Filter and Method of Designing an RF Filter

Patent metadata

Field	Value
Publication number	US-2019123717-A1
Application number	US-201816169824-A
Country	US
Kind code	A1
Filing date	Oct 24, 2018
Priority date	Oct 24, 2017
Publication date	Apr 25, 2019
Grant date	—

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, 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.

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

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

4 . The RF filter of claim 1 ,
wherein an acoustically active parallel resonator has a capacitance C active in a shunt path or in the signal path instead of an acoustically inactive capacitor of the capacitance C inactive in the same shunt path or in the signal path, and wherein the capacitance C active of the acoustically active resonator 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 all acoustically inactive resonators comprise a LC resonance circuit.

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 pass band has a center frequency 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 of claim 1 ,
wherein each parallel resonator comprises the electrical connection of the acoustically active resonator and the de-tuning coil, wherein a resonance frequency of the acoustically active resonator is tuned to a frequency higher than a resonance frequency of a resonator of another shunt path, and wherein the de-tuning coil tunes the resonance frequency of the electrical connection of the acoustically active resonator and the de-tuning coil to a frequency lower than the resonance frequency of the acoustically active resonator.

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

12 . A method for forming an RF filter, the method comprising:
providing a first port, a second 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; tuning the electroacoustic resonator to 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 resonance frequency of the electroacoustic resonator.

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

Assignees

• RF360 Europe GmbH

Inventors

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

Classifications

• H03H7/0115

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

• H03H7/1741

  Comprising typical LC combinations, irrespective of presence and location of additional resistors (when resistors are present, also classify in H03H7/06 - H03H7/07) · CPC title

• H03H9/545 Primary

  including active elements · CPC title

• H03H9/542 Primary

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

• H03H9/6483

  Ladder SAW filters · CPC title