Multiplexers are disclosed. A multiplexer can include a first filter and a second filter that are coupled to a common node. The second filter can include a first type of acoustic wave resonators (e.g., bulk acoustic wave resonators) and a series acoustic wave resonator of a second type (e.g., a surface acoustic wave resonator) that is coupled between the acoustic wave resonators of the first type and the common node. The first filter can provide a single-ended radio frequency signal. In certain embodiments, the first filter can be a receive filter and the second filter can be a transmit filter.

A radio frequency module includes a radio frequency filter (10), and the radio frequency filter (10) includes a terminal (11), a terminal (12), an impedance element (Z) disposed in series on a path (13) connecting the terminal (11) and the terminal (12), and a parallel arm resonator (P) connected between a node (N) on the path (13) and a ground. The impedance element (Z) is a capacitor or an inductor, and a wiring length A.sub.1 between the node (N) and the parallel arm resonator (P) is shorter than a wiring length B.sub.1 between the impedance element (Z) and a terminal (terminal (11), for example) out of the terminal (11) and the terminal (12) having a shorter wiring length to the impedance element (Z).

A filter device includes a first substrate, a first input electrode and a first output electrode on the first substrate, a first ground electrode on the first substrate and receiving a ground potential, an electrically open portion in or on the first substrate, a second substrate mounted on the first substrate, a second input electrode on a surface of the second substrate and connected to the first input electrode, a second output electrode on the surface of the second substrate and connected to the first output electrode, a second ground electrode on the surface of the second substrate and connected to the first ground electrode, and at least one first functional electrode on the second substrate and disposed on a first connecting path connecting the second input electrode and the second output electrode. The open portion is connected to the first connecting path.

A multiplexer (100) includes a first filter (FLT1) that passes a signal in a first frequency band, a second filter (FLT2) that passes a signal in a second frequency band lower than the first frequency band, and a third filter (FLT3) that passes a signal in a third frequency band. The third frequency band is a frequency band higher than the first frequency band, or a frequency band lower than the second frequency band. The first filter includes a first inductor (L11) that forms a first attenuation pole on a low-frequency side of the first frequency band. The second filter includes a second inductor (L23) that forms a second attenuation pole on a high-frequency side of the second frequency band. At least a portion of a component constituting the third filter is disposed between the first inductor and the second inductor.

An acoustic wave device includes: a first substrate that has a first surface and a second surface, the second surface being an opposite surface of the first substrate from the first surface; an acoustic wave element that is located on the first surface; a wiring portion that electrically connects the acoustic wave element and a metal portion through a through hole, the metal portion being located on the second surface, the through hole penetrating through the first substrate; and a sealing portion that is located on the first surface so as to surround the acoustic wave element, overlaps with at least a part of the through hole in plan view, and seals the acoustic wave element in an air gap.

A vertically integrated circuit assembly may include a substrate including a plurality of electrical traces, and a first circuit assembly layer disposed on the substrate. In embodiments, the first circuit assembly layer includes a first set of integrated circuit components, and a plurality of electrical interconnects configured to route signals through the first circuit assembly layer. In embodiments, the vertically integrated circuit assembly further includes a second circuit assembly layer coupled to the top surface of the first circuit assembly layer. The second circuit assembly layer may include a second set of integrated circuit components, and a plurality of electrical interconnects configured to route signals through the second circuit assembly layer. In embodiments, an electrical interconnect arrangement on a top surface of the first circuit assembly layer is configured to interface with an electrical interconnect arrangement on the bottom surface of the second circuit assembly layer.

A filter includes first and second signal terminals, a filter circuit connected between the first and second signal terminals, a substrate having first and second surfaces, the first and second signal terminals being located on the first surface, a part of the filter circuit being located at a side of the second surface, a line located closer to the first surface than the filter circuit in the substrate, a first end of the line being connected to one of the first and second signal terminals, and a ground terminal that is located on the first surface and to which a second end of the line is connected, an area of a region where the line overlaps with the ground terminal being greater than an area of a region where the line overlaps with the one of the first and second signal terminals when the substrate is viewed in plan view.

A radio frequency module includes: a module board that includes a first principal surface and a second principal surface on opposite sides of the module board; a power amplifier disposed on the module board; a low noise amplifier disposed on the module board; a transmission filter (a first acoustic wave filter) disposed on one of the first principal surface and the second principal surface; and a reception filter (a second acoustic wave filter) disposed on one of the first principal surface and the second principal surface. An absolute value of a temperature coefficient of frequency (TCF) of the transmission filter is smaller than an absolute value of a TCF of the reception filter, and a distance between the transmission filter and the power amplifier is shorter than a distance between the reception filter and the power amplifier.

A multiplexer includes a first filter that is a ladder elastic wave filter including series-arm resonators and parallel-arm resonators, a second filter connected to the first filter at a common connection point, and a board including an inductor pattern defining an inductor connected in parallel with the series-arm resonator, and a ground pattern provided in the layer in which the inductor pattern is provided, so as to be disposed at a distance from and adjacent to the inductor pattern. A minimum distance between the inductor pattern and the ground pattern is not greater than about 1.55 times a minimum pattern width in the ground pattern.

A radio frequency module includes: a module board including a first principal surface and a second principal surface on opposite sides of the module board; an antenna connection terminal; a diplexer connected to the antenna connection terminal and including at least a first inductor which is a chip inductor; a transmission power amplifier; and a first circuit component disposed on a transmission path connecting the diplexer and the transmission power amplifier. The first inductor is disposed on the first principal surface, and one of the transmission power amplifier and the first circuit component is disposed on the second principal surface.