A duplexer is provided with high isolation and high steepness on low-frequency side of a receiving band, including an antenna terminal, a transmitting terminal and a receiving terminal arranged on a piezoelectric substrate, where a transmitting filter is connected between the antenna terminal and the transmitting terminal; a receiving filter, with a series arm and multiple parallel arms connected to the series arm, is connected between the antenna terminal and the receiving terminal; the series arm is provided with a DMS filter and multiple series arm resonators; each parallel arm is provided with a parallel arm resonator; and the DMS filter is in common ground connection with all the parallel arm resonators of the receiving filter. The duplexer can better improve the passband isolation and increase the steepness on the low-frequency side of the high passband without additional components and structural complexity, thereby improving performance and providing high practicability.

A filter device includes a filter circuit that is connected to terminals, is defined by a first acoustic wave resonator that has a first frequency band as a pass band, and an additional circuit that is connected in parallel to at least one first acoustic wave resonator between the terminal and the terminal. The additional circuit is defined by a second acoustic wave resonator in which an electromechanical coupling coefficient of the additional circuit is different from an electromechanical coupling coefficient of the filter circuit.

An improved DMS filter with electrode structures between a first port and a second port is provided. Wiring junctions are realized in multilayer crossing with dielectric material in between. There are insulating patches (L2) between crossing conductor layers (L1,L3). Signal wirings may be realized with multiple conductor layers (L1, L3) to reduce wiring resistance and the upper conductor layer (L3) of the signal wiring may partly overlap the insulating patches (L2). The insulating patches (L2) may extend over the acoustic path to achieve temperature compensation.

A radio frequency (RF) filter having a first passband and including a first circuit connected to a first node and a second node disposed on a path that connects a first terminal and a second terminal, and a second circuit connected to the first node and the second node. The first circuit includes a first filter having a second passband that includes a portion of a frequency range of the first passband and a bandwidth narrower than a bandwidth of the first passband. The second circuit includes a second filter having a third passband that includes a portion of a frequency range of the first passband and has a bandwidth narrower than the bandwidth of the first passband. The RF filter also includes a first phase shifter connected to a first terminal of the second filter; and a second phase shifter connected to a second terminal of the second filter.

A multiplexer includes a transmit filter circuit, a receive filter circuit, and an additional circuit connected in parallel with a portion of the transmit filter circuit. The transmit filter circuit includes series resonators on a signal path connecting a common terminal and a first terminal, and parallel resonators on the signal path between a node and ground. The series resonator closest to the first terminal includes split resonators. The additional circuit includes a capacitor and a resonator group. The resonator group includes IDT electrodes side by side in the direction of acoustic wave propagation. A first end of the resonator group is connected to the common terminal with the capacitor interposed therebetween. A second end of the resonator group is connected to the signal path between two of the split resonators such that no capacitor is interposed between the second end and the signal path.

An elastic wave device includes a substrate, a multilayer film located on the substrate, an LT layer located on the multilayer film and made of a single crystal of LiTaO.sub.3, and an IDT electrode located on the LT layer. The LT layer has a thickness of 0.3λ or less, where λ is twice a pitch of electrode fingers of the IDT electrode. The LT layer has Euler angles of (0°±10°, −25° or more and 15° or less, 0° or more and 360° or less).

A surface acoustic wave resonator comprises at least one set of interdigital transducer (IDT) electrodes disposed on an upper surface of a piezoelectric substrate between first and second reflector gratings, a layer of silicon nitride disposed over the at least one set of IDT electrodes and the first and second reflector gratings, and a continuous trench formed in the layer of silicon nitride over portions of bus bar electrodes and tips of electrode fingers of the at least one set of IDT electrodes and over portions of bus bar electrodes and electrode fingers of the first and second reflector gratings to reduce acoustic leakage at electrode fingers of the first and second reflector gratings proximate the at least one set of IDT electrodes.

An electronic device comprises a first surface acoustic wave (SAW) resonator and a second SAW resonator, each including interleaved interdigital transducer (IDT) electrodes, the first and second SAW resonators being formed on a same piezoelectric substrate, the first SAW resonator having IDT electrodes with a different finger pitch than the IDT electrodes of the second SAW resonator; a dielectric material layer disposed on the IDT electrodes of the first and second SAW resonators; and a high velocity layer disposed within the dielectric material layer disposed on the IDT electrodes of the first SAW resonator, the second SAW resonator lacking a high velocity layer disposed within the dielectric material layer disposed on the IDT electrodes.

The present disclosure relates to a ladder-type surface acoustic wave (SAW) device, which includes a piezoelectric layer, two reflective structures, at least one series interdigital transducer (IDT) coupled between a first signal point and a second signal point, and at least one shunt IDT. The at least one shunt IDT is coupled at least between the first signal point and ground, or between the second signal point and ground. Herein, the two reflective structures, the at least one series IDT, and the at least one shunt IDT reside over the piezoelectric layer. The at least one series IDT and the at least one shunt IDT are arranged between the two reflective structures.

A composite filter device includes an antenna common terminal, a first band pass filter having a first pass band, and a second band pass filter having a second pass band located at higher frequencies than the first pass band. The first band pass filter includes an elastic wave resonator. The elastic wave resonator includes a LiNbO.sub.3 substrate, an IDT electrode on the LiNbO.sub.3 substrate, and a dielectric film that covers the IDT electrode and includes a silicon oxide as a main component. When f1′ is the frequency of a Sezawa wave of the first band pass filter and f2 is the center frequency of the second pass band, f1′ is located at a different position from f2.