Apparatus and method for compensating for analog quadrature modulation error

• US 20050129141A1
• Filed: 11/01/2004
• Published: 06/16/2005
• Est. Priority Date: 10/31/2003
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Seung-Hwan
• Granted Patent: US 7,039,124 B2
• Time in Patent Office: Days
• US Class Current: 375/298
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence

Abstract

An apparatus and method for compensating for an analog quadrature modulation (AQM) error in a linearization apparatus for AQM-modulating a digital predistorted signal and outputting the AQM-modulated signal through a high-power amplifier. In the apparatus and method, a gain/phase error estimator predicts a gain/phase imbalance error caused by AQM on the predistorted signal. A Direct Current (DC) offset estimator predicts a DC offset for a feedback signal from the high-power amplifier. An error compensator compensates for the digital predistorted signal for a DC offset signal output from the DC offset estimator, and then compensates for a gain/phase error output from the gain/phase error estimator.

Claims

1. An apparatus for compensating for an analog quadrature modulation (AQM) error in a linearization apparatus for AQM-modulating a digital predistorted signal and outputting the AQM-modulated signal through a high-power amplifier, the apparatus comprising:

a gain/phase error estimator for predicting a gain/phase imbalance error caused by AQM on the predistorted signal;

a Direct Current (DC) offset estimator for predicting a DC offset for a feedback signal from the high-power amplifier; and

an error compensator for compensating for the digital predistorted signal for a DC offset signal output from the DC offset estimator, and then compensating for a gain/phase error output from the gain/phase error estimator.

2. The apparatus of claim 1, wherein the DC offset estimator predicts a DC offset by calculating an average of the high-power-amplified feedback signals for a predetermined time.

3. The apparatus of claim 1, wherein the error compensator repeats the DC offset compensation a predetermined number of times.

4. The apparatus of claim 1, wherein the error compensator determines a DC offset as ‘

0’

in predicting a gain/phase error.

5. The apparatus of claim 1, wherein the gain/phase error estimator includes a delay estimator for synchronizing the predistorted signal with an AQM feedback signal of the predistorted signal.

6. The apparatus of claim 1, further comprising a comparator for determining a sample for gain/phase error compensation among the digital predistorted signals.

7. The apparatus of claim 6, wherein the comparator determines a predistorted signal having a power level within a predetermined range as a sample on the basis of average output power of the AQM signal.

8. The apparatus of claim 7, wherein the comparator outputs the digital predistorted output sample only to the error compensator when the predistorted signal does not fall within the predetermined range.

9. The apparatus of claim 6, wherein the gain/phase error estimator includes a delay estimator for synchronizing a sample output from the comparator with an AQM feedback sample.

10. The apparatus of claim 9, wherein the gain/phase error estimator acquires a predetermined number of predistorted output samples.

11. The apparatus of claim 1, wherein the error compensator performs gain/phase prediction until the gain/phase error converges into a predetermined value.

12. A method for compensating for an analog quadrature modulation (AQM) error in a linearization apparatus for AQM-modulating a digital predistorted signal and outputting the AQM-modulated signal through a high-power amplifier, the method comprising the steps of:

predicting a Direct Current (DC) offset for a feedback signal from the high-power amplifier;

compensating for the digital predistorted signal for the predicted DC offset;

predicting a gain/phase imbalance error caused by AQM on the predistorted signal; and

compensating for the digital predistorted signal for the gain/phase imbalance error.

13. The method of claim 12, wherein the step of predicting a DC offset comprises the step of predicting a DC offset by calculating an average of the high-power-amplified feedback signals for a predetermined time.

14. The method of claim 12, wherein the step of compensating for the DC offset comprises the step of repeating DC offset compensation a predetermined number of times.

15. The method of claim 12, wherein the step of compensating for a gain/phase error comprises the step of determining a DC offset as ‘

0’

in predicting a gain/phase error.

16. The method of claim 12, further comprising the step of determining a sample for gain/phase error compensation among the digital predistorted signals.

17. The method of claim 16, wherein the step of determining a sample for error compensation comprises the step of determining a predistorted signal having a power level within a predetermined range as a sample on the basis of average output power of the AQM signal.

18. The method of claim 15, wherein the step of predicting a gain/phase error comprises the step of synchronizing the determined sample with an AQM feedback sample.

19. The method of claim 18, wherein the step of predicting a gain/phase error comprises the step of acquiring a predetermined number of predistorted output samples.

20. The method of claim 12, wherein the error compensation step comprises the step of performing gain/phase prediction until the gain/phase error converges into a predetermined value.