Bulk acoustic wave filter for second harmonic residue reduction
View Patent ↗Aspects of this disclosure relate to acoustic wave filters with second harmonic emission suppression. In an embodiment, an acoustic wave filter includes a first bulk acoustic wave resonator, a second bulk acoustic wave resonator in anti-parallel with the first bulk acoustic wave resonator, and a passive impedance element in series with the first bulk acoustic wave resonator. The passive impedance element can reduce an imbalance in resonant frequency between the first and second bulk acoustic wave resonators. Other embodiments of acoustic wave filters with second harmonic emission suppression are disclosed. Related multiplexers, radio frequency modules, wireless communication devices, and methods are disclosed.
1 . An acoustic wave filter with second harmonic emission suppression, the acoustic wave filter comprising:
a first bulk acoustic wave resonator;
a second bulk acoustic wave resonator in anti-parallel with the first bulk acoustic wave resonator; and
a passive impedance element in series with the first bulk acoustic wave resonator and in parallel with the second bulk acoustic wave resonator, the passive impedance element being an inductor, the passive impedance element configured to cause to an imbalance in resonant frequency between the first and second bulk acoustic wave resonators to be reduced, and the acoustic wave filter configured to filter a radio frequency signal.
2 . The acoustic wave filter of claim 1 wherein the first and second bulk acoustic wave resonators are series resonators.
3 . The acoustic wave filter of claim 2 wherein the first and second bulk acoustic wave resonators are included in a first series stage of the acoustic wave filter from an antenna node of the acoustic wave filter.
4 . The acoustic wave filter of claim 2 wherein the acoustic wave filter is a transmit filter.
5 . The acoustic wave filter of claim 1 wherein the first and second bulk acoustic wave resonators are shunt resonators.
6 . The acoustic wave filter of claim 5 wherein the acoustic wave filter is a receive filter.
7 . The acoustic wave filter of claim 1 further comprising a plurality of additional bulk acoustic wave resonators.
8 . A method of radio frequency signal processing with second harmonic emission suppression, the method comprising:
amplifying a radio frequency signal; and
filtering the radio frequency signal with the acoustic wave filter of claim 1 .
9 . An acoustic wave filter with second harmonic emission suppression, the acoustic wave filter comprising:
a first bulk acoustic wave resonator;
a second bulk acoustic wave resonator in anti-parallel with the first bulk acoustic wave resonator, the first and second bulk acoustic wave resonators are shunt resonators; and
a passive impedance element in series with the first bulk acoustic wave resonator, the passive impedance element configured to cause to an imbalance in resonant frequency between the first and second bulk acoustic wave resonators to be reduced, the acoustic wave filter is configured to filter a radio frequency signal, the acoustic wave filter is included in a multiplexer, and the first and second bulk acoustic wave resonators are included in a first shunt stage of the acoustic wave filter from a common node of the multiplexer.
10 . The acoustic wave filter of claim 9 wherein the passive impedance element is a capacitor.
11 . The acoustic wave filter of claim 9 wherein the passive impedance element is an inductor.
12 . The acoustic wave filter of claim 9 wherein the acoustic wave filter is a receive filter.
13 . A multiplexer with second harmonic emission suppression, the multiplexer comprising:
a first acoustic wave filter including a first bulk acoustic wave resonator, a second bulk acoustic wave resonator in anti-parallel with the first bulk acoustic wave resonator, and a passive impedance element in series with the first bulk acoustic wave resonator and in parallel with the second bulk acoustic wave resonator, the passive impedance element being an inductor, the passive impedance element configured to cause to an imbalance in resonant frequency between the first and second bulk acoustic wave resonators to be reduced; and
a second acoustic wave filter coupled to the first acoustic wave filter at a common node.
14 . The multiplexer of claim 13 wherein the first acoustic wave filter further includes a plurality of additional bulk acoustic wave resonators.
15 . The multiplexer of claim 13 wherein the first and second bulk acoustic wave resonators are series resonators.
16 . The multiplexer of claim 15 wherein the first acoustic wave filter is a transmit filter.
17 . The multiplexer of claim 15 wherein the first and second bulk acoustic wave resonators are included in a first series stage of the first acoustic wave filter from the common node.
18 . The multiplexer of claim 13 wherein the first and second bulk acoustic wave resonators are shunt resonators.
19 . The multiplexer of claim 18 wherein the first acoustic wave filter is a receive filter, and the second acoustic wave filter is a transmit filter.
20 . The multiplexer of claim 18 wherein the first and second bulk acoustic wave resonators are in a first shunt stage of the first acoustic wave filter from the common node.