Closed loop power control for a wireless transmitter
View Patent ↗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.
1. A wireless transmitter comprising:
an output port;
a feedback mechanism coupled to the output port, wherein the feedback mechanism is configured to generate a feedback signal; and
a controller configured to:
receive a forward sample of a forward signal transmitted to the output port, and
receive a feedback sample of the feedback signal from the feedback mechanism,
wherein the controller comprises an estimator, and wherein the estimator comprises:
a correlation module configured to correlate 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 representing a difference in gain between the forward signal and the feedback signal, and
compute an estimated phase error representing a difference in phase between the forward signal and the feedback signal.
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 further 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 further 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 a 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 the 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).
9. A controller comprising:
a correlation module configured to:
correlate a forward sample of a forward signal transmitted to an output port of a wireless transmitter, and
correlate a feedback sample of a feedback signal generated by a feedback mechanism of the wireless transmitter;
a mean 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 estimated impairments introduced into a feedback loop of a host circuit coupled to the controller, and wherein the estimated impairments include an estimated phase error representing a difference in phase between the forward signal and the feedback signal.
10. The controller of claim 9 , wherein the correlation module is further configured to compute a cross-correlation between the feedback sample and the forward sample.
11. 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 module configured to receive the forward sample and the feedback sample;
a combination module coupled to an output of the correlation module and to an output of the mean module, wherein the combination module is configured to combine information output from the mean module and the correlation module; and
an impairment computation module coupled to an output of the combination 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.
12. The controller of claim 9 , farther 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 an estimated gain error and the estimated phase error based on the estimated impairments, and wherein the controller is configured to adjust the wireless transmitter based on the estimated gain error and the estimated phase error.
13. The controller of claim 12 , wherein the parameter estimate computation module is further configured to compute a gain mismatch error and a quadrature error.
14. The controller of claim 12 , wherein the controller is further configured to select either an accurate method for computing the estimated gain error and the estimated phase error or an approximate method for computing the estimated gain error and the estimated phase error.
15. The controller of claim 14 , wherein the controller is further 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.
16. A method comprising:
receiving a forward sample of a forward signal transmitted to an output port of a wireless transmitter;
receiving a feedback sample of a feedback signal from a feedback mechanism of the wireless transmitter;
correlating, using a correlation module, the forward sample and the feedback sample to generate correlated data;
computing, based on the correlated data, estimated impairments introduced into a feedback loop of a host circuit, wherein the estimated impairments include:
an estimated gain error representing a difference in gain between the forward signal and the feedback signal, and
an estimated phase error representing a difference in phase between the forward signal and the feedback signal; and
adjusting the feedback loop based on the estimated impairments.
17. The method of claim 16 , 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.
18. The method of claim 17 , 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.
19. The method of claim 17 , further comprising:
computing a determinant of the self-correlation result; and
selecting an accurate method for computing the estimated impairments or an approximate method for computing the estimated impairments based on the determinant.
20. The method of claim 16 , further comprising:
averaging the forward sample with a plurality of additional forward samples; and
averaging the feedback sample with a plurality of additional feedback samples.
21. The method of claim 16 , further comprising:
computing an estimated impairment matrix to compute the estimated impairments.
22. The wireless transmitter of claim 1 , wherein the estimator is a digital gain and phase estimator configured to jointly compute the estimated gain error and the estimated phase error.