SYSTEMS AND METHODS FOR POWER CONTROL IN A MULTIPLE STANDARD MOBILE TRANSMITTER

• US 20120170624A1
• Filed: 12/02/2011
• Published: 07/05/2012
• Est. Priority Date: 12/03/2010
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Rozenblit, Dmitriy, Kahrizi, Masoud, Komaili, Jaleh, Pullela, Rajasekhar, Tadjpour, Shahrzad
• Granted Patent: US 8,874,051 B2
• Time in Patent Office: Days
• US Class Current: 375/219
• CPC Class Codes: H03F 1/0211 with control of the supply voltage or current
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/465 Power sensing
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03F 3/21 with semiconductor devices only H03F3/245 takes precedence
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• 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: H04L 1/0033 arrangements specific to the transmitter

Abstract

A transmitter adjusts a transmitted power level by modifying a control input of a variable gain amplifier. A power amplifier control system includes an envelope extractor, an error extractor, and a feed-forward multiplier. The envelope extractor receives data signal inputs and computes the envelope of the combined signal. The error extractor generates an error signal as a function of the combined signal and the output power generated by the power amplifier. The feed-forward multiplier generates a modified error signal that is responsive to a function of the gain in a feedback path. A corresponding method for controlling a power level is also disclosed. In some embodiments, a transmit chain with a power control loop is used to adjust the transmit signal power applied at an input of a variable gain amplifier. A corresponding method for adjusting the transmit signal power level is also included.

Claims

1. A transmitter having a transmit signal power control system suitable for operating under multiple communication protocols independent of a modulation data envelope, the transmitter comprising:

an envelope extractor coupled to an in-phase digital signal input and a quadrature-phase digital signal input, the envelope extractor configured to compute an instantaneous value of an envelope of a combined data signal at an envelope extractor output;

an error extractor coupled to receive the envelope extractor output and to receive a digital representation of the output power generated by a power amplifier as modified by a feedback multiplier, the error extractor generating an error signal at an extractor output; and

a feed-forward multiplier coupled to the extractor output and configured to generate a modified error signal at a feed-forward multiplier output.

2. The transmitter of claim 1 further comprising a unit converter coupled to the feed-forward multiplier output and configured to generate a digital control signal coupled to a control input of a variable gain amplifier.

3. The transmitter of claim 2 wherein the unit converter performs a linear-to-logarithmic conversion of the modified reference signal.

4. The transmitter of claim 1 wherein the envelope extractor receives the in-phase digital signal input and the quadrature-phase digital signal input from a baseband subsystem and calculates a square root of the sum of the square of the magnitude of the in-phase digital signal and the square of the quadrature-phase digital signal.

5. The transmitter of claim 1 wherein the digital representation of the output power generated by the power amplifier is responsive to a diode detector.

6. The transmitter of claim 1 wherein the digital representation of the output power generated by the power amplifier is responsive to a log detector.

7. The transmitter of claim 1 further comprising a unit converter coupled between the envelope extractor and the error extractor.

8. The transmitter of claim 7 wherein the unit converter performs a linear-to-logarithmic conversion of the instantaneous value of the envelope of the combined data signal.

9. The transmitter of claim 1 wherein the feedback multiplier is responsive to a control input that varies as a function of gain in a feedback path.

10. The transmitter of claim 9 wherein the feed forward multiplier is responsive to a control input that varies as a function of the inverse of the gain in the feedback path.

11. The transmitter of claim 1 further comprising:

a transmit chain having a first stage, a second stage, and a third stage, the transmit chain receiving a baseband in phase data signal and a baseband quadrature phase data signal and generating a transmit signal for application at an input of a power amplifier; and

a transmit chain controller arranged in a closed control loop with the transmit chain.

12. The transmitter of claim 11 wherein the first stage includes a first path and a second path, the first path and the second path each including respective digital-to-analog converters, low-pass filters, and modulators, one of the first path and the second path configured to provide a first range of gain control and the other path configured to provide a second range of gain control different from the first range of gain control.

13. The transmitter of claim 12 wherein the modulators provide approximately 6 dB of gain control.

14. The transmitter of claim 11 wherein the second stage includes a digitally-controlled step attenuator that provides approximately 32 dB of gain control.

15. The transmitter of claim 11 wherein the third stage includes a digitally-controlled discrete gain-step amplifier that provides approximately 32 dB of gain control.

16. The transmitter of claim 11 wherein the transmit chain controller receives indicators of the transmit signal power from respective locations in the transmit chain.

