System and method for power control calibration and a wireless communication device

• US 20030002452A1
• Filed: 06/20/2002
• Published: 01/02/2003
• Est. Priority Date: 06/26/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sahota, Gurkanwal Singh
• Granted Patent: US 6,819,938 B2
• Time in Patent Office: Days
• US Class Current: 370/318
• CPC Class Codes: H04B 17/13 of power amplifiers, e.g. gain or non-linearity
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

A technique for calibrating the open-loop transmit power of a wireless communication device overcomes the inherent nonlinearities in the gain control input of a variable gain amplifier (VGA). In one embodiment, a feedback circuit generates a signal indicative of the transmit power. This signal is compared with a desired transmit power level, which comprises an open-loop gain component and a closed-loop gain component. The desired transmit power level is compared with the actual transmit power level and an error signal is generated. The error signal is used to alter the gain of the VGA in the transmitter to thereby adjust the actual transmit power level to correspond with the desired transmit power level. In alternative embodiment, the receiver portion, which also contains a VGA, is pre-calibrated in a conventional manner. During a transmitter calibration process, the transmitter is coupled to the receiver input through a mixer and filter. The pre-calibrated receiver determines the actual transmit power level. The difference is used to generate error correction data to adjust for non linearities in the gain control input of the transmitter VGA.

Claims

1. A system for the control of transmit power in a wireless communication device having a transmitter and a receiver, the system comprising:

a power control reference circuit to generate a power control signal indicative of a desired transmit power;

a variable gain transmitter amplifier having an amplifier input and an amplifier output and a variable gain control input;

a transmit power control circuit to generate a control signal coupled to the control input to thereby control the variable gain;

a transmit power processor coupled to the amplifier output to detect a transmit power level and to generate a feedback signal related thereto; and

a summing circuit to combine the feedback signal and power control signal wherein the combined feedback and power control signal are provided as an input to the power control circuit.

2. The system of claim 1, further comprising a received signal strength circuit to generate a received signal strength indicator indicative of a received signal strength of a radio signal received by the receiver, the power control signal comprising the received signal strength indicator.

3. The system of claim 2, further comprising an open loop power reference signal based on the received signal strength indicator and a predetermined additional power gain, the power control signal comprising the predetermined additional power gain.

4. The system of claim 2, further comprising a closed loop power reference signal based a power control command received by the receiver, the power control signal comprising the closed loop power reference signal.

5. The system of claim 1 wherein the wireless communication device includes an antenna, the system further comprising a radio frequency (RF) amplifier having an RF amplifier input, an RF amplifier output and an RF amplifier gain control input, the RF amplifier output being coupled to the antenna and the RF amplifier gain input being coupled to the and receiving the control signal therefrom.

6. The system of claim 5 wherein the RF amplifier is incrementally controlled in gain steps and the transmit power control circuit generates step control signals, the step control signals being provided to the RF amplifier gain input to thereby control the step gain of the RF amplifier.

7. The system of claim 1 wherein the transmit power control circuit comprises a digital-to-analog converter to convert the combined feedback and power control signal into an analog signal, the analog signal being coupled to the control input.

8. The system of claim 1 wherein the transmit power processor comprises a log circuit to generate the feedback signal in logarithmic form and thereby control the gain of the variable gain transmitter amplifier in decibels.

9. The system of claim 1 the system further comprising a transmit power control circuit coupled to the error circuit, the transmit power control circuit comprising a log circuit to generate the error signal in logarithmic form and thereby control the gain of the variable gain transmitter amplifier in decibels.

10. A system for the control of transmit power in a wireless communication device having a transmitter and a receiver, the system comprising:

a variable gain transmitter amplifier having an amplifier input and an amplifier output and a variable gain control input;

a power control reference circuit to generate a power control signal indicative of a desired transmit power, the power control signal having an open-loop gain component and a closed-loop gain component;

a transmit power processor coupled to the amplifier output to detect a transmit power level and to generate a feedback signal related thereto; and

an error circuit to compare the feedback signal and power control signal and generated an error signal based thereon, the error signal being coupled to the power control circuit.

11. The system of claim 10, further comprising a received signal strength circuit to generate a received signal strength indicator indicative of a received signal strength of a radio signal received by the receiver, the open-loop gain component being based, at least in part, on the received signal strength indicator.

12. The system of claim 11 wherein the open-loop gain component further comprises a predetermined additional power gain, the open-loop gain component comprising the received signal strength indicator and the predetermined additional power gain.

13. The system of claim 10 wherein the closed-loop gain component is based a power control command received by the receiver.

14. The system of claim 10 wherein the wireless communication device includes an antenna, the system further comprising a radio frequency (RF) amplifier having an RF amplifier input, an RF amplifier output and an RF amplifier gain control input, the RF amplifier output being coupled to the antenna and the RF amplifier gain input being configured to receive the error signal.

15. The system of claim 14 wherein the RF amplifier is incrementally controlled in gain steps, the system further comprising a transmit power control circuit configured to receive the error signal and generate step control signals, based on the error signal, the step control signals being provided to the RF amplifier gain input to thereby control the step gain of the RF amplifier.

16. The system of claim 10 wherein the transmit power processor comprises a log circuit to generate the feedback signal in logarithmic form and thereby control the gain of the variable gain transmitter amplifier in decibels.

17. The system of claim 10 the system further comprising a transmit power control circuit coupled to the error circuit, the transmit power control circuit comprising a log circuit to generate the error signal in logarithmic form and thereby control the gain of the variable gain transmitter amplifier in decibels.

