Multiplexer, high frequency front-end circuit, and communication apparatus
A multiplexer includes a transmission-side filter electrically connected to a common terminal and a transmission input terminal, and a transmission-side filter electrically connected to the common terminal and a transmission input terminal. The transmission-side filter includes a plurality of series arm resonators and a plurality of parallel arm resonators. Capacitance elements are respectively electrically connected in parallel to the series arm resonator and the parallel arm resonator, which are connected most proximately to the common terminal. IDT electrodes of a series arm resonator and a parallel arm resonator connected most proximately to the common terminal do not include a thinning electrode, and others of the series arm resonators and the parallel arm resonators include thinning electrodes.
1. A multiplexer comprising:
a common terminal, a first input-output terminal, and a second input-output terminal;
a first filter electrically connected to the common terminal and the first input-out terminal; and
a second filter having a pass band different from a pass band of the first filter, and electrically connected to the common terminal and the second input-output terminal; wherein
the first filter includes a plurality of series arm resonators provided on a path connecting the common terminal and the first input-output terminal, and a plurality of parallel arm resonators provided between the path and ground;
each of the plurality of series arm resonators and the plurality of parallel arm resonators is an acoustic wave resonator including an interdigital transducer (IDT) electrode provided on a substrate having piezoelectricity;
a capacitance element is electrically connected in parallel to at least one of a first series arm resonator, which is a series arm resonator connected most proximately to the common terminal among the plurality of series arm resonators, and a first parallel arm resonator, which is a parallel arm resonator connected most proximately to the common terminal among the plurality of parallel arm resonators, and the IDT electrode included in the at least one of the first series arm resonator and the first parallel arm resonator does not include a thinning electrode; and
the IDT electrode included in at least one of the series arm resonators excluding the first series arm resonator among the plurality of series arm resonators and the parallel arm resonators excluding the first parallel arm resonator among the plurality of parallel arm resonators, includes a thinning electrode.
2. The multiplexer according to claim 1 , wherein: no capacitance element is connected in parallel to each of the series arm resonators excluding the first series arm resonator among the plurality of series arm resonators, and each of the parallel arm resonators excluding the first parallel arm resonator among the plurality of parallel arm resonators.
3. The multiplexer according to claim 1 , wherein each of the series arm resonators excluding the first series arm resonator among the plurality of series arm resonators and each of the parallel arm resonators excluding the first parallel arm resonator among the plurality of parallel arm resonators, includes a thinning electrode.
4. The multiplexer according to claim 1 , wherein the capacitance element includes a comb-tooth electrode provided on the substrate.
5. The multiplexer according to claim 4 , wherein
the comb-tooth electrode includes a plurality of electrode fingers provided in parallel or substantially in parallel to one another and a pair of busbars that oppose each other across the plurality of electrode fingers; and
the plurality of electrode fingers are provided along a propagation direction of an acoustic wave in the IDT electrode, and are also provided periodically along a direction orthogonal or substantially orthogonal to the propagation direction.
6. The multiplexer according to claim 1 , wherein the substrate includes a piezoelectric film with the IDT electrode provided on one surface of the piezoelectric film, a high acoustic velocity support substrate through which a bulk wave propagates at a higher acoustic velocity than an acoustic velocity of the acoustic wave that propagates through the piezoelectric film, and a low acoustic velocity film which is provided between the high acoustic velocity support substrate and the piezoelectric film, and through which a bulk wave propagates at a lower acoustic velocity than an acoustic velocity of a bulk wave that propagates through the piezoelectric film.
7. The multiplexer according to claim 1 , wherein the multiplexer includes a first duplexer provided with two filters including the first filter, and a second duplexer provided with two filters including the second filter.
8. The multiplexer according to claim 1 , wherein a pass band of the first filter is an uplink frequency band in Band 30 of Long Term Evolution (LTE), and a pass band of the second filter is an uplink frequency band in Band 25 of the LTE.
9. A high frequency front-end circuit comprising:
multiplexer according to claim 1 ; and
an amplifier circuit electrically connected to the multiplexer.
10. A communication apparatus comprising:
an RF signal processing circuit to process a high frequency signal transmitted and received by an antenna element; and
the frequency front-end circuit according to claim 9 to transmit the high frequency signal between the antenna element and the RF signal processing circuit.
11. The communication apparatus according to claim 10 , wherein the first filter and the second filter are each a filter for the high frequency signal.
12. The multiplexer according to claim 1 , wherein
the IDT electrode is defined by a plurality of electrode fingers provided in parallel or substantially in parallel to one another and a pair of busbars that oppose each other across the plurality of electrode fingers; and
the plurality of electrode fingers are provided along a propagation direction of an acoustic wave in the IDT electrode.
13. The multiplexer according to claim 12 , wherein the plurality of electrode fingers and the pair of busbars include a laminated structure including a close contact layer and a main electrode layer.
14. The multiplexer according to claim 6 , wherein the piezoelectric film includes a 50° Y-cut X-propagation LiTaO 3 piezoelectric single crystal or piezoelectric ceramics.
15. The multiplexer according to claim 6 , wherein
the high acoustic velocity support substrate is a silicon substrate; and
low acoustic velocity film includes silicon dioxide.
16. The multiplexer according to claim 1 , wherein the first filter includes a first inductance element electrically connected between a first one of the plurality of parallel arm resonators and ground.
17. The multiplexer according to claim 16 , wherein the first filter further includes a second inductance element electrically connected between a second one of the plurality of parallel arm resonators and ground.
18. The multiplexer according to claim 1 , wherein
the capacitance element is a first capacitance element connected in parallel to the first series arm resonator; and
a second capacitance element is connected in parallel to the first parallel arm resonator.