Techniques are disclosed for increasing capacitance, decreasing losses, and/or improving a quality factor of a SAW filter. The techniques include using a partial-IDT instead of a reflector between two groups of IDTs. The partial-IDT is implemented having a cavity transition on a first end and a reflector transition on a second end. The cavity transition facilitates propagation of main-resonance acoustic waves into, or between elements of, the partial-IDT. The reflector transition facilitates reflection of main-resonance acoustic waves.

A receiving filter includes a reception terminal which outputs reception signals from an antenna terminal, a second DMS filter configured by a longitudinally coupled double-mode type acoustic wave filter which is located in a signal path from the antenna terminal to the reception terminal, a fourth GND terminal given a reference potential, and a fourth GND wiring connected to the fourth GND terminal and to the second DMS filter. A reception terminal conductor configured by the reception terminal and the reception terminal wiring connected to the reception terminal and A fourth GND conductor configured by the fourth GND terminal and the fourth GND wiring are adjacent and are capacity-coupled with respect to each other.

A reception filter includes a parallel arm resonator, a first longitudinally coupled resonance device including first acoustic wave resonators, and a second longitudinally coupled resonance device including second acoustic wave resonators, and cascade-connected to the first longitudinally coupled resonance device. Each of the first and second acoustic wave resonators include one end connected to a ground, the parallel arm resonator and the first and second longitudinally coupled resonance devices are provided on a piezoelectric substrate, and a ground to which the parallel arm resonator is connected, a ground to which at least one of the first acoustic wave resonators is connected, and a ground to which at least one of the second acoustic wave resonators is connected are commonly connected on the piezoelectric substrate.

A radio frequency front-end circuit includes a frequency variable filter connected to a select terminal of a switching circuit, and a filter connected to a select terminal of the switching circuit, the switching circuit including a switch that switches over conduction and non-conduction between a common terminal and the select terminal, the filter including a serial arm resonance circuit connected to the select terminal, a parallel arm resonator, and a frequency varying circuit that is a circuit including a capacitor and a switch connected in parallel to each other, and that is connected in series to the parallel arm resonator, wherein the frequency varying circuit shifts a frequency of the filter depending on conduction and non-conduction of the switch, and an on-resistance of the switch is smaller than an on-resistance of the switch.

Techniques are disclosed for increasing capacitance, decreasing losses, and/or improving a quality factor of a SAW filter. The techniques include using a partial-IDT instead of a reflector between two groups of IDTs. The partial-IDT is implemented having a cavity transition on a first end and a reflector transition on a second end. The cavity transition facilitates propagation of main-resonance acoustic waves into, or between elements of, the partial-IDT. The reflector transition facilitates reflection of main-resonance acoustic waves.

An acoustic wave filter includes: a piezoelectric substrate; a first multimode filter that includes at least three first IDTs located on the piezoelectric substrate, has a first passband, and is connected between an input terminal and an output terminal; and a second multimode filter that includes at least three second IDTs located on the piezoelectric substrate, has a second passband, and is connected in series with the first multimode filter between the input terminal and the output terminal, a part of the second passband overlapping with the first passband, a remaining part of the second passband not overlapping with the first passband.

A longitudinally coupled resonator elastic wave filter is disposed on a piezoelectric substrate. IDT electrodes include first and second busbars. An inorganic insulating layer is provided on at least one side in a direction perpendicular or substantially perpendicular to an elastic wave propagation direction to cover the first or second busbars, and a first wiring line is disposed on the inorganic insulating layer to extend in the elastic wave propagation direction. A second wiring line three-dimensionally crosses the first wiring line with the inorganic insulating layer interposed therebetween. The first wiring line is connected to busbars, which are connected to the same potential, by extending through the inorganic insulating layer.