High-Q integrated RF filters

• US 7,522,017 B1
• Filed: 04/21/2005
• Issued: 04/21/2009
• Est. Priority Date: 04/21/2004
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: Sequoia Communications Corporation
• Inventors: Groe, John, Facchini, Marc
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Glenn, Kimberly E
• Application Number:
  US11/111,680
• Time in Patent Office: 1,461 Days
• Field of Search: None
• US Class Current: 333/175
• CPC Class Codes: H03H 11/44 Negative impedance converters H03H11/42 takes precedence; used in frequency selective networks H03H11/10
• CPC Class Codes: H03H 2007/013 Notch or bandstop filters
• CPC Class Codes: H03H 2210/012 Centre frequency; Cut-off frequency
• CPC Class Codes: H03H 7/0153 Electrical filters; Controlling thereof
• CPC Class Codes: H03H 7/03 comprising means for compensation of loss

Abstract

System for high-Q integrated RF filters. A filter system is provided that comprises a resonate LC filter and a Q-enhancement circuit coupled to the resonate LC filter, wherein the Q-enhancement circuit operates to improve a quality factor of the filter system.

Claims

1. A filter system comprising:

a resonate LC filter; and

a Q-enhancement circuit coupled to the resonate LC filter, wherein the Q-enhancement circuit operates to improve a quality factor of the system and wherein the Q-enhancement circuit comprises a translinear loop that operates to provide an adjustable negative resistance.

2. The filter system of claim 1 further comprising an adjustment circuit coupled to the resonate LC filter to provide tuning.

3. The filter system of claim 2 wherein the adjustment circuit includes a capacitive element distinct from said resonate LC filter.

4. The filter system of claim 3 wherein the capacitive element is a variable capacitive element.

5. The filter system of claim 1 wherein the resonate filter comprises a parallel combination of an inductor and resistor, said resistor distinct from resistance inherent within other components of said resonate filter.

6. The filter system of claim 1 wherein the resonate filter comprises a parallel combination of an inductor and a capacitor.

7. A communications device having an amplifier and a filter system, the filter system comprising:

a resonate LC filter; and

a Q-enhancement circuit coupled to the resonate LC filter, wherein the Q-enhancement circuit operates to improve a quality factor of the system and wherein the Q-enhancement circuit comprises a translinear loop that provides a negative resistance.

8. A filter system, comprising:

a resonate LC filter; and

a Q-enhancement circuit which is coupled to an internal node of said resonate LC filter and which provides an output current which varies oppositely to a voltage at said internal node.

9. The filter system of claim 8, wherein said resonate LC filter includes an output node distinct from said internal node.

10. The filter system of claim 8 further comprising an adjustment circuit coupled to the resonate LC filter to provide tuning.

11. An integrated notch filter system configured to be integrable within a single stage LNA, comprising:

a resonate LC filter; and

a single Q-enhancement circuit coupled to the resonate LC filter, wherein the Q-enhancement circuit operates to improve a quality factor of the system and wherein the Q-enhancement circuit comprises a translinear loop that operates to provide an adjustable negative resistance;

said Q-enhancement circuit further comprising an adjustment circuit coupled to the resonate LC filter to provide tuning, the adjustment circuit including a capacitive element.

12. The notch filter system of claim 11 wherein the capacitive element is distinct from said resonate LC filter.

13. An integrated notch filter system configured to be integrable within a single stage LNA, comprising:

a resonate LC filter; and

a single Q-enhancement circuit coupled to the resonate LC filter, wherein the Q-enhancement circuit operates to improve a quality factor of the system;

said Q-enhancement circuit further comprising an adjustment circuit coupled to the resonate LC filter to provide tuning, the adjustment circuit including a capacitive element; and

wherein the notch filter is configured to be directly connectable to an output of the LNA.

14. The notch filter system of claim 13 wherein the capacitive element is distinct from said resonate LC filter.