Acoustic wave device
An acoustic wave device includes a common terminal, a first terminal, a second terminal, a first filter, a second filter, and an inductor. The first filter has a pass band corresponding to a relatively low frequency range and includes a surface acoustic wave filter using an SH wave. The second filter has a pass band corresponding to a relatively high frequency range. The first filter is between a branch point and the first terminal on a path connecting the common terminal and the first terminal. The second filter is between the branch point and the second terminal on a path connecting the common terminal and the second terminal. The inductor is on a path connecting the branch point and the first filter.
1. An acoustic wave device comprising:
a common terminal;
a first terminal;
a second terminal;
a first filter on a first path connecting the common terminal and the first terminal and having a first pass band;
a second filter on a second path connecting the common terminal and the second terminal and having a second pass band corresponding to a frequency range higher than the first pass band; and
a first phase-shift element; wherein
the first path and the second path share a path from the common terminal to a branch point;
the first filter is a surface acoustic wave filter using an SH wave and is positioned between the branch point and the first terminal;
the second filter is positioned between the branch point and the second terminal;
the first phase-shift element is provided between the branch point and the first filter on the first path; and
in at least a portion of the second pass band, an impedance when a first-terminal side is viewed from between the first phase-shift element and the branch point is located closer to an outermost constant-conductance circle in a Smith chart than an impedance when the first-terminal side is viewed from between the first filter and the first phase-shift element.
2. The acoustic wave device according to claim 1 , wherein a stop band edge on a high-frequency side of the first filter is located between a frequency of a pass band edge on a high-frequency side of the first pass band and a frequency of a pass band edge on a low-frequency side of the second pass band.
3. The acoustic wave device according to claim 1 , wherein the first phase-shift element includes a mount circuit element.
4. The acoustic wave device according to claim 1 , further comprising a second phase-shift element connected between a node on the first path connecting the first filter and the branch point and ground.
5. The acoustic wave device according to claim 4 , wherein the node is on the first path between the first filter and the first phase-shift element.
6. The acoustic wave device according to claim 5 , wherein the second phase-shift element includes a capacitor.
7. The acoustic wave device according to claim 1 , wherein the first phase-shift element includes an inductor.
8. The acoustic wave device according to claim 1 , wherein
the first filter includes:
a high-acoustic-velocity film;
a low-acoustic-velocity film on the high-acoustic-velocity film;
a piezoelectric film on the low-acoustic-velocity film; and
an interdigital-transducer electrode on the piezoelectric film; wherein
an acoustic velocity of a bulk wave that propagates in the high-acoustic-velocity film is higher than an acoustic velocity of an acoustic wave that propagates in the piezoelectric film; and
an acoustic velocity of a bulk wave that propagates in the low-acoustic-velocity film is lower than an acoustic velocity of a bulk wave that propagates in the piezoelectric film.
9. A radio-frequency front-end circuit comprising:
the acoustic wave device according to claim 1 ; and
an amplifier circuit connected to the acoustic wave device.
10. The radio-frequency front-end circuit according to claim 9 , wherein a stop band edge on a high-frequency side of the first filter is located between a frequency of a pass band edge on a high-frequency side of the first pass band and a frequency of a pass band edge on a low-frequency side of the second pass band.
11. The radio-frequency front-end circuit according to claim 9 , wherein the first phase-shift element is defined by a mount circuit element.
12. The radio-frequency front-end circuit according to claim 9 , further comprising a second phase-shift element connected between a node on the first path connecting the first filter and the branch point and ground.
13. The radio-frequency front-end circuit according to claim 12 , wherein the second phase-shift element is a capacitor.
14. The radio-frequency front-end circuit according to claim 12 , wherein the node is on the first path between the first filter and the first phase-shift element.
15. The radio-frequency front-end circuit according to claim 9 , wherein the first phase-shift element is an inductor.
16. The radio-frequency front-end circuit according to claim 9 , wherein
the first filter includes:
a high-acoustic-velocity film;
a low-acoustic-velocity film on the high-acoustic-velocity film;
a piezoelectric film on the low-acoustic-velocity film; and
an interdigital-transducer electrode on the piezoelectric film; wherein
an acoustic velocity of a bulk wave that propagates in the high-acoustic-velocity film is higher than an acoustic velocity of an acoustic wave that propagates in the piezoelectric film; and
an acoustic velocity of a bulk wave that propagates in the low-acoustic-velocity film is lower than an acoustic velocity of a bulk wave that propagates in the piezoelectric film.
17. A communication apparatus comprising:
an RF signal processing circuit that processes a high frequency signal received or to be transmitted by an antenna element; and
the radio-frequency front-end circuit according to claim 9 that communicates the high frequency signal between the antenna element and the RF signal processing circuit.
18. An acoustic wave device comprising:
a common terminal;
a first terminal;
a second terminal;
a first filter on a first path connecting the common terminal and the first terminal and having a first pass band;
a second filter on a second path connecting the common terminal and the second terminal and having a second pass band corresponding to a frequency range higher than the first pass band; and
a first phase-shift element; wherein
the first path and the second path share a path from the common terminal to a branch point;
the first filter is a surface acoustic wave filter using an SH wave and is positioned between the branch point and the first terminal;
the second filter is positioned between the branch point and the second terminal;
the first phase-shift element is provided between the branch point and the first filter on the first path; and
in at least a portion of the second pass band, a constant conductance circle on which an impedance when a first-terminal side is viewed from between the first phase-shift element and the branch point is located is outside a constant conductance circle on which an impedance when the first-terminal side is viewed from between the first filter and the first phase-shift element is located.
19. A radio-frequency front-end circuit comprising:
the acoustic wave device according to claim 18 ; and
an amplifier circuit connected to the acoustic wave device.
20. A communication apparatus comprising:
an RF signal processing circuit that processes a high frequency signal received or to be transmitted by an antenna element; and
the radio-frequency front-end circuit according to claim 19 that communicates the high frequency signal between the antenna element and the RF signal processing circuit.