An elastic wave apparatus includes a multilayer substrate, first through fourth band pass filters, an antenna terminal, and first and second inductors. The multilayer substrate includes first through sixth wiring layers. The first through fourth band pass filters are disposed on the multilayer substrate and are connected to a common node. The antenna terminal is connected to an antenna and also to the common node. The first inductor is connected to the antenna terminal. The second inductor is connected between the first band pass filter and the common node. The first inductor is disposed on the fourth and fifth wiring layers. The second inductor is disposed on the second and third wiring layers which are different from the fourth and fifth wiring layers. The first and second inductors overlap each other at least partially as viewed from above.

A filter includes a resonant circuit defining at least a portion of a signal path connected between a first terminal and a second terminal, an elastic wave resonator including one end that is grounded, a first inductor including one end connected to one end of the resonant circuit and another end connected to another end of the elastic wave resonator, and a second inductor including one end connected to another end of the resonant circuit and another end connected to the other end of the elastic wave resonator. The resonant circuit is an LC series resonant circuit in which a third inductor and first and second capacitors are connected in series with each other.

A multiplexer includes a switch that individually connects or disconnects between a common terminal and first, second, third, and fourth selection terminals, first and second matching circuits, and first, second, and third filters having different pass bands. The first selection terminal is connected to one end of the first matching circuit, the second selection terminal is connected to one end of the second matching circuit, the other end of the first matching circuit and the other end of the second matching circuit are connected to each other and to one end of the first filter, the third selection terminal is connected to one end of the second filter, and the fourth selection terminal is connected to one end of the third filter.

A multiplexer includes a common terminal, a first reception output terminal, a second reception output terminal, a first filter that is connected between the common terminal and the first reception output terminal, a second filter that is connected between the common terminal and the second reception output terminal and that has a passband different from that of the first filter, and an impedance matching circuit that is disposed between the common terminal and the second filter. The impedance matching circuit includes a serial arm resonator disposed in series on a path connecting the common terminal to the second filter.

An apparatus includes an RF apparatus, and a multi-band matching balun coupled to the RF apparatus. The multi-band matching balun includes at least one three-element frequency-dependent resonator (TEFDR) and at most three reactive elements.

A surface acoustic wave device includes: a substrate; an electrode disposed on the substrate in a first direction; a dummy bar disposed to be spaced apart from the electrode by a predetermined distance in the first direction; and an additional film formed on the dummy bar, wherein the electrode and the dummy bar are disposed in plurality in parallel in a second direction perpendicular to the first direction, and the dummy bars are alternately disposed on a left side or a right side of the electrode to be spaced apart from the electrode by the predetermined distance, and the additional film is formed on the predetermined distance between the electrode and the dummy bar and on the plurality of dummy bars.

A duplexer includes first and second filter circuits and first and second wirings. The first filter circuit allows a signal of a first frequency band to pass therethrough between a first terminal and a common terminal and includes a first resonator which is connected at one end to a line disposed between the first terminal and the common terminal to branch off from the line. The second filter circuit allows a signal of a second frequency band, which is different from the first frequency band, to pass therethrough between a second terminal and the common terminal. The first wiring is connected at one end to the common terminal and is opened at the other end. The second wiring is connected at one end to the other end of the first resonator and is grounded at the other end. The first wiring is electromagnetically coupled with second wiring.

A self-tuning impedance-matching microelectromechanical (MEMS) circuit, methods for making and using the same, and circuits including the same are disclosed. The MEMS circuit includes a tunable reactance element connected to a first mechanical spring, a separate tunable or fixed reactance element, and an AC signal source configured to provide an AC signal to the tunable reactance element(s). The reactance elements comprise a capacitor and an inductor. The AC signal source creates an electromagnetically energy favorable state for the tunable reactance element(s) at resonance with the AC signal. The method of making generally includes forming a first MEMS structure and a second mechanical or MEMS structure in/on a mechanical layer above an insulating substrate, and coating the first and second structures with a conductor to form a first tunable reactance element and a second tunable or fixed reactance element, as in the MEMS circuit.

An electronics package includes a semiconductor substrate having one or more passive devices formed thereon and a cavity defined in a first surface thereof. A piezoelectric substrate is bonded to the semiconductor substrate and has a radio frequency (RF) filter formed thereon. The RF filter is disposed within the cavity defined in the semiconductor substrate.

The specification relates to an RF filter in which characteristic filter variables have a decreased dependency on tuning. A filter in this case comprises series-interconnected basic elements that each have an electroacoustic resonator and impedance converters interconnected in series between the basic elements.