Cascaded resonator with different reflector pitch
An acoustic wave device comprises a piezoelectric substrate, interdigital transducer electrodes having an electrode pitch λ 0 , and first and second reflector gratings disposed on opposite respective sides of the interdigital transducer electrodes in a propagation direction of a main acoustic wave through the acoustic wave device, the first reflector grating having a different electrode pitch λ 1 than an electrode pitch λ 2 of the second reflector grating to suppress ripples in a conductance curve of the acoustic wave device.
1. An acoustic wave device comprising:
a piezoelectric substrate;
interdigital transducer electrodes having an electrode pitch λ 0 ; and
first and second reflector gratings disposed on opposite respective sides of the interdigital transducer electrodes in a propagation direction of a main acoustic wave through the acoustic wave device, the first reflector grating having a different electrode pitch λ 1 than an electrode pitch λ 2 of the second reflector grating to suppress ripples in a conductance curve of the acoustic wave device, each of λ 1 and λ 2 being greater than λ 0 by between about 2% and about 5%.
2. The acoustic wave device of claim 1 further comprising:
second interdigital transducer electrodes in series with the interdigital transducer electrodes; and
third and fourth reflector gratings disposed on opposite respective sides of the second interdigital transducer electrodes in the propagation direction, the third reflector grating having a different electrode pitch λ 3 than an electrode pitch λ 4 of the fourth reflector grating.
3. The acoustic wave device of claim 2 wherein λ 1 is equal to one of λ 3 or λ 4 .
4. The acoustic wave device of claim 3 wherein λ 2 is equal to one of λ 3 or λ 4 .
5. The acoustic wave device of claim 2 wherein each of λ 1 , λ 2 , λ 3 , and λ 4 is different.
6. An electronic device including at least two filters coupled to an antenna node, a first of the at least two filters being a ladder filter having a series resonator closest to the antenna node, the series resonator comprising:
a piezoelectric substrate;
interdigital transducer electrodes having an electrode pitch λ 0 ; and
first and second reflector gratings disposed on opposite respective sides of the interdigital transducer electrodes in a propagation direction of a main acoustic wave through the acoustic wave device, the first reflector grating having a different electrode pitch λ 1 than an electrode pitch λ 2 of the second reflector grating to suppress ripples in a conductance curve of the series resonator, each of λ 1 and λ 2 being greater than λ 0 by between about 2% and about 5%.
7. The electronic device of claim 6 further comprising:
second interdigital transducer electrodes in series with the interdigital transducer electrodes; and
third and fourth reflector gratings disposed on opposite respective sides of the second interdigital transducer electrodes in the propagation direction, the third reflector grating having a different electrode pitch λ 3 than an electrode pitch λ 4 of the fourth reflector grating.
8. The electronic device of claim 7 wherein each of λ 1 , λ 2 , λ 3 , and λ 4 is different.
9. The electronic device of claim 7 wherein each of λ 3 , and λ 4 is greater than an electrode pitch of the second interdigital transducer electrodes.
10. The electronic device of claim 7 wherein one of λ 1 or λ 2 is equal to one of λ 3 or λ 4 .
11. An electronic device comprising:
an electronics module including a radio frequency filter, the radio frequency filter including an acoustic wave resonator including a piezoelectric substrate, interdigital transducer electrodes having an electrode pitch λ 0 , and first and second reflector gratings disposed on opposite respective sides of the interdigital transducer electrodes in a propagation direction of a main acoustic wave through the acoustic wave device, the first reflector grating having a different electrode pitch λ 1 than an electrode pitch λ 2 of the second reflector grating to suppress ripples in a conductance curve of the acoustic wave resonator, each of λ 1 and λ 2 being greater than λ 0 by between about 2% and about 5%.
12. The electronic device of claim 11 further comprising:
second interdigital transducer electrodes in series with the interdigital transducer electrodes; and
third and fourth reflector gratings disposed on opposite respective sides of the second interdigital transducer electrodes in the propagation direction, the third reflector grating having a different electrode pitch λ 3 than an electrode pitch λ 4 of the fourth reflector grating.
13. The electronic device of claim 12 wherein each of λ 1 , λ 2 , λ 3 , and λ 4 is different.
14. The electronic device of claim 12 wherein each of λ 3 , and λ 4 is greater than an electrode pitch of the second interdigital transducer electrodes.
15. The electronic device of claim 12 wherein one of λ 1 or λ 2 is equal to one of λ 3 or λ 4 .