Filter and method of designing an RF filter

Patent metadata

Field	Value
Publication number	US-10840885-B2
Application number	US-201816169824-A
Country	US
Kind code	B2
Filing date	Oct 24, 2018
Priority date	Oct 24, 2017
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

A filter and a method for forming a filter are disclosed. In an embodiment a filter includes a first port, a second port and a signal path between the first port and the second port. The filter further includes a plurality of series resonators electrically connected in series in the signal path, a plurality of shunt paths, each electrically connecting the signal path to ground and one parallel resonator electrically connected in each shunt path, wherein at least one series resonator is an electroacoustic resonator, and wherein at least one parallel resonator comprises one acoustically inactive capacitor or an electrical connection of an acoustically active resonator and a de-tuning coil.

First claim

What is claimed is:

1. An RF filter comprising:
a first port;
a second port;
a signal path between the first port and the second port;
a plurality of series resonators electrically connected in series in the signal path;
a plurality of shunt paths, wherein each shunt path electrically connects the signal path to ground; and
a respective parallel resonator electrically connected in each shunt path of the plurality of shunt paths,
wherein at least one series resonator of the plurality of series resonators is an electroacoustic resonator, and
wherein the parallel resonator in at least one shunt path of the plurality of shunt paths comprises an electrical connection of an acoustically active resonator and a de-tuning coil, the acoustically active resonator having a higher resonance frequency than another parallel resonator in another shunt path of the plurality of shunt paths, wherein the de-tuning coil has an inductance value that tunes a resonance frequency of the parallel resonator in the at least one shunt path to be lower than the higher resonance frequency of the acoustically active resonator.

2. The RF filter of claim 1 , wherein the acoustically active resonator and the de-tuning coil are electrically connected in series.

3. The RF filter of claim 1 , wherein all series resonators of the plurality of series resonators are electroacoustic resonators.

4. The RF filter of claim 1 ,
wherein at least one of either the plurality of series resonators or respective parallel resonator in each of the plurality of shunt paths is acoustically active, has a capacitance C active , and is a replacement of an acoustically inactive capacitor of the capacitance C inactive , and
wherein the capacitance C active is between 0.5 C inactive and 2.0 C inactive .

5. The RF filter of claim 1 , wherein each electroacoustic resonator is a BAW resonator or a SAW resonator.

6. The RF filter of claim 1 , wherein the at least one shunt path is a first shunt path, wherein the RF filter further comprises an LC resonance circuit that forms at least one of: the parallel resonator in a second shunt path of the plurality of shunt paths; or at least one series resonator of the plurality of series resonators.

7. The RF filter of claim 1 , wherein the RF filter provides a first pass band.

8. The RF filter of claim 7 , wherein the first pass band has a center frequency that is greater than or equal to 3 GHz.

9. The RF filter of claim 7 , wherein the RF filter provides a second pass band with a center frequency ≥3 GHz.

10. The RF filter claim 1 , wherein bulk waves increase an insertion loss in a frequency range outside a pass band.

11. A method for forming an RF filter, the method comprising:
providing a first port, a second port, and a signal path between the first port and the second port;
providing a shunt path electrically connecting the signal path to ground;
electrically connecting a parallel electroacoustic resonator and a de-tuning coil in the shunt path;
forming the parallel electroacoustic resonator to have a higher resonance frequency; and
tuning a resonance frequency of the electrical connection of the parallel electroacoustic resonator and the de-tuning coil to a frequency lower than the higher resonance frequency of the parallel electroacoustic resonator.

12. The method of claim 11 , wherein bulk waves of the parallel electroacoustic resonator are used to increase out-of-band suppression of the RF filter.

13. An RF filter comprising:
a first port;
a second port;
a signal path between the first port and the second port;
a plurality of series resonators electrically connected in series in the signal path;
a plurality of shunt paths, wherein each of the plurality of shunt paths electrically connects the signal path to ground; and
a respective parallel resonator electrically connected in each shunt path of the plurality of shunt paths,
wherein at least one series resonator of the plurality of series resonators is an electroacoustic resonator, and
wherein the parallel resonator in at least one shunt path of the plurality of shunt paths comprises one acoustically inactive capacitor or an electrical connection of an acoustically active resonator and a de-tuning coil, wherein bulk waves of the acoustically active resonator increase an insertion loss in a frequency range outside a pass band of the RF filter.

14. The RF filter of claim 13 , the acoustically active resonator having a higher resonance frequency than another parallel resonator in another shunt path of the plurality of shunt paths, wherein the de-tuning coil has an inductance value that tunes a resonance frequency of the parallel resonator in the at least one shunt path lower than the higher resonance frequency of the acoustically active resonator.

15. An RF filter comprising:
a first port;
a second port;
a signal path between the first port and the second port;
a plurality of series resonators electrically connected in series in the signal path;
a plurality of shunt paths, wherein each shunt path electrically connects the signal path to ground; and
a respective parallel resonator electrically connected in each shunt path of the plurality of shunt paths,
wherein at least one series resonator of the plurality of series resonators is an electroacoustic resonator, and
wherein the parallel resonator in at least one shunt path of the plurality of shunt paths comprises an electrical connection of an acoustically active resonator and a de-tuning coil, the acoustically active resonator having a higher resonance frequency that is outside a pass band of the RF filter, wherein the de-tuning coil has an inductance value that tunes a resonance frequency of the parallel resonator in the at least one shunt path to be lower than the higher resonance frequency of the acoustically active resonator.

16. The RF filter claim 15 , wherein bulk waves of the acoustically active resonator increase suppression in a frequency range outside the pass band.

Assignees

• RF360 Europe GmbH
• Qualcomm Inc

Inventors

• Gavryliuk Oleksandr
• Shevelov Mykola
• Komakha Petro
• Sevskiy Georgiy
• Chernyakov Alexander
• Wong Wai San

Classifications

• H03H9/542 Primary

  including passive elements (H03H9/545 takes precedence) · CPC title

• H03H9/6483

  Ladder SAW filters · CPC title

• H03H9/6489

  Compensation of undesirable effects · CPC title

• H03H9/605

  consisting of a ladder configuration · CPC title

• H03H7/0115

  comprising only inductors and capacitors (H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence) · CPC title