Multiplexer, high-frequency front end circuit, and communication device
A hybrid multiplexer includes a filter configured to allow a high-frequency signal of an HB to pass therethrough, and a filter configured to allow a high-frequency signal of an MB to pass therethrough, in which the filter includes a matching circuit, a first resonance circuit defined by one of an LPF and an HPF, and a second resonance circuit defined by the other of the LPF and the HPF, the LPF includes an inductor and a parallel arm resonator, the HPF includes a serial arm resonator and an inductor, and a resonant frequency of the parallel arm resonator and an anti-resonant frequency of the serial arm resonator are both located between a frequency at a low-band end of the HB and a frequency at a high-band end of the HB.
1. A multiplexer comprising:
a common terminal;
a first filter connected to the common terminal and configured to allow passing of a first frequency band;
a second filter connected to the common terminal and configured to allow passing of a second frequency band which does not overlap with the first frequency band; wherein
the second filter includes:
a matching circuit connected to the common terminal;
a first resonance circuit cascade connected to the matching circuit and defining one of a low pass filter and a high pass filter; and
a second resonance circuit cascade connected to the first resonance circuit and defining another of the low pass filter and the high pass filter;
the low pass filter includes:
a first inductor provided on a signal path connecting a first terminal and a second terminal of the second filter; and
a first parallel arm resonator that is an acoustic wave resonator connected between a node on the signal path and a ground;
the high pass filter includes:
a first serial arm resonator that is an acoustic wave resonator provided on the signal path; and
a second inductor connected between a node on the signal path and the ground; and
a resonant frequency of the first parallel arm resonator and an anti-resonant frequency of the first serial arm resonator are both located between a frequency at a low-band end of the first frequency band and a frequency at a high-band end of the first frequency band.
2. The multiplexer according to claim 1 , wherein
the frequency at the low-band end of the first frequency band is located at a higher-band side than a frequency at a high-band end of the second frequency band;
the matching circuit is defined by a matching inductor provided in series on the signal path;
the first resonance circuit is the low pass filter; and
the second resonance circuit is the high pass filter.
3. The multiplexer according to claim 2 , wherein
a capacitor connected in parallel to the matching inductor is further included; and
a resonant frequency of a parallel circuit of the matching inductor and the capacitor is located in a frequency band obtained by multiplying the second frequency band by an integer equal to or more than two.
4. The multiplexer according to claim 1 , wherein
the frequency at the high-band end of the first frequency band is located at a lower-band side than a frequency at a low-band end of the second frequency band;
the matching circuit is defined by a matching inductor connected between a node on the signal path and the ground;
the first resonance circuit is the high pass filter; and
the second resonance circuit is the low pass filter.
5. The multiplexer according to claim 1 , wherein
a circuit in which the matching circuit and the first resonance circuit are cascade connected
exhibits low pass characteristics when the frequency at the low-band end of the first frequency band is located at the higher-band side than the frequency at the high-band end of the second frequency band; and
exhibits high pass characteristics when the frequency at the high-band end of the first frequency band is located at the lower-band side than the frequency at the low-band end of the second frequency band.
6. The multiplexer according to claim 1 , wherein the resonant frequency of the first parallel arm resonator is located at a higher-band side than the anti-resonant frequency of the first serial arm resonator.
7. The multiplexer according to claim 1 , wherein
the low pass filter further includes a bridging resonator which is an acoustic wave resonator bridge-connected to the first inductor; and
a sub-anti-resonant frequency which is different from an anti-resonant frequency of the bridging resonator in a circuit in which the first inductor and the bridging resonator are bridge-connected is located between the frequency at the low-band end of the first frequency band and the frequency at the high-band end of the first frequency band.
8. The multiplexer according to claim 7 , wherein the sub-anti-resonant frequency is located between an anti-resonant frequency group of one or more serial arm resonators of the high pass filter and a resonant frequency group of one or more parallel arm resonators of the low pass filter.
9. The multiplexer according to claim 1 , wherein
the low pass filter further includes a second parallel arm resonator which is an acoustic wave resonator connected between a node on the signal path and the ground;
the high pass filter further includes a second serial arm resonator which is an acoustic wave resonator provided on the signal path;
one of the first parallel arm resonator and the second parallel arm resonator is connected to the node on one terminal side of the first inductor and another one of the first parallel arm resonator and the second parallel arm resonator is connected to the node on another terminal side of the first inductor;
a resonant frequency of the second parallel arm resonator is located on a higher-band side than both the anti-resonant frequency of the first serial arm resonator and an anti-resonant frequency of the second serial arm resonator and on a lower-band side than the frequency at the high-band end of the first frequency band;
the first serial arm resonator and the second serial arm resonator are connected to each other with a node, to which the second inductor is connected, on the signal path interposed between the first serial arm resonator and the second serial arm resonator; and
the anti-resonant frequency of the second serial arm resonator is located on a higher-band side than the frequency at the low-band end of the first frequency band and on a lower-band side than both the resonant frequency of the first parallel arm resonator and the resonant frequency of the second parallel arm resonator.
10. The multiplexer according to claim 1 , wherein the resonator of the low pass filter and the resonator of the high pass filter are provided as separate chips.
11. The multiplexer according to claim 1 , further comprising:
a third filter which allows passing of a high-frequency signal of a third frequency band which does not overlap with the first frequency band and the second frequency band.
12. The multiplexer according to claim 1 , further comprising:
a fourth filter which is connected to the common terminal at a closer position to the common terminal than the first filter and the second filter and allows passing of a high-frequency signal of a fourth frequency band which includes the first frequency band and the second frequency band.
13. The multiplexer according to claim 1 , wherein simultaneously passing of a high-frequency signal of one frequency band included in the first frequency band and a high-frequency signal of another frequency band included in the second frequency band are allowed.
14. A high-frequency front end circuit comprising:
the multiplexer according to claim 1 ; and
an amplifier circuit connected to the multiplexer.
15. The high-frequency front end circuit according to claim 14 , wherein
the multiplexer demultiplexes a high-frequency signal input to the common terminal; and
the amplifier circuit is a low noise amplifier configured to amplify the high-frequency signal demultiplexed by the multiplexer.
16. The high-frequency front end circuit according to claim 14 , wherein
the amplifier circuit is a low noise amplifier; and
the multiplexer is a combiner that multiplexes the high-frequency signal amplified by the amplifier circuit and outputs from the common terminal.
17. A high-frequency front end circuit comprising:
the multiplexer according to claim 1 ;
a switch connected to a terminal on an opposite side from the common terminal of the first filter or the second filter; and
a duplexer connected to the first filter or the second filter with the switch interposed between the duplexer and the first filter or the second filter.
18. A communication device comprising:
an RF signal processing circuit configured to process a high-frequency signal; and
the high-frequency front end circuit according to claim 14 configured to transmit the high-frequency signal to be processed by the RF signal processing circuit between an antenna element and the RF signal processing circuit.