17. The transmitter of claim 16 wherein the transmit chain controller includes an error estimator coupled to a logic element and a gain adjuster, the logic element generating a plurality of first gain control signals selectively distributed across the second stage and the third stage, the gain adjuster applying a factor responsive to the gain step change in the transmit chain to generate a second gain control signal suitable for adjusting the digital-to-analog converters in the first stage.

18. A method for accurately controlling an adjustable power level in a transmitter that is transmitting a data signal with a time-varying signal envelope, the method, comprising:

determining, in an envelope extractor, an instantaneous representation of the data signal envelope;

generating a scaled representation of the power at an output of a power amplifier;

generating an error signal as a function of both the instantaneous representation of the data signal envelope and the scaled representation of the power at the output of the power amplifier; and

modifying the error signal as a function of the gain in a feedback path to generate a modified error signal.

19. The method of claim 18 wherein when a log power detector is used to monitor the output power of the power amplifier, the method further comprises:

modifying the scaled representation of the power at the output of the power amplifier with a multiplier to generate a gain adjusted representation of the output of the power amplifier; and

using a unit converter to adjust the instantaneous representation of the data signal envelope.

20. The method of claim 18 wherein when a linear power detector is used to monitor the output power of the power amplifier, the method further comprises:

modifying the representation of the output of the power amplifier with a multiplier; and

using a unit converter to adjust the modified error signal to generate a power control signal.

21. A method for accurately controlling an adjustable power level of a data signal in a transmit chain of a transmitter, the method, comprising:

adjusting a controllable gain level of a digital-to-analog converter based on a desired peak-to-average ratio of a transmit signal envelope;

adjusting a digitally controlled discrete gain-step amplifier, the amount of gain per step based on an initial estimate of the transmitter gain and a target power;

applying a factor to a gain adjuster responsive to the gain step change in the transmit chain; and

repeating the adjusting and applying steps until a feedback signal level exceeds a reference signal level.

22. The method of claim 21 further comprising:

storing a value representing the feedback gain control being applied when the feedback signal level exceeds the reference signal level; and

applying the value.

23. A signal power control system comprising:

a reference generator implemented to receive and combine an in-phase digital signal and a quadrature-phase digital signal so as to yield a combined signal, the reference generator further implemented to generate an output signal representative of an instantaneous value of an envelope of the combined signal;

an error extractor implemented to receive a first input signal including the output signal of the envelope extractor and a second input signal including a digital representation of an output of a power amplifier, the error extractor further implemented to generate an error signal based on the first and second input signals; and

a control signal generator implemented to receive the error signal and generate one or more control signals for controlling a gain of an analog section of a transmit chain that provides a modulated analog signal to the power amplifier so as to substantially cancel a modulation envelope associated with the modulated analog signal.

24. The system of claim 23 wherein the power control system includes a transmit signal power control system.

25. The system of claim 24 wherein the reference generator includes an envelope extractor configured to receive and combine the in-phase and quadrature-phase digital signals and generate the instantaneous value of the envelope of the combined signal.

26. The system of claim 24 wherein the control signal generator includes an error estimator and a logic element configured to quantify the magnitude of the error signal and generate a coarse power control signal and an adjustment signal.

27. The system of claim 26 wherein the control signal generator further includes a multiplier configured to receive as inputs the error signal and a sum of the adjustment signal from the logic element and an inverse of a feedback-path gain factor, the control signal generator further configured to generate a fine power control signal that reduces undesired changes in loop gain of a power control loop.

28. The system of claim 27 wherein the fine power control signal includes a product of the inputs.

29. The system of claim 28 wherein the control signal generator further includes a digital adder configured to receive and add the adjustment signal from the logic element and the inverse of a feedback-path gain factor, the digital adder further configured to provide the sum to the multiplier.

30. The system of claim 28 wherein the control signal generator further includes a low-pass filter configured to remove or filter the fine power control signal.

31. The system of claim 24 wherein the transmit signal power control system is configured to operate under a plurality of communication modes.

32. The system of claim 31 wherein the communication modes include WCDMA/LTE communication modes.

33. The system of claim 31 wherein the communication modes include EDGE/GMSK communication modes.

34. The system of claim 33 wherein the reference generator includes a unit converter configured to receive the instantaneous value of the envelope and generate a converted value representative of the instantaneous value, the unit converter further configured to forward to the converted value to the error extractor.

