Multiplexer with filter including different types of acoustic wave resonators
Aspects of this disclosure relate to multiplexers with acoustic wave resonators. The multiplexer includes a first filter and a second filter. The first filter includes a plurality of bulk acoustic wave resonators and a shunt surface acoustic wave resonator. The shunt acoustic wave resonator can have a resonant frequency in a passband of the second filter. The passband of the second filter is below a passband of the first filter. In certain applications, the first filter is a receive filter and the second filter is a transmit filter.
1. A multiplexer with acoustic wave resonators, the multiplexer comprising:
a first filter configured to filter a radio frequency signal, the first filter having a first passband, and the first filter including a plurality of bulk acoustic wave resonators and a shunt surface acoustic wave resonator; and
a second filter coupled to the first filter at a common node, the second filter having a second passband that is below the first passband, and the shunt surface acoustic wave resonator having a resonant frequency that is in the second passband.
2. The multiplexer of claim 1 wherein the first filter is a receive filter.
3. The multiplexer of claim 2 wherein the second filter is a transmit filter.
4. The multiplexer of claim 1 wherein the shunt surface acoustic wave resonator is configured to cause second harmonic distortion at the common node to be reduced.
5. The multiplexer of claim 1 wherein the shunt surface acoustic wave resonator is an only surface acoustic wave resonator of the first filter.
6. The multiplexer of claim 1 wherein the shunt surface acoustic wave resonator is a first shunt acoustic wave resonator of the first filter from the common node.
7. The multiplexer of claim 1 wherein the shunt surface acoustic wave resonator and the plurality of bulk acoustic wave resonators are all acoustic wave resonators of the first filter.
8. The multiplexer of claim 1 wherein the shunt surface acoustic wave resonator is a temperature compensated surface acoustic wave resonator.
9. The multiplexer of claim 1 wherein the shunt surface acoustic wave resonator is a multilayer piezoelectric substrate surface acoustic wave resonator.
10. The multiplexer of claim 1 wherein the second filter includes a second plurality of bulk acoustic wave resonators.
11. The multiplexer of claim 1 wherein the first filter includes a series surface acoustic wave resonator and all of the plurality of bulk acoustic wave resonators are coupled to the common node by way of the series surface acoustic wave resonator.
12. The multiplexer of claim 11 wherein the second filter includes a second plurality of bulk acoustic wave resonators, the second plurality of bulk acoustic wave resonators including shunt bulk acoustic wave resonators and series bulk acoustic wave resonators.
13. The multiplexer of claim 1 further comprising a third filter coupled to the common node.
14. The multiplexer of claim 1 wherein the second passband is associated with a fifth generation New Radio band.
15. A multiplexer including acoustic wave filters, the multiplexer comprising:
a transmit filter including a plurality of acoustic wave resonators, the transmit filter configured to filter a radio frequency signal, and the transmit filter having a transmit passband; and
a receive filter coupled to the transmit filter at a common node, the receive filter including a plurality of bulk acoustic wave resonators and a shunt surface acoustic wave resonator, the shunt surface acoustic wave resonator having a resonant frequency in the transmit passband.
16. The multiplexer of claim 15 wherein the plurality of acoustic wave resonators include bulk acoustic wave resonators, and the shunt surface acoustic wave resonator is a first shunt acoustic wave resonator of the receive filter from the common node.
17. A multiplexer including acoustic wave filters, the multiplexer comprising:
a first acoustic wave filter coupled to a common node, the first acoustic wave filter configured to filter a radio frequency signal, and the first acoustic wave filter having a passband;
a second acoustic wave filter coupled to the common node; and
a third acoustic wave filter coupled to the common node, the third acoustic wave filter including a plurality of bulk acoustic wave resonators and a shunt surface acoustic wave resonator, the shunt surface acoustic wave resonator having a resonant frequency in the passband.
18. The multiplexer of claim 17 wherein the third acoustic wave filter is a receive filter, and the first acoustic wave filter is a transmit filter.
19. The multiplexer of claim 17 wherein the shunt surface acoustic wave resonator is a first shunt acoustic wave resonator of the third acoustic wave filter from the common node.
20. The multiplexer of claim 17 wherein the shunt surface acoustic wave resonator and the plurality of bulk acoustic wave resonators are all acoustic wave resonators of the third acoustic wave filter.