19. The system of claim 18, further comprising a linearizer containing linearization data indicative of a difference between the control signal indicative of the desired transmit power level and the power measured using the calibrated receiver signal pathway.

20. The system of claim 18 wherein the coupling circuit comprises a switch to couple the signal generated by the mixer to the receiver signal pathway.

21. The system of claim 18 wherein the receiver signal pathway comprises an intermediate frequency (IF) stage coupled to a demodulator stage, the coupling circuit coupling the signal generated by the mixer to the receiver signal pathway following the IF stage.

22. The system of claim 21, further comprising a bandpass filter intermediate the mixer and the coupling circuit to provide IF filtering.

23. The system of claim 18 wherein the oscillator frequency is selected to permit the signal generated by the mixer to match an intermediate frequency (IF) of the receiver.

24. The system of claim 18 wherein the coupling circuit comprises a single-pole-single-throw (SPST) type switch to couple the signal generated by the mixer to the receiver signal pathway

25. The system of claim 24 wherein the receiver comprises a first receiver variable gain amplifier in the receiver signal pathway, the system further comprising a second receiver variable gain amplifier having an input coupled to the SPST type switch and an output coupled to the receiver signal pathway to couple the signal generated by the mixer to the receiver signal pathway.

26. The system of claim 25 wherein the first and second receiver variable gain amplifiers are matched circuits implemented on a common integrated circuit.

27. The system of claim 25 wherein the first receiver variable gain amplifier has an output, the system further comprising a summer having first and second summer inputs and a summer output with the first and second receiver variable gain amplifier outputs being coupled to the first and second summer inputs, respectively, the summer output being a portion of the receiver signal pathway.

28. The system of claim 23 wherein the wireless communication device has a transmitter calibration mode, the coupling circuit being selected activated when in the transmitter calibration mode to permit the signal generated by the mixer to be coupled to the receiver signal pathway.

29. The system of claim 18 wherein the coupling circuit comprises a single-pole-double-throw (SPDT) type switch to couple the signal generated by the mixer to the receiver signal pathway.

30. The system of claim 29 wherein the receiver comprises a receiver variable gain amplifier in the receiver signal pathway, the SPDT type switch having a first terminal coupled to the output of the mixer to receiver the signal generated by the mixer, a second terminal coupled to a radio frequency (RF) stage of the receiver and a switch common terminal coupled to the receiver signal pathway.

31. The system of claim 30 wherein the second terminal is coupled to the RF stage via an intermediate frequency (IF) stage wherein the oscillator frequency is selected to permit the signal generated by the mixer to match an intermediate frequency (IF) of the receiver.

18. A system for the control of transmit power in a wireless communication device having a transmitter and a receiver, the receiver having a calibrated receiver signal pathway capable of determining the strength of a received signal, the system comprising:

a variable gain radio frequency (RF) transmitter amplifier having an amplifier input and an amplifier output and a variable gain control input, the variable gain control input initially receiving a control signal indicative of a desired transmit power level;

a mixer coupled to the amplifier output and receiving a local oscillator signal having an oscillator frequency corresponding to an operational frequency of the receiver, the mixer generating a signal at operational frequency of the receiver and corresponding to a signal at the amplifier output; and

a coupling circuit to couple the signal generated by the mixer to the receiver signal pathway to permit power measurement of the signal using the calibrated receiver signal pathway.

32. A method for the control of transmit power in a wireless communication device having a transmitter and a receiver, the method comprising:

generating a power control signal indicative of a desired transmit power, the power control signal having an open-loop gain component and a closed-loop gain component;

coupling the power control signal to a gain control input of a variable gain transmitter amplifier having an amplifier input and an amplifier output;

detecting a transmit power level at the amplifier output and generating a feedback signal related thereto; and

comparing the feedback signal and power control signal and generating an error signal based thereon, the error signal being used to generate the power control signal.

33. The method of claim 32 wherein the receiver generates a received signal strength indicator indicative of a received signal strength of a radio signal received by the receiver, the open-loop gain component being based, at least in part, on the received signal strength indicator.

34. The method of claim 32 wherein the open-loop gain component further comprises a predetermined additional power gain, the open-loop gain component comprising the received signal strength indicator and the predetermined additional power gain.

35. The method of claim 32 wherein the closed-loop gain component is based a power control command received by the receiver.

36. The method of claim 32 wherein gain control of the variable gain transmitter amplifier is in decibels.

38. The method of claim 37, further comprising determining linearization data indicative of a difference between the desired gain level and an actual gain level measured using the calibrated receiver signal pathway.

39. The method of claim 37 wherein the receiver signal pathway comprises an intermediate frequency (IF) stage coupled to a demodulator stage and coupling the converted signal to the receiver signal pathway comprises coupling the converted signal to the receiver signal pathway following the IF stage.

40. The method of claim 37 wherein converting the frequency of the detected output comprises converting the frequency of the detected output to match an intermediate frequency (IF) of the receiver.

37. A method for the control of transmit power in a wireless communication device having a transmitter and a receiver, the receiver having a calibrated receiver signal pathway capable of determining the strength of a received signal, the method comprising:

setting a desired gain level of a variable gain radio frequency (RF) transmitter amplifier;

detecting an output of the variable gain transmitter amplifier indicating an actual gain level;

converting the frequency of the detected output to a frequency corresponding to an operational frequency of the receiver;

coupling the converted signal to the receiver signal pathway to permit power measurement of the signal using the calibrated receiver signal pathway.