35. The system of claim 34 wherein the unit converter includes a log converter configured to perform a linear-to-logarithmic conversion.

36. The system of claim 33 wherein the control signal generator includes a unit converter configured to receive at least one of the one or more control signals and generate a converted value.

37. The system of claim 36 wherein the at least one control signal includes a fine power control signal.

38. The system of claim 37 wherein the unit converter includes a log converter configured to perform a linear-to-logarithmic conversion.

39. A transmitter module for a wireless device, the module comprising:

a packaging substrate;

a semiconductor die mounted on the packaging substrate, the semiconductor die having an integrated circuit configured to provide power control for transmitted signal, the integrated circuit including a reference generator implemented to receive and combine an in-phase digital signal and a quadrature-phase digital signal so as to yield a combined signal, the reference generator further implemented to generate an output signal representative of an instantaneous value of an envelope of the combined signal;

an error extractor implemented to receive a first input signal including the output signal of the envelope extractor and a second input signal including a digital representation of an output of a power amplifier, the error extractor further implemented to generate an error signal based on the first and second input signals; and

a control signal generator implemented to receive the error signal and generate one or more control signals for controlling a gain of an analog section of a transmit chain that provides a modulated analog signal to the power amplifier so as to substantially cancel a modulation envelope associated with the modulated analog signal; and

a packaging structure configured to provide protection for the mounted semiconductor die.

40. The module of claim 39 wherein the transmitter module is a part of a transceiver module.

41. A wireless device comprising:

an antenna configured to facilitate receiving and sending of radio-frequency (RF) signals;

a receiver circuit configured to process an RF signal received from the antenna;

a transmitter circuit configured to process an RF signal to be provided to the antenna, the transmitter circuit including an integrated circuit configured to provide power control for transmitted signal, the integrated circuit including a reference generator implemented to receive and combine an in-phase digital signal and a quadrature-phase digital signal so as to yield a combined signal, the reference generator further implemented to generate an output signal representative of an instantaneous value of an envelope of the combined signal;

an error extractor implemented to receive a first input signal including the output signal of the envelope extractor and a second input signal including a digital representation of an output of a power amplifier, the error extractor further implemented to generate an error signal based on the first and second input signals; and

a control signal generator implemented to receive the error signal and generate one or more control signals for controlling a gain of an analog section of a transmit chain that provides a modulated analog signal to the power amplifier so as to substantially cancel a modulation envelope associated with the modulated analog signal; and

a baseband subsystem configured to provide control signals for operation of the receiver and transmitter circuits.

42. The wireless device of claim 41 wherein the wireless device is configured to operate under a plurality of communication modes.

43. The wireless device of claim 41 wherein the communication modes include WCDMA/LTE modes and EDGE/GMSK modes.

44. A transmit signal power control system for a wireless device, the system comprising:

a transmit signal path having a transmit chain and one or more power amplifiers, the transmit chain configured to receive a digital input signal and generate a modulated analog signal as an input for the one or more power amplifiers, the transmit chain including an analog section configured to provide variable gain for the modulated analog signal; and

a control loop configured to generate one or more control signals for adjusting the variable gain of the analog section of the transmit chain based on a digital representation of an output of the one or more power amplifiers and the digital input signal, such that the transmit power control system is responsive to a gain change but substantially non-responsive to a modulation change.

45. The system of claim 44 wherein the control loop is configured so as to substantially cancel a modulation envelope associated with the modulated analog signal.

46. The system of claim 45 wherein the substantially non-responsiveness to the modulation change allows the transmit signal power control system to operate under different communication protocols substantially independent of the modulation envelope.

47. A method for controlling power of a radio-frequency (RF) signal in a wireless device, the method comprising:

generating a modulated analog signal based on a digital input signal;

amplifying the modulated analog signal so as to yield an output signal;

generating, by a control loop, a control signal for adjusting a gain associated with the modulated analog signal based on a digital representation of the output signal and the digital input signal; and

adjusting the gain associated with the modulated analog signal, such that the adjusted modulated analog signal is substantially non-responsive to a modulation change.

48. The method of claim 47 wherein the adjusted modulated analog signal is responsive to a gain change.

49. The method of claim 48 wherein the generating of the control signal is performed so as to substantially cancel a modulation envelope associated with the modulated analog signal.

50. The method of claim 49 wherein the substantially non-responsiveness to the modulation change allows the controlling of power to be performed under different communication protocols substantially independent of the modulation envelope.