Bandpass filter with improved upper band edge sharpness

Patent metadata

Field	Value
Publication number	US-12206389-B2
Application number	US-202217697827-A
Country	US
Kind code	B2
Filing date	Mar 17, 2022
Priority date	Nov 30, 2018
Publication date	Jan 21, 2025
Grant date	Jan 21, 2025

Abstract

Bandpass filters are disclosed. A bandpass filter includes a plurality of series resonators and a plurality of shunt resonators. The series resonators are connected in series between a first port and a second port. The plurality of series resonators includes a first series resonator and a second series resonator connected at a node. The plurality of shunt resonators includes a first shunt resonator coupled between the node and a ground. A capacitor bridges the first and second series resonators.

First claim

It is claimed:

1. A bandpass filter comprising:
a plurality of series resonators connected in series between a first port and a second port, the plurality of series resonators including a first series resonator and a second series resonator connected at a node;
a plurality of shunt resonators including a first shunt resonator coupled between the node and a ground;
a first capacitor bridging the first and second series resonators; and
a second capacitor connected in series with the first shunt resonator between the node and the ground, wherein a series combination of the first shunt resonator and the second capacitor has a resonance frequency greater than an upper limit of a passband of the passband filter.

2. The bandpass filter of claim 1 , wherein the first and second series resonators are electrically identical.

3. The bandpass filter of claim 1 , wherein a resonance frequency of the first shunt resonator is greater than a resonance frequency of the first and second series resonators.

4. The bandpass filter of claim 3 , wherein the resonance frequency of the first shunt resonator is proximate to the upper limit of the passband.

5. The bandpass filter of claim 1 , wherein
the plurality of series resonators includes at least a third series resonator, and
the plurality of shunt resonators includes at least three shunt resonators.

6. A bandpass filter comprising:
a plurality of series resonators connected in series between a first port and a second port, the plurality of series resonators including a first series resonator and a second series resonator connected at a node;
a first capacitor bridging the first and second series resonators; and
a series combination of a first shunt resonator and second capacitor coupled between the node and a ground, wherein
the series combination of the first shunt resonator and the second capacitor has a resonance frequency greater than an upper limit of a passband of the bandpass filter.

7. The bandpass filter of claim 6 , wherein the plurality of series resonators includes at least a third series resonator.

8. The bandpass filter of claim 6 , further comprising:
at least a second shunt resonator.

9. The bandpass filter of claim 6 , wherein the first and second series resonators are electrically identical.

10. The bandpass filter of claim 6 , wherein the resonance frequency of the first shunt resonator is proximate to the upper limit of the passband.

11. A bandpass filter comprising:
a plurality of series resonators connected in series between a first port and a second port, the plurality of series resonators including a first series resonator connected between a first node and a second node and a second series resonator connected between the second node and a third node;
a first shunt resonator coupled between the second node and a ground; and
a capacitor connected between the first node and the third node,
wherein a resonance frequency of the first shunt resonator is greater than a resonance frequency of the first and second series resonators.

12. The bandpass filter of claim 11 , wherein the first and second series resonators are electrically identical.

13. The bandpass filter of claim 12 , wherein a capacitance of the capacitor is configured such that a parallel combination of a series combination of the first series resonator and the second series resonator in parallel with the capacitor has an antiresonance frequency lower than an upper limit of a passband of the bandpass filter.

14. The bandpass filter of claim 13 , wherein the capacitance of the capacitor is configured such that the parallel combination significantly sharpens a transition from high transmission to low transmission for frequencies at the upper limit of the passband.

15. The bandpass filter of claim 11 , wherein a resonance frequency of the first shunt resonator is greater than an upper limit of a passband of the bandpass filter.

16. The bandpass filter of claim 15 , wherein the resonance frequency of the first shunt resonator is proximate to the upper limit of the passband.

17. The bandpass filter of claim 11 , wherein a resonance frequency of the first shunt resonator, in isolation, is lower than an upper limit of a passband of the bandpass filter.

18. The bandpass filter of claim 11 , wherein the plurality of series resonators includes at least a third series resonator.

19. The bandpass filter of claim 18 , further comprising:
at least a second shunt resonator.

Assignees

• Murata Manufacturing Co

Inventors

• Jachowski Douglas

Classifications

• H03H9/568

  consisting of a ladder configuration · CPC title

• H03H9/6483

  Ladder SAW filters · CPC title

• H03H9/605

  consisting of a ladder configuration · CPC title

• H03H9/542 Primary

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