Composite filter device, high-frequency front end circuit, and communication apparatus
A composite filter device includes a common terminal disposed on an element substrate including a piezoelectric layer, first and second band pass filters disposed on the element substrate, and connected at one end thereof to the common terminal, a shield electrode interposed between a signal line and the first band pass filter, the signal line being disposed on the element substrate and connecting the common terminal to the first and second band pass filters, and an inductor connected between the shield electrode and a reference potential line.
1. A composite filter device comprising:
an element substrate including a piezoelectric layer;
a common terminal disposed on the element substrate;
a first band pass filter connected at one end thereof to the common terminal, disposed on the element substrate, and including an acoustic wave resonator;
a second band pass filter connected at one end thereof to the common terminal, disposed on the element substrate, and including an acoustic wave resonator;
a signal line disposed on the element substrate and connecting the one end of each of the first and second band pass filters to the common terminal;
a reference potential line disposed on the element substrate and connected to the second band pass filter;
a shield electrode disposed on the element substrate, interposed between the signal line and the first band pass filter, and electrically connected to the reference potential line;
an inductor electrically connected between the shield electrode and the reference potential line; and
the signal line is disposed opposite to the second band pass filter, with the first band pass filter interposed therebetween.
2. The composite filter device according to claim 1 , wherein the first band pass filter includes a plurality of acoustic wave resonators.
3. The composite filter device according to claim 2 , wherein the plurality of acoustic wave resonators include series arm resonators and parallel arm resonators, and the first band pass filter is a ladder filter.
4. The composite filter device according to claim 1 , wherein the shield electrode is belt-shaped and made of a metal film.
5. The composite filter device according to claim 1 , further comprising:
a multilayer substrate; wherein
the element substrate including the first and second band pass filters thereon is mounted on the multilayer substrate.
6. The composite filter device according to claim 5 , wherein the inductor is located in the multilayer substrate.
7. The composite filter device according to claim 1 , wherein the inductor includes a metal film.
8. The composite filter device according to claim 1 , wherein the inductor is a chip inductor.
9. The composite filter device according to claim 6 , further comprising:
a plurality of bumps joining the element substrate to the multilayer substrate; wherein
the shield electrode is connected to at least one of the plurality of bumps that is connected to the inductor in the multilayer substrate.
10. The composite filter device according to claim 1 , wherein the common terminal is an antenna terminal.
11. The composite filter device according to claim 10 , wherein one end of at least one other band pass filter is connected to the common terminal to define a composite filter device for carrier aggregation.
12. The composite filter device according to claim 10 , wherein the first band pass filter and the second band pass filter define and function as a transmit filter and a receive filter, respectively, to define a duplexer.
13. A high-frequency front end circuit comprising:
the composite filter device according to claim 1 ; and
at least one of a switch, a power amplifier, an LNA, a diplexer, a circulator, and an isolator.
14. The high-frequency front end circuit according to claim 13 , wherein the first band pass filter includes a plurality of acoustic wave resonators.
15. The high-frequency front end circuit according to claim 14 , wherein the plurality of acoustic wave resonators include series arm resonators and parallel arm resonators, and the first band pass filter is a ladder filter.
16. The high-frequency front end circuit according to claim 13 , wherein the shield electrode is belt-shaped and made of a metal film.
17. The high-frequency front end circuit according to claim 13 , further comprising:
a multilayer substrate; wherein
the element substrate including the first and second band pass filters thereon is mounted on the multilayer substrate.
18. A communication apparatus comprising:
the high-frequency front end circuit according to claim 13 ; and an RFIC.