Steep skirt combination microelectromechanical system cavity filter and bulk acoustic wave filter
A combination filter comprises a notch filter formed of acoustic wave resonators and a cavity filter electrically in series with the notch filter to provide for the combination filter to operate at higher powers and frequencies.
1 . A combination filter comprising:
a notch filter formed of acoustic wave resonators and having a non-tunable stopband; and
a cavity filter electrically in series with the notch filter to provide for the combination filter to operate at higher powers and frequencies.
2 . The combination filter of claim 1 wherein the notch filter is formed of bulk acoustic wave resonators.
3 . The combination filter of claim 2 wherein the bulk acoustic wave resonators include piezoelectric films having multiple sub-layers having different crystallographic orientations that provide for the bulk acoustic wave resonators to operate in one of a second overtone mode or a third overtone mode.
4 . The combination filter of claim 3 wherein the bulk acoustic wave resonators include piezoelectric films having two sub-layers having different crystallographic orientations.
5 . The combination filter of claim 3 wherein the bulk acoustic wave resonators include piezoelectric films having four sub-layers, adjacent ones of the four sub-layers having different crystallographic orientations.
6 . The combination filter of claim 3 wherein the bulk acoustic wave resonators include piezoelectric films having multiple sub-layers having different crystallographic orientations that provide for the bulk acoustic wave resonators to operate in the third overtone mode.
7 . The combination filter of claim 1 wherein the notch filter is formed of lamb wave resonators.
8 . The combination filter of claim 7 wherein the cavity filter is a microelectromechanical system cavity filter.
9 . The combination filter of claim 1 wherein an upper end of the non-tunable stopband of the notch filter is aligned with a lower end of a passband of the cavity filter.
10 . The combination filter of claim 1 wherein a lower end of the non-tunable stopband of the notch filter is aligned with an upper end of a passband of the cavity filter.
11 . The combination filter of claim 1 wherein the notch filter is a first notch filter and the combination filter further comprises a second notch filter having a non-tunable stopband in series with the first notch filter and cavity filter.
12 . The combination filter of claim 11 wherein an upper end of the non-tunable stopband of the first notch filter is aligned with a lower end of a passband of the cavity filter and a lower end of the non-tunable stopband of the second notch filter is aligned with an upper end of the passband of the cavity filter.
13 . The combination filter of claim 1 having an operating frequency between about 0.4 and about 7.1 GHz.
14 . The combination filter of claim 1 having an operating frequency between about 24 GHz and about 53 GHz.
15 . The combination filter of claim 1 exhibiting a steeper skirt than the cavity filter alone.
16 . The combination filter of claim 1 exhibiting a greater power handling ability at a given frequency than a ladder filter formed of acoustic wave resonators operating at the given frequency.
17 . A radio frequency front end module including the combination filter of claim 1 .
18 . The radio frequency front end module of claim 17 having an operating frequency within one of the 5G FR1 band or the 5G FR2 band.
19 . An electronic device including the radio frequency front end module of claim 18 .
20 . The combination filter of claim 1 wherein the notch filter includes a lamb wave resonator having a layer of piezoelectric material disposed over a cavity and interdigital transducer electrodes disposed on both upper and lower surfaces of the layer of piezoelectric material.