High-frequency filter, multiplexer, high-frequency front-end circuit, and communication device
A high-frequency filter coupled between an input-output terminal and another input-output terminal includes series arm resonators, parallel arm resonators, and an inductor defining an LC resonant circuit. Frequencies at a first attenuation pole defined by resonant frequencies or anti-resonant frequencies of the series arm resonators and the parallel arm resonators and a frequency at a second attenuation pole defined by a resonant frequency of the LC resonant circuit are included in one stop band of the high-frequency filter, and the frequencies at the first attenuation pole are located closer than the frequency at the second attenuation pole to a pass band of the high-frequency filter.
1. A high-frequency filter coupled between a first input-output terminal and a second input-output terminal, the high-frequency filter comprising:
at least one elastic wave resonator; and
a first inductor defining a portion of an LC resonant circuit; wherein
a frequency at a first attenuation pole defined by a resonant frequency or an anti-resonant frequency of the at least one elastic wave resonator and a frequency at a second attenuation pole defined by a resonant frequency of the LC resonant circuit are included in one stop band of the high-frequency filter;
the frequency at the first attenuation pole is closer than the frequency at the second attenuation pole to a pass band of the high-frequency filter;
the at least one elastic wave resonator includes a first elastic wave resonator and a second elastic wave resonator;
the high-frequency filter further includes a first capacitor, a second inductor, and a third inductor;
the first inductor, the second inductor, and the second elastic wave resonator are coupled in series on a path connecting the first input-output terminal and the second input-output terminal;
the first capacitor is coupled in parallel to the first inductor;
the first elastic wave resonator is coupled between a ground and a node that is coupled directly to the second inductor on the path;
the third inductor is coupled between a ground and a node that is coupled directly to the second elastic wave resonator on the path;
the first capacitor, together with the first inductor, defines an LC parallel resonant circuit defining the LC resonant circuit;
the second inductor, together with a capacitance component of the first elastic wave resonator, defines a low pass filter; and
the third inductor, together with a capacitance component of the second elastic wave resonator, defines a high pass filter.
2. The high-frequency filter according to claim 1 , wherein the at least one elastic wave resonator is a low pass filter or a high pass filter with a capacitance component.
3. A multiplexer, comprising:
a plurality of filters including at least one high-frequency filter according to claim 1 ; wherein
input terminals or output terminals of the plurality of filters are coupled directly or indirectly to a common terminal.
4. The multiplexer according to claim 3 , wherein the plurality of filters include two filters.
5. The multiplexer according to claim 3 , wherein the plurality of filters include three filters.
6. The multiplexer according to claim 5 , wherein the three filters include:
a filter having a pass band ranging from about 600 MHz to about 960 MHz;
a filter having a pass band ranging from about 1427 MHz to about 2200 MHz; and
a filter having a pass band ranging from about 2300 MHz to about 2690 MHz.
7. The multiplexer according to claim 3 , wherein the plurality of filters include four filters.
8. The multiplexer according to claim 7 , wherein the four filters include:
a filter having a pass band ranging from about 600 MHz to about 960 MHz;
a filter having a pass band ranging from about 1427 MHz to about 2200 MHz;
a filter having a pass band ranging from about 2300 MHz to about 2400 MHz; and
a filter having a pass band ranging from about 2496 MHz to about 2690 MHz.
9. The multiplexer according to claim 3 , wherein the plurality of filters include a low pass filter.
10. The multiplexer according to claim 3 , wherein signals in a plurality of frequency bands corresponding to the respective filters are transmitted and/or received simultaneously.
11. A high-frequency front-end circuit, comprising:
the multiplexer according to claim 3 ; and
a switch coupled directly or indirectly to the multiplexer.
12. A communication device, comprising:
an RF signal processing circuit that processes a high-frequency signal transmitted and/or received via an antenna element; and
the high-frequency front-end circuit according to claim 11 that transmits the high-frequency signal between the antenna element and the RF signal processing circuit.
13. A high-frequency front-end circuit, comprising:
the multiplexer according to claim 3 ; and
an amplification circuit coupled directly or indirectly to the multiplexer.
14. A communication device, comprising:
an RF signal processing circuit that processes a high-frequency signal transmitted and/or received via an antenna element; and
the high-frequency front-end circuit according to claim 13 that transmits the high-frequency signal between the antenna element and the RF signal processing circuit.
