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

• US 9,455,680 B2
• Filed: 06/06/2014
• Issued: 09/27/2016
• Est. Priority Date: 06/06/2013
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Inventors: Leipold, Dirk Robert Walter, Maxim, George, Scott, Baker
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): PATEL, RAKESH BHASKARBHAI
• Application Number:
  US14/298,829
• Publication Number:
  US 20140361848A1
• Time in Patent Office: 844 Days
• Field of Search: 333/174, 333/175, 333/185
• US Class Current: 1/1
• CPC Class Codes: H01L 23/4824 Pads with extended contours, e.g. grid structure, branch structure, finger structure
• CPC Class Codes: H03F 1/565 using inductive elements
• CPC Class Codes: H03F 2200/111 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 Class Codes: H03F 2200/267 A capacitor based passive circuit, e.g. filter, being used in an amplifying circuit
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2203/7209 the gated amplifier being switched from a first band to a second band
• CPC Class Codes: H03F 3/193 with field-effect devices H03F3/195 takes precedence
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H03F 3/68 Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602
• CPC Class Codes: H03F 3/72 Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal
• CPC Class Codes: H03H 2210/012 Centre frequency; Cut-off frequency
• CPC Class Codes: H03H 2210/025 Capacitor
• CPC Class Codes: H03H 2210/04 Filter calibration method
• CPC Class Codes: H03H 7/0115 comprising only inductors and capacitors H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence
• CPC Class Codes: H03H 7/0153 Electrical filters; Controlling thereof
• CPC Class Codes: H03H 7/09 Filters comprising mutual inductance
• CPC Class Codes: H03H 7/1775 Parallel LC in shunt or branch path H03H7/1791 takes precedence
• CPC Class Codes: H03H 7/46 Networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source for use in multiplex transmission systems H04J1/00
• CPC Class Codes: H03H 7/463 Duplexers
• CPC Class Codes: H03H 7/465 having variable circuit topology, e.g. including switches
• CPC Class Codes: H04B 1/1027 : assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/18 : Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H

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.

Claims

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 the variable electric coupling coefficient between the third resonator and the fourth resonator.

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

19. The RF filter structure of claim 18 further comprising a sixth cross-coupling capacitive structure, wherein the sixth 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 second resonator and the third resonator.

20. The RF filter structure of claim 19 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;

the fourth cross-coupling capacitive structure is a fourth variable capacitive structure configured to vary the variable electric coupling coefficient between the third resonator and the fourth resonator;

the fifth cross-coupling capacitive structure is a fifth variable capacitive structure configured to vary the variable electric coupling coefficient between the second resonator and the fourth resonator; and

the sixth cross-coupling capacitive structure is a sixth variable capacitive structure configured to vary the variable electric coupling coefficient between the second resonator and the fourth resonator.

21. The RF filter structure of claim 1 further comprising:

a first input terminal;

a first output terminal, wherein the first RF filter path is electrically connected between the first input terminal and the first output terminal;

a second input terminal; and

a second output terminal, wherein the second RF filter path is electrically connected between the second input terminal and the second output terminal.

22. The RF filter structure of claim 21 further comprising:

a third RF filter path comprising a third pair of coupled resonators that are weakly coupled such that a magnetic coupling coefficient between the third pair of coupled resonators is less than or equal to approximately 0.3;

a third input terminal; and

a third output terminal, wherein the third RF filter path is electrically connected between the third input terminal and the third output terminal.

23. The RF filter structure of claim 22 further comprising a third cross-coupling capacitive structure, wherein the third cross-coupling capacitive structure is electrically connected between the second RF filter path and the third RF filter path.

24. The RF filter structure of claim 23 wherein:

the first cross-coupling capacitive structure is a first variable capacitive structure; and

the third cross-coupling capacitive structure is a third variable capacitive structure.