defined by the first transfer response.

An LC filter includes first and second LC resonators including first and second inductors, respectively. In plan view from a winding axis direction of the first inductor, an air-core portion of the first inductor does not coincide with an air-core portion of the second inductor. The LC filter includes a bypass conductor that connects an intermediate portion of the first inductor between one end and another end of the first inductor and an intermediate portion of the second inductor between one end and another end of the second inductor.

The invention relates to a method for controlling a converter connected to an electric machine by a cable (Cx) via a filter (F), said method consisting in determining at least one sequence of a plurality of voltage pulses forming a square wave signal to be applied to each conductor so as to minimize an overvoltage level, said sequence comprising a number 2N of successive pulses, N being greater than or equal to 1, each pulse being defined by a distinct rank n, said sequence being generated such that each increasing voltage pulse of rank n exhibits a pulse width that is identical to that of a decreasing voltage pulse of rank equal to 2N+1n, and the method includes the following steps in particular: determining the number of successive pulses of said sequence; determining the width of each pulse of the sequence made suitable for minimizing the overvoltage level across the terminals of the electric machine (M).