Multiplexer, radio-frequency front end circuit, and communication device

1. A multiplexer comprising:

a common terminal;

a first band pass filter connected to the common terminal and having a first pass band; and

a second band pass filter connected to the common terminal and having a second pass band located at higher frequencies than the first pass band; wherein

the first band pass filter includes an acoustic wave device that includes a support substrate, a piezoelectric body stacked on the support substrate, and an interdigital transducer (IDT) electrode provided on the piezoelectric body;

the piezoelectric body is made of lithium niobate;

the acoustic wave device utilizes Rayleigh waves; and

an acoustic velocity of a bulk wave propagating in the support substrate is higher than an acoustic velocity of an acoustic wave propagating along the piezoelectric body.

2. The multiplexer according to claim 1 ,

wherein Euler angles (φ, θ, ψ) of the piezoelectric body lie within a range of (0°±5°, θ, 0°±10°), and

the Euler angle θ lies within a range from about 30° to about 38°.

3. The multiplexer according to claim 1 , wherein a film thickness of the piezoelectric body lies within a range from about 0.1λ to about 1.0λ, where λ is a wavelength determined by an electrode finger pitch of the IDT electrode.

4. The multiplexer according to claim 1 , wherein the IDT electrode is made of at least one selected from a group consisting of Pt, Al, Cu, Mo, and Au and alloys containing any of Pt, Al, Cu, Mo, and Au.

5. The multiplexer according to claim 1 , wherein the support substrate is made of aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconia, cordierite, mullite, steatite, forsterite, magnesia, diamond, or a material including any one of aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconia, cordierite, mullite, steatite, forsterite, magnesia, and diamond as a main component.

6. The multiplexer according to claim 1 , wherein a thickness of the IDT electrode is greater than or equal to about 0.02λ, where λ is a wavelength determined by an electrode finger pitch of the IDT electrode.

7. The multiplexer according to claim 6 , wherein the thickness of the IDT electrode is less than or equal to about 0.1λ.

8. The multiplexer according to claim 1 , where the multiplexer is used in carrier aggregation.

9. A radio-frequency front end circuit comprising:

the multiplexer according to claim 1 ; and

a power amplifier.

10. A communication device comprising:

the radio-frequency front end circuit according to claim 9 ; and

an RF signal processing circuit.

11. A multiplexer comprising:

a common terminal;

a first band pass filter connected to the common terminal and having a first pass band; and

a second band pass filter connected to the common terminal and having a second pass band located at higher frequencies than the first pass band; wherein

the first band pass filter includes an acoustic wave device that includes a support substrate, a piezoelectric body stacked on the support substrate, an interdigital transducer (IDT) electrode provided on the piezoelectric body, and a low-acoustic-velocity material layer provided between the support substrate and the piezoelectric body;

the piezoelectric body is made of lithium niobate;

the acoustic wave device utilizes Rayleigh waves; and

the low-acoustic-velocity material layer is made of a low-acoustic-velocity material in which an acoustic velocity of a bulk wave propagating therein is lower than an acoustic velocity of an acoustic wave propagating along the piezoelectric body.

12. The multiplexer according to claim 11 , further comprising:

a high-acoustic-velocity material layer provided between the support substrate and the low-acoustic-velocity material and in which an acoustic velocity of a bulk wave propagating therein is higher than an acoustic velocity of an acoustic wave propagating along the piezoelectric body.

13. The multiplexer according to claim 11 ,

wherein Euler angles (φ, θ, ψ) of the piezoelectric body lie within a range of (0°±5°, θ, 0°±10°), and

the Euler angle θ lies within a range from about 30° to about 38°.

14. The multiplexer according to claim 11 , wherein a film thickness of the piezoelectric body lies within a range from about 0.1λ to about 1.0λ, where λ is a wavelength determined by an electrode finger pitch of the IDT electrode.

15. The multiplexer according to claim 11 , wherein the IDT electrode is made of at least one selected from a group consisting of Pt, Al, Cu, Mo, and Au and alloys containing any of Pt, Al, Cu, Mo, and Au.

16. The multiplexer according to claim 11 , wherein the support substrate is made of aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconia, cordierite, mullite, steatite, forsterite, magnesia, diamond, or a material including any one of aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconia, cordierite, mullite, steatite, forsterite, magnesia, and diamond as a main component.

17. The multiplexer according to claim 11 , wherein a thickness of the IDT electrode is greater than or equal to about 0.02λ, where λ is a wavelength determined by an electrode finger pitch of the IDT electrode.

18. The multiplexer according to claim 17 , wherein the thickness of the IDT electrode is less than or equal to about 0.1λ.

19. The multiplexer according to claim 11 , where the multiplexer is used in carrier aggregation.

20. A radio-frequency front end circuit comprising:

the multiplexer according to claim 11 ; and

a power amplifier.

21. A communication device comprising:

the radio-frequency front end circuit according to claim 20 ; and

an RF signal processing circuit.