Tunable RF filter structure formed by a matrix of weakly coupled resonators

Patent metadata

Field	Value
Publication number	US-9455680-B2
Application number	US-201414298829-A
Country	US
Kind code	B2
Filing date	Jun 6, 2014
Priority date	Jun 6, 2013
Publication date	Sep 27, 2016
Grant date	Sep 27, 2016

Abstract

RF filter structures are disclosed that may have multiple filter paths, which are provided by weakly coupled resonators. The filter paths may be interconnected so that additional filter paths may be realized between input and output terminals of the RF filter structures. In this manner, the weakly coupled resonators from the filter paths may be arranged in a matrix. In one embodiment, an RF filter structure includes a first filter path and a second filter path. The first filter path includes (at least) a first pair of weakly coupled resonators while a second filter path that includes (at least) a second pair of weakly coupled resonators. To interconnect the first filter path and the second filter path, a cross-coupling capacitive structure is electrically connected between the first filter path and the second filter path. As such, an additional filtering path may be realized through the interconnection provided by the cross-coupling capacitive structure.

First claim

What is claimed is:

1. A radio frequency (RF) filter structure, comprising:
a first RF filter path comprising a first pair of coupled resonators that are weakly coupled such that a magnetic coupling coefficient between the first pair of coupled resonators is less than or equal to approximately 0.3, wherein the first pair of coupled resonators comprises a first resonator having a first inductor and a second resonator having a second inductor, wherein the first inductor is coupled to the second inductor such that the magnetic coupling coefficient between the first inductor and the second inductor is less than or equal to approximately 0.3;
a second RF filter path comprising a second pair of coupled resonators that are weakly coupled such that a magnetic coupling coefficient between the second pair of coupled resonators is less than or equal to approximately 0.3, wherein the second pair of coupled resonators comprises a third resonator having a third inductor and a fourth resonator having a fourth inductor, wherein the third inductor is coupled to the fourth inductor such that the magnetic coupling coefficient between the third inductor and the fourth inductor is less than or equal to approximately 0.3; and
a first cross-coupling capacitive structure electrically connected between the first RF filter path and the second RF filter path and the first cross-coupling capacitive structure is electrically connected between the first resonator and the third resonator so as to provide a variable electric coupling coefficient between the first resonator and the third resonator.

2. The RF filter structure of claim 1 wherein the first RF filter path comprises a first plurality of resonators and wherein the first plurality of resonators comprises:
the first pair of coupled resonators; and
one or more first additional resonators.

3. The RF filter structure of claim 2 wherein all of the first plurality of resonators in the first RF filter path are weakly coupled to each other such that the magnetic coupling coefficient between each of the first plurality of resonators is less than or equal to approximately 0.3.

4. The RF filter structure of claim 2 wherein the second RF filter path comprises a second plurality of resonators and wherein the second plurality of resonators comprises:
the second pair of coupled resonators; and
one or more second additional resonators.

5. The RF filter structure of claim 4 wherein:
all of the first plurality of resonators in the first RF filter path are weakly coupled to each other such that the magnetic coupling coefficient between each of the first plurality of resonators is less than or equal to approximately 0.3; and
all of the second plurality of resonators in the second RF filter path are weakly coupled to each other such that the magnetic coupling coefficient between each of the second plurality of resonators is less than or equal to approximately 0.3.

6. The RF filter structure of claim 1 further comprising a unidirectional coupling stage electrically connected within the first RF filter path.

7. The RF filter structure of claim 1 further comprising a unidirectional coupling stage electrically connected between the first RF filter path and the second RF filter path.

8. The RF filter structure of claim 1 wherein
the first RF filter path comprises a first plurality of resonators, and wherein the first plurality of resonators comprises:
the first pair of coupled resonators; and
one or more first additional resonators; and

wherein only a proper subset of the first plurality of resonators is weakly coupled.

9. The RF filter structure of claim 2 wherein at least one of the one or more first additional resonators is weakly coupled to the first pair of coupled resonators such that the magnetic coupling coefficient between each of the at least one of the one or more first additional resonators is less than or equal to approximately 0.3.

10. The RF filter structure of claim 1 further comprising a first input terminal, a second input terminal, and a first output terminal, wherein:
the first RF filter path is electrically connected between the first input terminal and the first output terminal;
the second RF filter path is electrically connected to the second input terminal; and
the first cross-coupling capacitive structure is electrically connected between the first RF filter path and the second RF filter path to define a third RF filter path between the second input terminal and the first output terminal.

11. The RF filter structure of claim 1 further comprising a first input terminal, a first output terminal, and a second output terminal, wherein:
the first RF filter path is electrically connected between the first input terminal and the first output terminal;
the second RF filter path is electrically connected to the second output terminal; and
the first cross-coupling capacitive structure is electrically connected between the first RF filter path and the second RF filter path to define a third RF filter path between the first input terminal and the second output terminal.

12. The RF filter structure of claim 11 further comprising a second input terminal, wherein the second RF filter path is electrically connected between the second input terminal and the second output terminal.

13. The RF filter structure of claim 1 further comprising a second cross-coupling capacitive structure, wherein
the second cross-coupling capacitive structure is electrically connected between the first resonator and the fourth resonator so as to provide a variable electric coupling coefficient between the first resonator and the fourth resonator.

14. The RF filter structure of claim 13 wherein:
the first cross-coupling capacitive structure is a first variable capacitive structure configured to vary the variable electric coupling coefficient between the first resonator and the third resonator; and
the second cross-coupling capacitive structure is a second variable capacitive structure configured to vary the variable electric coupling coefficient between the first resonator and the fourth resonator.

15. The RF filter structure of claim 13 further comprising a third cross-coupling capacitive structure, wherein the third cross-coupling capacitive structure is electrically connected between the first resonator and the second resonator so as to provide a variable electric coupling coefficient between the first resonator and the second resonator.

16. The RF filter structure of claim 15 further comprising a fourth cross-coupling capacitive structure, wherein the fourth cross-coupling capacitive structure is electrically connected between the third resonator and the fourth resonator so as to provide a variable electric coupling coefficient between the third resonator and the fourth resonator.

17. The RF filter structure of claim 16 wherein:
the first cross-coupling capacitive structure is a first variable capacitive structure configured to vary the variable electric coupling coefficient between the first resonator and the third resonator;
the second cross-coupling capacitive structure is a second variable capacitive structure configured to vary the variable electric coupling coefficient between the first resonator and the fourth resonator;
the third cross-coupling capacitive structure is a third variable capacitive structure configured to vary the variable electric coupling coefficient between the first resonator and the second resonator; and
the fourth cross-coupling capacitive structure is a fourth variable capacitive structure configured to vary th

Assignees

• Rf Micro Devices Inc
• Qorvo Us Inc

Inventors

• Leipold Dirk Robert Walter
• Maxim George
• Scott Baker

Classifications

• H10W20/484

  Interconnections having extended contours, e.g. pads having mesh shape or interconnections comprising connected parallel stripes · CPC title

• H03H2210/04

  Filter calibration method · CPC title

• H03H7/1775

  Parallel LC in shunt or branch path (H03H7/1791 takes precedence) · CPC title

• H03F2200/111

  the amplifier being a dual or triple band amplifier, e.g. 900 and 1800 MHz, e.g. switched or not switched, simultaneously or not · CPC title

• H03H7/0115 Primary

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