15. A high-frequency filter coupled between a first input-output terminal and a second input-output terminal, the high-frequency filter comprising:
at least one elastic wave resonator; and
a first inductor defining a portion of an LC resonant circuit; wherein
a frequency at a first attenuation pole defined by a resonant frequency or an anti-resonant frequency of the at least one elastic wave resonator and a frequency at a second attenuation pole defined by a resonant frequency of the LC resonant circuit are included in one stop band of the high-frequency filter;
the frequency at the first attenuation pole is closer than the frequency at the second attenuation pole to a pass band of the high-frequency filter;
the at least one elastic wave resonator is a first elastic wave resonator;
the high-frequency filter further includes a first capacitor;
the first inductor is provided on a path connecting the first input-output terminal and the second input-output terminal;
the first capacitor is coupled in parallel to the first inductor;
the first elastic wave resonator is coupled between a ground and a node that is coupled directly to the first inductor on the path;
the first capacitor, together with the first inductor, defines an LC parallel resonant circuit defining the LC resonant circuit; and
the first inductor, together with a capacitance component of the first elastic wave resonator, further defines a low pass filter.
16. A multiplexer, comprising:
a plurality of filters including at least one high-frequency filter according to claim 15 ; wherein
input terminals or output terminals of the plurality of filters are coupled directly or indirectly to a common terminal.
17. A high-frequency filter coupled between a first input-output terminal and a second input-output terminal, the high-frequency filter comprising:
at least one elastic wave resonator; and
a first inductor defining a portion of an LC resonant circuit; wherein
a frequency at a first attenuation pole defined by a resonant frequency or an anti-resonant frequency of the at least one elastic wave resonator and a frequency at a second attenuation pole defined by a resonant frequency of the LC resonant circuit are included in one stop band of the high-frequency filter;
the frequency at the first attenuation pole is closer than the frequency at the second attenuation pole to a pass band of the high-frequency filter;
the at least one elastic wave resonator is a second elastic wave resonator;
the high-frequency filter further includes a first capacitor;
the second elastic wave resonator is provided on a path connecting the first input-output terminal and the second input-output terminal;
the first capacitor and the first inductor are coupled in series;
a circuit including the first capacitor and the first inductor coupled in series is coupled between a ground and a node that is coupled directly to the second elastic wave resonator on the path;
the first capacitor, together with the first inductor, defines an LC series resonant circuit defining the LC resonant circuit; and
the first inductor, together with a capacitance component of the second elastic wave resonator, further defines a high pass filter.
18. A multiplexer, comprising:
a plurality of filters including at least one high-frequency filter according to claim 17 ; wherein
input terminals or output terminals of the plurality of filters are coupled directly or indirectly to a common terminal.
19. A high-frequency filter coupled between a first input-output terminal and a second input-output terminal, the high-frequency filter comprising:
at least one elastic wave resonator; and
a first inductor defining a portion of an LC resonant circuit; wherein
a frequency at a first attenuation pole defined by a resonant frequency or an anti-resonant frequency of the at least one elastic wave resonator and a frequency at a second attenuation pole defined by a resonant frequency of the LC resonant circuit are included in one stop band of the high-frequency filter;
the frequency at the first attenuation pole is closer than the frequency at the second attenuation pole to a pass band of the high-frequency filter;
the at least one elastic wave resonator is a second elastic wave resonator;
the high-frequency filter further includes a first capacitor and a third inductor;
the second elastic wave resonator is provided on a path connecting the first input-output terminal and the second input-output terminal;
the first capacitor and the first inductor are coupled in series;
a circuit including the first capacitor and the first inductor coupled in series is coupled between a ground and the path;
the third inductor is coupled between a ground and a node that is coupled directly to the second elastic wave resonator on the path;
the first capacitor, together with the first inductor, defines an LC series resonant circuit defining the LC resonant circuit; and
the third inductor, together with a capacitance component of the second elastic wave resonator, defines a high pass filter.
20. A multiplexer, comprising:
a plurality of filters including at least one high-frequency filter according to claim 19 ; wherein
input terminals or output terminals of the plurality of filters are coupled directly or indirectly to a common terminal.