Filter using transversely-excited film bulk acoustic resonators with inductively coupled sub-resonators

1. A filter comprising:

a first shunt resonator comprising two or more first sub-resonators;

a second shunt resonator comprising two or more second sub-resonators;

at least one series resonator connected to the first and second shunt resonators in a ladder filter circuit; and

a first ground contact pad, wherein:

at least one of the two or more first sub-resonators and at least one, but less than all, of the two or more second sub-resonators are connected to the first ground contact pad.

2. The filter of claim 1 , further comprising:

a second ground contact pad, wherein:

the two or more second sub-resonators not connected to the first ground contact pad are connected to the second ground contact pad.

3. The filter of claim 2 , further comprising:

a third shunt resonator comprising two or more third sub-resonators, wherein;

at least one, but less than all, of the two or more third sub-resonators are connected to the second ground contact pad.

4. The filter of claim 2 , wherein:

the second shunt resonator comprises three second sub-resonators, and

one second sub-resonator of the three second sub-resonators is connected to the first ground contact pad and two other second sub-resonators of the three second sub-resonators are connected to the second ground contact pad.

5. The filter of claim 2 , wherein:

the second shunt resonator comprises four second sub-resonators, and

two second sub-resonators of the fours second sub-resonators are connected to the first ground contact pad and two other second sub-resonators of the fours second sub-resonators are connected to the second ground contact pad.

6. The filter of claim 1 , wherein:

the at least one series resonator is on a first chip,

the first and second shunt resonators and the first ground contact pad are on a second chip.

7. The filter of claim 6 , wherein;

the first chip and the second chip are mounted on a circuit card, and

the first chip, the second chip, and the circuit card collectively form the ladder filter circuit.

8. The filter of claim 1 , wherein:

the first and second shunt resonators and the at least one series resonator are transversely-excited film bulk acoustic resonators (XBARs).

9. A filter comprising:

two or more series resonators connected in series between a first port and a second port;

at least first and second shunt resonators connected to the two or more series resonators in a ladder filter circuit; and

at least a first ground contact pad, wherein:

the first shunt resonator comprises two or more first sub-resonators,

the second shunt resonator comprises two or more second sub-resonators, and

at least one of the two or more first sub-resonators and at least one, but less than all, of the two or more second sub-resonators are connected to the first ground contact pad.

10. The filter of claim 9 , further comprising:

a second ground contact pad, wherein:

the two or more second sub-resonators not connected to the first ground contact pad are connected to the second ground contact pad.

11. The filter of claim 10 , further comprising:

a third shunt resonator comprising two or more third sub-resonators, wherein

at least one, but less than all, of the two or more third sub-resonators are connected to the second ground contact pad.

12. The filter of claim 10 , wherein:

the second shunt resonator comprises three second sub-resonators, and

one second sub-resonator of the three second sub-resonators is connected to the first ground contact pad and two other second sub-resonators of the three second sub-resonators are connected to the second ground contact pad.

13. The filter of claim 10 , wherein:

the second shunt resonator comprises four second sub-resonators, and

two second sub-resonators of the four second sub-resonators are connected to the first ground contact pad and two other second sub-resonators of the four second sub-resonators are connected to the second ground contact pad.

14. The filter of claim 9 , wherein;

the two or more series resonator are on a first chip,

the first and second shunt resonators and the first ground contact pad are on a second chip.

15. The filter of claim 14 , wherein:

the first chip and the second chip are mounted on a circuit card, and

the first chip, the second chip, and the circuit card collectively form the ladder filter circuit.

16. The filter of claim 9 , wherein:

the first and second shunt resonators and the two or more series resonators are transversely-excited film bulk acoustic resonators (XBARs).