A diplexer includes a common terminal, first and second terminals, and first and second filters which are electrically connected to the common terminal. The first filter passes a high frequency signal in a first frequency band. The second filter passes a high frequency signal in a second frequency band higher than the first frequency band. Each filter includes an inductor and a capacitor in a dielectric substrate. The first filter includes a first inductor with one end electrically connected to the common terminal, and a first capacitor electrically connected between another end of the first inductor and a ground. An inductance of the first inductor is smaller than an inductance of another inductor included in the first filter. A frequency of an attenuation pole defined by the first inductor and the first capacitor is higher than a frequency of the second frequency band.

An integrated isolator circuit for isolating receiver and transmitter in a Time-Division Duplex transceiver is disclosed. The integrated isolator circuit comprises a first node, a second node and a third node. The integrated isolator circuit further comprises a first capacitor connected in series with a first switch and connected between the first and second nodes. The integrated isolator circuit further comprises a first inductor connected between the first and second nodes and a second capacitor connected between the second node and the third node. The first switch has an on state and an off state, and the integrated isolator circuit is configured to have a different impedance at a certain operating frequency by controlling the state of the first switch.

Described is an apparatus which comprises: a first transmission path for a first frequency band; a second transmission path for a second frequency band different from the first frequency band; a node common to the first and second transmission paths, the node to be coupled to an antenna; and a transmission-zero circuit coupled to the common node.

A multilayer substrate includes a pair of first capacitor electrodes, a pair of second capacitor electrodes, and a dielectric substrate. Electrodes of the pair of first capacitor electrodes are disposed in dielectric substrate so as to face each other in a thickness direction of the dielectric substrate. Electrodes of the pair of second capacitor electrodes are disposed in the dielectric substrate so as to face each other in the thickness direction. A first element and a second element that are disposed in or on the dielectric substrate, and the pair of second capacitor electrodes, the pair of first capacitor electrodes, and a ground electrode that are disposed in the dielectric substrate are arranged in the stated order in the thickness direction. The pair of second capacitor electrodes at least partially overlaps the pair of first capacitor electrodes when viewed in plan in the thickness direction.

A network interface device includes a passive path between an entry port and a first port. The network interface device also includes an active path between the entry port and a second port. The network interface device also includes a buffer in the active path configured to absorb, attenuate, terminate, or isolate radio-frequency (RF) signals. The network interface device also includes a switching element in the active path configured to cause the RF signals to bypass the buffer when the network interface is in a first state that exists during powered operation of the network interface device, and direct the RF signals to the buffer when the network interface device is in a second state that exists during non-powered operation or faulted operation of the network interface device.

A multilayer substrate includes a dielectric substrate, a pair of capacitor electrodes, and an input/output electrode that is an electrode for input, an electrode for output, or an electrode for input and output. The dielectric substrate has a first main surface and a second main surface that are opposite to each other in a thickness direction of the dielectric substrate. The pair of capacitor electrodes is disposed in the dielectric substrate. Electrodes of the pair of capacitor electrodes face each other in the thickness direction. The input/output electrode is disposed on the second main surface of the dielectric substrate. A capacitor that includes the pair of capacitor electrodes and a portion being part of the dielectric substrate and located between the electrodes of the pair of capacitor electrodes at least partially overlaps the input/output electrode electrically connected to the capacitor.

A frontend module includes a first filter having a passband of a first frequency band, a second filter having a passband of a second frequency band, the second frequency band being higher than the first frequency band, a third filter having a passband of a third frequency band, the third frequency band being higher than the second frequency band, and a sub-filter, connected to the second filter, configured to provide attenuation characteristics for the first frequency band, wherein the second filter comprises a plurality of parallel LC resonance circuits arranged between a ground and different nodes, from among a plurality of nodes between a first terminal and a second terminal, wherein an inductor is connected to a portion of the plurality of parallel LC resonance circuits.

A diplexer having a low band filter and a high band filter is disclosed. The disclosure provides a diplexer having a low band filter and a high band filter for preventing the circuit damage due to an electrostatic discharge in the diplexer itself, and minimizing the signal loss according to addition of an electrostatic discharge prevention circuit.

A SAW filter with an antenna and a transmission terminal includes: a plurality of series resonator groups which are connected in series between the antenna and the transmission terminal; a plurality of parallel resonator groups which are connected in parallel between two neighbor series resonator groups among the plurality of series resonator groups; a parallel inductor which is connected in parallel with the series resonator group adjacent to the antenna; and a series inductor which is connected to in series with some parallel resonator groups among the plurality of parallel resonator groups. The SAW filter has high durability in which even though high power is applied to the filter together with the wide pass band, the filter is not damaged.

A radio frequency circuit includes a filter of a Band A, a filter of a Band B, a filter of a Band C, a low pass filter that is connected between a common terminal and a first terminal, a high pass filter that is connected between the common terminal and a second terminal, and an impedance variable circuit. The frequency interval between the Band A and the Band B is smaller than the frequency interval between the Band A and the Band C. In CA of the Band A and the Band B, the filter is connected to the first terminal, the filter is connected to the second terminal, and an impedance of the low pass filter when viewed from the first terminal and an impedance of the high pass filter when viewed from the second terminal have a complex conjugate relationship.