Internal calibration system for a radio frequency (RF) transmitter

• US 20060252392A1
• Filed: 04/06/2005
• Published: 11/09/2006
• Est. Priority Date: 04/06/2005
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Domino, William J., Damgaard, Morten, Beamish, Norman J.
• Granted Patent: US 7,647,028 B2
• Time in Patent Office: Days
• US Class Current: 455/126
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H04B 17/101 for measurement of specific parameters of the transmitter or components thereof
• CPC Class Codes: H04B 17/14 of the whole transmission and reception path, e.g. self-test loop-back
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements

Abstract

An internal calibration system for a radio frequency (RF) transmitter comprises a digital processing element to generate within a radio frequency (RF) transmitter test points at which an output of the RF transmitter is measured, an RF detector to measure the radio frequency output of the RF transmitter at the test points, the digital processing element also determining transmitter impairments by analyzing the measured radio frequency output, and compensation circuitry to compensate the RF transmitter for the measured impairments.

Claims

1. A method for internally calibrating a radio frequency (RF) transmitter, comprising:

generating within a radio frequency (RF) transmitter test points at which an output of the RF transmitter is measured;

measuring the radio frequency output of the RF transmitter at the test points;

determining transmitter impairments by analyzing the measured radio frequency output; and

compensating for the measured impairments.

2. The method of claim 1, further comprising measuring the radio frequency output of the RF transmitter using an energy detector.

3. The method of claim 2, further comprising generating the test points using a transmitter output scaled by a scaling factor.

4. The method of claim 3, wherein the transmitter impairments comprise at least one of gain imbalance, phase imbalance and direct current (DC) offset for in-phase and quadrature components of the radio frequency output.

5. The method of claim 4, further comprising calculating a phase imbalance and a quadrature DC offset of the radio frequency output by estimating the impairments using six test points.

6. The method of claim 5, further comprising calculating a gain imbalance of the radio frequency output by estimating the impairments using four test points.

7. The method of claim 6, further comprising calculating an in-phase DC offset of the radio frequency output by estimating the impairments using two test points.

8. The method of claim 3, wherein the scaling factor is unity.

9. The method of claim 1, further comprising measuring the radio frequency output of the RF transmitter using an envelope detector.

10. The method of claim 9, wherein the transmitter impairments comprise at least one of gain imbalance, phase imbalance and direct current (DC) offset for in-phase and quadrature components of the radio frequency output.

11. The method of claim 10, further comprising defining at least one function representing an output of the envelope detector.

12. The method of claim 11, further comprising varying the function to minimize a range between which the function is minimized.

13. The method of claim 12, wherein minimizing the function yields an estimate for the gain imbalance, phase imbalance and the DC offset for the in-phase and quadrature components of the radio frequency output.

14. The method of claim 13, further comprising using the estimate to substantially reduce the gain imbalance, phase imbalance and the DC offset for the in-phase and quadrature components of the radio frequency output.

15. An internal calibration system for a radio frequency (RF) transmitter, comprising:

a digital processing element to generate within a radio frequency (RF) transmitter test points at which an output of the RF transmitter is measured;

an RF detector to measure the radio frequency output of the RF transmitter at the test points, the digital processing element also determining transmitter impairments by analyzing the measured radio frequency output; and

compensation circuitry to compensate the RF transmitter for the measured impairments.

16. The system of claim 15, wherein the RF detector is implemented using an energy detector.

17. The system of claim 16, wherein the digital processing element generates the test points using a transmitter output scaled by a scaling factor.

18. The system of claim 17, wherein the transmitter impairments comprise at least one of gain imbalance, phase imbalance and direct current (DC) offset for in-phase and quadrature components of the radio frequency output.

19. The system of claim 18, wherein the digital processing element calculates a phase imbalance and a quadrature DC offset of the radio frequency output by estimating the impairments using six test points.

20. The system of claim 19, wherein the digital processing element calculates a gain imbalance of the radio frequency output by estimating the impairments using four test points.

21. The system of claim 20, wherein the digital processing element calculates an in-phase DC offset of the radio frequency output by estimating the impairments using two test points.

22. The system of claim 17, wherein the scaling factor is unity.

23. The system of claim 15, wherein the RF detector is implemented using an envelope detector.

24. The system of claim 23, wherein the transmitter impairments comprise at least one of gain imbalance, phase imbalance and direct current (DC) offset for in-phase and quadrature components of the radio frequency output.

25. The system of claim 24, further comprising defining at least one function representing an output of the envelope detector.

26. The system of claim 25, wherein the digital processing element varies the function to minimize a range between which the function is minimized.

27. The system of claim 26, wherein the digital processing element yields an estimate for the gain imbalance, phase imbalance and the DC offset for the in-phase and quadrature components of the radio frequency output.

28. The system of claim 27, wherein the compensation circuitry uses the estimate to substantially reduce the gain imbalance, phase imbalance and the DC offset for the in-phase and quadrature components of the radio frequency output.

29. A portable transceiver having an internal calibration system for a radio frequency (RF) transmitter, comprising:

transmit and receive circuitry;

a digital processing element to generate within a radio frequency (RF) transmitter test points at which an output of the RF transmitter is measured;

an RF detector to measure the radio frequency output of the RF transmitter at the test points, the digital processing element also determining transmitter impairments by analyzing the measured radio frequency output; and

compensation circuitry to compensate the RF transmitter for the measured impairments.

30. A system for internally calibrating a radio frequency (RF) transmitter, comprising:

means for generating within a radio frequency (RF) transmitter test points at which an output of the RF transmitter is measured;

means for measuring the radio frequency output of the RF transmitter at the test points;

means for determining transmitter impairments by analyzing the measured radio frequency output; and

means for compensating for the measured impairments.