Dual mode structure (DMS) filter ladder design
Certain aspects of the present disclosure provide a filter. The filter generally includes a series resonator coupled between a first port of the filter and a second port of the filter, and a shunt resonator coupled between a node of the filter and a reference potential node of the filter, the node being coupled between the first port and the second port. The shunt resonator typically includes a first piezoelectric substrate, a first plurality of reflectors disposed above the first piezoelectric substrate, and a first plurality of interdigital transducers (IDTs) disposed above the first piezoelectric substrate and between the first plurality of reflectors, wherein the shunt resonator is configured as a dual mode structure (DMS).
1. A filter comprising:
a series resonator coupled between a first port of the filter and a second port of the filter; and
a shunt resonator coupled between a node of the filter and a reference potential node of the filter, the node being coupled between the first port and the second port, wherein the shunt resonator comprises:
a first piezoelectric substrate;
a first plurality of reflectors disposed above the first piezoelectric substrate; and
a first plurality of interdigital transducers (IDTs) disposed above the first piezoelectric substrate and between the first plurality of reflectors, wherein the shunt resonator is configured as a dual mode structure (DMS).
2. The filter of claim 1 , wherein a frequency response of the shunt resonator is based on a first resonant mode and a second resonant mode of the shunt resonator.
3. The filter of claim 1 , wherein each of the first plurality of IDTs is coupled between the node and the reference potential node.
4. The filter of claim 1 , wherein the series resonator comprises:
a second piezoelectric substrate;
a second plurality of reflectors on the second piezoelectric substrate; and
a second plurality of IDTs on the second piezoelectric substrate, the second plurality of IDTs being disposed between the second plurality of reflectors.
5. The filter of claim 4 , wherein the second piezoelectric substrate is the same as the first piezoelectric substrate.
6. The filter of claim 4 , wherein:
at least one of the second plurality of IDTs is coupled between the first port and the reference potential node; and
at least one other of the second plurality of IDTs is coupled between the reference potential node and the second port.
7. The filter of claim 4 , wherein:
at least two of the second plurality of IDTs is coupled between the first port and the reference potential node; and
another one of the second plurality of IDTs is coupled between the reference potential node and the second port, the other one of the second plurality of IDTs being disposed between the at least two of the second plurality of IDTs.
8. The filter of claim 1 , further comprising an acoustic element coupled between the first port and the second port.
9. The filter of claim 8 , wherein the acoustic element comprises a resonator.
10. The filter of claim 1 , wherein the shunt resonator is configured to set a band-stop frequency range associated with the filter.
11. The filter of claim 1 , wherein the series resonator is configured to set a bandpass frequency range associated with the filter.
12. The filter of claim 1 , wherein the series resonator is configured as a dual mode structure (DMS).
13. The filter of claim 1 , wherein an adjacent pair of IDTs in the first plurality of IDTs of the shunt resonator are electroacoustically coupled.
14. The filter of claim 1 , wherein each of the first plurality of IDTs has a same resonant frequency.
15. The filter of claim 1 , wherein a first IDT of the first plurality of IDTs has a different resonant frequency than a second IDT of the first plurality of IDTs.
16. The filter of claim 1 , further comprising another shunt resonator coupled between another node of the filter and the reference potential node of the filter, the other node being coupled between the first port and the second port, wherein the other shunt resonator comprises:
a second piezoelectric substrate;
a second plurality of reflectors disposed above the second piezoelectric substrate; and
a second plurality of IDTs disposed above the second piezoelectric substrate and between the second plurality of reflectors.
17. The filter of claim 16 , wherein the other shunt resonator is configured as a dual mode structure (DMS).
18. The filter of claim 1 , wherein the first plurality of IDTs comprises at least 3 IDTs.
19. The filter of claim 1 , wherein the first plurality of IDTs comprises at least 5 IDTs.
20. A filter comprising:
a series resonator coupled between a first port of the filter and a second port of the filter; and
a shunt resonator coupled between a node of the filter and a reference potential node of the filter, the node being coupled between the first port and the second port, wherein the shunt resonator is configured as a dual mode structure (DMS).
21. The filter of claim 20 , wherein a frequency response of the shunt resonator is based on a first resonant mode and a second resonant mode of the shunt resonator.
22. The filter of claim 20 , further comprising an acoustic element coupled between the first port and the second port.
23. The filter of claim 22 , wherein the acoustic element comprises a resonator.
24. The filter of claim 20 , wherein the shunt resonator is configured to set a band-stop frequency range associated with the filter.
25. The filter of claim 20 , wherein the series resonator is configured to set a bandpass frequency range associated with the filter.
26. The filter of claim 20 , wherein the series resonator is configured as a dual mode structure (DMS).
27. The filter of claim 20 , further comprising another shunt resonator coupled between another node of the filter and the reference potential node of the filter, the other node being coupled between the first port and the second port.
28. The filter of claim 27 , wherein the other shunt resonator is configured as a dual mode structure (DMS).
29. A method for filtering an input signal, comprising:
receiving the input signal at a first port of a filter; and
generating a filtered version of the input signal at a second port of the filter, the filter comprising:
a series resonator coupled between the first port of the filter and the second port of the filter; and
a shunt resonator coupled between a node of the filter and a reference potential node of the filter, the node being coupled between the first port and the second port, wherein the shunt resonator comprises:
a first piezoelectric substrate;
a first plurality of reflectors disposed above the first piezoelectric substrate; and
a first plurality of interdigital transducers (IDTs) disposed above the first piezoelectric substrate and between the first plurality of reflectors, wherein the shunt resonator is configured as a dual mode structure (DMS).
30. The method of claim 29 , wherein the series resonator is configured as a dual mode structure (DMS).