Bulk acoustic wave resonator filters including rejection-band resonators
A BAW resonator filter can include a BAW resonator pass-band filter ladder, the BAW resonator pass-band filter ladder can be configured to pass frequency components of an input signal in a pass-band of frequencies received at an input node of the BAW resonator pass-band filter ladder to an output node of the BAW resonator pass-band filter ladder. A first rejection-band series resonator can be coupled in series between an input port of the BAW resonator pass-band filter ladder and the input node, the first rejection-band series resonator can have a first anti-resonant frequency peak in a rejection-band of frequencies that is less than the pass-band of frequencies. A second rejection-band series resonator can be coupled in series between an output port of the BAW resonator filter and the output node, the second rejection-band series resonator can have a second anti-resonant frequency peak in the rejection-band of frequencies.
1. A Bulk Acoustic Wave (BAW) resonator filter comprising:
a BAW resonator pass-band filter circuit configured to pass frequency components of an input signal in a pass-band of frequencies received at an input of the BAW resonator pass-band filter circuit to an output of the BAW resonator pass-band filter circuit; and
a first rejection-band shunt resonator coupled in parallel between the input of the BAW resonator pass-band filter circuit and a reference node of the BAW resonator pass-band filter circuit or coupled in parallel between the output the BAW resonator pass-band filter circuit and the reference node, the first rejection-band shunt resonator having a first resonant frequency peak in a rejection-band of frequencies that is greater than the pass-band of frequencies.
2. The BAW resonator filter of claim 1 wherein the BAW resonator pass-band filter circuit comprises a ladder topology, a lattice topology, or a modified lattice topology.
3. The BAW resonator filter of claim 1 wherein the first rejection-band shunt resonator is coupled in parallel across the input of the BAW resonator pass-band filter circuit and the reference node, the BAW resonator filter further comprising:
a second rejection-band shunt resonator coupled in parallel between the output of the BAW resonator filter and the reference node, the second rejection-band shunt resonator having a second resonant frequency peak in the rejection-band of frequencies.
4. The BAW resonator filter of claim 2 wherein the BAW resonator pass-band filter circuit comprises a BAW resonator pass-band filter ladder including:
a plurality of pass-band series resonators coupled in series between the input and the output, the pass-band series resonators having respective resonant frequency peaks in the pass-band of frequencies; and
a plurality of pass-band shunt resonators coupled in parallel with the input and the reference node or in parallel with the output and the reference node of the BAW resonator filter, the pass-band shunt resonators having respective anti-resonant frequency peaks in the pass-band of frequencies.
5. The BAW resonator filter of claim 4 wherein the respective resonant frequency peaks of the pass-band series resonators and the respective anti-resonant frequency peaks of the pass-band shunt resonators are at about a center of the pass-band of frequencies.
6. The BAW resonator filter of claim 5 wherein the respective resonant frequency peaks of the pass-band shunt resonators are at about or less than a lower edge of the pass-band of frequencies and respective anti-resonant frequency peaks of the pass-band series resonators are at about or greater than an upper edge of the pass-band of frequencies.
7. The BAW resonator filter of claim 1 wherein the pass-band of frequencies is about 5.17 GHz to about 5.33 GHz.
8. The BAW resonator filter of claim 7 wherein the rejection-band of frequencies is about 5.49 GHz to about 5.835 GHz.