An LC filter includes a multilayer body including dielectric layers layered therein, plate electrodes, capacitor electrodes, inductor vias, and ground vias. The plate electrodes are provided on different layers of the multilayer body. The capacitor electrodes each define a capacitor between itself and the electrode. The inductor via is connected with the electrode and the capacitor electrode, while the inductor via is connected with the electrode and the capacitor electrode. The ground vias connect the plate electrodes to each other. The inductor via and the capacitor electrode define a resonance circuit that receives a signal from an input terminal. The inductor via and the capacitor electrode define a resonance circuit that transfers a signal to the output terminal.

An LC filter includes a multilayer body, plate electrodes, capacitor electrodes, and inductor vias. The capacitor electrodes each define a capacitor between the plate electrode and a corresponding one of the capacitor electrodes. A first inductor via is connected between a first capacitor electrode and a first plate electrode. A second inductor via is connected between a second capacitor electrode and the first plate electrode. A third inductor via is connected between a third capacitor electrode and the first plate electrode. A fourth capacitor electrode faces the first and second capacitor electrodes. A fifth capacitor electrode faces the second and third capacitor electrodes. A sixth capacitor electrode faces the first and third capacitor electrodes.

Radio frequency filtering circuitry blocks certain frequencies in an outgoing signal so that the signal may be transmitted over a desired frequency. The radio frequency filtering circuitry includes a first inductor having a first coil and a second inductor coupled to and disposed within the first coil. The second inductor has a second coil and a third coil symmetrical to the second coil. When current is applied to the radio frequency filtering circuitry, the current in the second coil causes a first induced current in the first coil and the current in the third coil causes a second induced current in the first coil, wherein the second induced current is approximately equal in magnitude and opposite in direction to the first induced current. As such, the second induced current may compensate for the first induced current.

An apparatus, as an electromagnetic wave back introduction blocking module connected between an ignition (IG) system and a converter, includes a front capacitor module which includes a first coil part including one or more coils having one side connected to the IG system in series and a first capacitor part connected between the other side of the first coil part and a ground, a central coil module which includes a second coil part including one or more coils having one side connected to the other side of the first coil part and a second capacitor part connected between the other side of the second coil part and the ground, and a rear capacitor module which includes a third capacitor part having one side connected to the other side of the second coil part. The rear capacitor module is connected to the converter.

A band antenna EMP filter apparatus having HEMP protection capability is disclosed. The apparatus includes a discharging part, a band pass filtering part, and a residual current eliminating part. The discharging part primarily discharges a transient voltage due to a high altitude electromagnetic pulse (HEMP) when the HEMP is inputted through an input part receiving a radio frequency (RF) signal of an antenna. The band pass filtering part secondarily blocks a residual current primarily discharged by the discharging part and passes only a signal of a preset frequency band to output it through an output part. The residual current eliminating part limits a transient voltage of the HEMP by eliminating a residual current passing through the band pass filtering part.

A bias circuit includes first to fourth transistors and a phase compensation circuit. In the first transistor, a reference current or voltage is supplied to a first terminal, and the first terminal and a second terminal are connected. In the second transistor, a first terminal is connected to the first transistor, and a third terminal is grounded. In the third transistor, a power supply voltage is supplied to a first terminal, a second terminal is connected to the first transistor, and a bias current or voltage is supplied from a third terminal to an amplifier transistor. In the fourth transistor, a first terminal is connected to the third transistor, a second terminal is connected to the second transistor, and a third terminal is grounded. The phase compensation circuit is provided in a path extending from the fourth transistor to the third transistor through the second and first transistors.

An integrated passive die includes a substrate, an input node, an output node, and RF filtering circuitry. The RF filtering circuitry includes a number of LC tank circuits coupled between the input node and the output node. Each one of the LC tank circuits include an inductor and a capacitor. The inductor is formed by a metal trace over the substrate. The capacitor is coupled in parallel with the inductor over the substrate. The inductor and the capacitor are provided such that a resonance frequency of the combination of the inductor and the capacitor is less than a self-resonance frequency of the inductor.

A filter circuit including a plurality of capacitances and a plurality of inductances including one variable reactance that is either an inductance or a capacitance. The filter circuit has a plurality of resonant modes that each correspond to resonance at a resonant frequency between the variable reactance and one or more of the plurality of inductances and one or more of the plurality of capacitances. The variable reactance is conductively coupled with one or more other inductances and capacitances of the pluralities of inductances and capacitances such that a change in the variable reactance causes a change in a resonant frequency of more than one of the plurality of resonant modes. Front-end modules and wireless communication devices incorporating such a filter circuit and a method using such a filter circuit are also described.

A circuit board having excellent reliability of connection between layers while being capable of achieving a compact and low-profile electronic device. In the circuit board has an LC circuit built therein with the use of a glass core having a through hole, a conductor layer formed in the through hole is connected to a wiring pattern formed on one surface of the glass core, and connected to a wiring pattern formed on the other surface of the glass core, with the conduction layer projected from the surface of the glass core. Thus, the area of contact between the conduction layer and the through hole is increased, thus making it possible to prevent the reliability of connection between layers in the through hole from being decreased, even when the glass core is reduced in thickness for achieving a low-profile device.

The integrated circuit includes a power amplifier, an antenna, and a matching and filtering network including a direct current power supply stage on an output node of the power amplifier, a first section, and a second section. The direct current power supply stage and the two sections include inductor-capacitor “LC” arrangements configured to have an impedance that is matched to the output of the power amplifier in the fundamental frequency band. The LC arrangements of the direct current power supply stage and of the first section are furthermore configured to have resonant frequencies that are respectively adapted to attenuate harmonic frequency bands of the fundamental frequency band.