Closed Loop Power Control for a Wireless Transmitter

• US 20120270511A1
• Filed: 04/20/2012
• Published: 10/25/2012
• Est. Priority Date: 04/22/2011
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Mostafa, Mohamed, Shaeffer, Derek, DAKSHINAMURTHY, Sriraman, Pu, Dennis, Capofreddi, Peter
• Granted Patent: US 8,774,738 B2
• Time in Patent Office: Days
• US Class Current: 455/115.1
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H04B 17/13 of power amplifiers, e.g. gain or non-linearity

Abstract

Embodiments of the present disclosure provide systems and methods for estimating gain and phase error in a wireless transmitter. Embodiments of the present disclosure provide a gain and phase controller that uses a digital gain and phase estimator to jointly estimate both gain and phase. The forward and feedback signals of a wireless transmitter are digitized using analog to digital (ADC) converters. The digital signals are correlated with each other to dynamically extract gain and phase estimates of the loop. The gain and phase estimates are used to correct gain and phase errors in the wireless transmitter.

Claims

9. A controller comprising:

a correlation module configured to receive a forward sample of a forward signal transmitted to an output port of a wireless transmitter and a feedback sample from a feedback mechanism of the wireless transmitter;

a mean computation module configured to receive the forward sample and the feedback sample; and

an impairment computation module coupled to an output of the correlation module, wherein the impairment computation module is configured to compute an estimated impairment value representing impairments introduced into a feedback loop of a host circuit coupled to the controller.

1. A wireless transmitter comprising:

an output port;

a feedback mechanism coupled to the output port; and

a controller configured to receive a forward sample of a forward signal transmitted to the output port and a feedback sample from the feedback mechanism, wherein the controller comprises an estimator, and wherein the estimator comprises;

a correlation module configured to receive the forward sample and the feedback sample, and

an impairment computation module coupled to an output of the correlation module, wherein the impairment computation module is configured to compute an estimated gain error and an estimated phase error.

2. The wireless transmitter of claim 1, wherein the wireless transmitter further comprises:

a power amplifier coupled to the output port; and

a filter coupled to an input of the power amplifier.

3. The wireless transmitter of claim 2, wherein the controller is configured to adjust a value of the power amplifier based on the estimated gain error.

4. The wireless transmitter of claim 2 wherein the controller is configured to adjust the wireless transmitter based on the estimated phase error.

5. The wireless transmitter of claim 1, further comprising a programmable delay element coupled to an input of the correlation module and the mean module.

6. The wireless transmitter of claim 1, wherein the estimator further comprises:

a mean module configured to receive the forward sample and the feedback sample; and

a combination module coupled to an output of the correlation module, an output of the mean module, and an input of the impairment computation module.

7. The wireless transmitter of claim 1, further comprising:

a directional coupler coupled to the output port, wherein the directional coupler is configured to obtain the feedback sample;

a feedback attenuator coupled to the directional coupler; and

a mixer coupled to an output of the feedback attenuator, wherein the mixer is configured to provide an input to the controller.

8. The wireless transmitter of claim 1, wherein the wireless transmitter includes a Cartesian Feedback Loop (CFL).

10. The controller of claim 9, wherein the correlation module is configured to compute a cross-correlation between the feedback sample and the forward sample.

11. The controller of claim 9, wherein the correlation module is further configured to compute a self-correlation using the forward sample.

12. The controller of claim 11, wherein the parameter estimate computation module is farther configured to compute a gain mismatch error and a quadrature error.

13. The controller of claim 11, wherein the controller is configured to select either an accurate method for computing the gain estimate and the phase estimate or an approximate method for computing the gain estimate and the phase estimate.

14. The controller of claim 13, wherein the controller is configured to select either the accurate method or the approximate method based on a determinant value of a self-correlation matrix computed from the forward sample.

10-1. The controller of claim 9, further comprising:

a combination module coupled to an output of the correlation module, an output of the mean computation module, and an input of the impairment computation module, wherein the combination module is configured to combine information output from the mean module and the correlation module.

11-2. The controller of claim 10, further comprising a parameter estimate computation module coupled to an output of the impairment computation module, wherein the parameter estimate computation module is configured to compute a gain estimate and a phase estimate based on the estimated impairment value, and wherein the controller is configured to adjust the wireless transmitter based on the gain estimate and the phase estimate.

15. A method comprising:

receiving a forward sample of a forward signal transmitted to an output port of a wireless transmitter and a feedback sample from a feedback mechanism of the wireless transmitter;

computing an estimated impairment value representing impairments introduced into a feedback loop of a host circuit, wherein the impairments include a gain error and a phase error; and

adjusting the feedback loop based on the estimated impairment value.

16. The method of claim 15, further comprising:

calculating a cross-correlation result between the forward sample and the feedback sample; and

calculating a self-correlation result using the forward sample.

17. The method of claim 16, further comprising:

subtracting a first direct current (DC) offset component of the cross-correlation result; and

subtracting a second direct current (DC) offset component of the self-correlation result.

18. The method of claim 16, further comprising:

computing a determinant of the self-correlation result; and

selecting an accurate method for computing a gain estimate and a phase estimate or an approximate method for computing a gain estimate and a phase estimate based on the determinant.

19. The method of claim 15, further comprising:

averaging forward sample with a plurality of additional forward samples; and

averaging the feedback sample with a plurality of additional feedback samples.

20. The method of claim 15, wherein the estimated impairment value is an estimated impairment matrix.