Transmit power control for multiple rate wireless communications

• US 20030114127A1
• Filed: 12/18/2001
• Published: 06/19/2003
• Est. Priority Date: 12/18/2001
• Status: Active Grant

• Current Assignee: Intellectual Ventures I LLC (Intellectual Ventures LLC)
• Original Assignee: Conexant Incorporated (Synaptics Incorporated)
• Inventors: Baldwin, Keith R.
• Granted Patent: US 6,735,420 B2
• Time in Patent Office: Days
• US Class Current: 455/245.1
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04W 52/267 taking into account the information rate
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

An RF device including a control loop for maximizing output power for each of several data rates or constellation types. The RF device includes a power detector, a power amplifier and a MAC that includes input and output adjust circuits. A power level value is generated from measured output power. The MAC compares an adjusted power level value with a set point value and generates an error value. The MAC adjusts a power control value based on the error value for controlling the gain of the power amplifier. The MAC uses a data rate signal indicative of a selected constellation type or data rate. The input adjust circuit stores one or more input adjustment values selected by the data select signal for adjusting the power level value. The output adjust circuit stores one or more output adjustment values selected by the data select signal for adjusting the power control value.

Claims

1. A power controller for a wireless transmitter that operates using a plurality of different data rates, the transmitter including a variable output power amplifier having a gain input, the power controller, comprising:

an output power detector that provides an output power level value indicative of output power;

an error circuit that compares the output power level value with a target power value and that asserts an error value indicative thereof;

a power control circuit that asserts a power control signal based on a power control value for controlling the gain input of the output power amplifier, the power control circuit regulating the power control value based on the error value;

an input normalization circuit that selectively offsets the output power level value using one or more input scale values selected by a data rate select signal indicative of data rate; and

an output normalization circuit that selectively offsets the power control value using one or more output scale values selected by the data rate select signal.

2. The power controller of claim 1, wherein the target power level is based on a first data rate.

3. The power controller of claim 2, wherein selected input and output scale values are both zero when the data rate select signal indicates the first data rate.

4. The power controller of claim 1, further comprising:

the input normalization circuit offsetting the output power level value based on a selected one of a plurality of input scale values, each corresponding to one of the plurality of data rates; and

the output normalization circuit offsetting the power control value based on a selected one of a plurality of output scale values, each corresponding to one of the plurality of data rates.

5. The power controller of claim 4, wherein the plurality of data rates are achieved using a plurality of modulation schemes including BPSK, QPSK, QAM 16 and QAM 64.

6. The power controller of claim 1, wherein the output power detector further comprises:

an average circuit that measures and averages a plurality of output power levels to generate the output power level value.

7. The power controller of claim 1, further comprising:

the input normalization circuit including a first memory that stores a plurality of input scale values and a first summing junction that combines the output power level value with one of the plurality of input scale values as selected by the data rate select signal; and

the output normalization circuit including a second memory that stores a plurality of output scale values and a second summing junction that combines the power control value with a selected one of the plurality of output scale values as selected by the data rate select signal.

8. The power controller of claim 1, wherein the power control circuit further comprises a single loop accumulator that adjusts the power control value by the error value for each data rate.

9. The power controller of claim 8, further comprising a regulator that scales the error value to control loop convergence timing.

13. The RF communication device of claim 1, wherein the plurality of different constellation types correspond to BPSK, QPSK, QAM 16 and QAM 64.

10. A radio frequency (RF) communication device that includes a power control loop for controlling output power for each of a plurality of different data rates, the RF communication device comprising:

an output portion that includes a power detector and a variable output power amplifier having a gain input;

a Baseband processor that receives a power level signal from the power detector and provides a corresponding power level value and that receives a power control value and asserts a power control signal to the gain input of the variable output power amplifier; and

a control device that receives and compares an adjusted power level value with a predetermined set point value and generates a corresponding error value and that adjusts the power control value based on the error value, the control device using a data rate signal indicative of a selected data rate, the control device including;

an input normalization adjust circuit that includes a first memory that stores one or more input adjustment values selected by the data select signal for adjusting the power level value; and

an output normalization adjust circuit that includes a second memory that stores one or more output adjustment values selected by the data select signal for adjusting the power control value.

11. The RF communication device of claim 10, the plurality of data rates achieved using a plurality of different constellation types, wherein the first and second memories store a plurality of input and output adjustment values, respectively, and wherein each corresponding pair of input and output adjustment values correspond to a selected constellation type.

12. The RF communication device of claim 11, wherein the set point value is based on a first constellation type and wherein a corresponding pair of input and output adjustment values are zero.

14. The RF communication device of claim 10, wherein the first and second memories store a plurality of input and output adjustment values, each pair of input and output adjustment values is employed to maximize output power when operating at corresponding data rates.

15. The RF communication device of claim 10, wherein the first and second memories each comprises a plurality of programmable registers.

16. The RF communication device of claim 10, wherein the variable output power amplifier comprises a variable gain amplifier having a gain input and a data output and a power amplifier having a data input, wherein the data output of the variable gain amplifier is coupled to the data input of the power amplifier.

17. The RF communication device of claim 10, wherein the control device comprises:

a first summing junction that adds a power level value with a selected input adjustment value and that provides an adjusted power level value; and

a second summing junction that compares the adjusted power level value with the set point value and that generates the error value.

18. The RF communication device of claim 17, wherein the control device includes a loop regulator that scales the error value to control convergence timing of the power control loop.

19. The RF communication device of claim 18, wherein the control device includes an accumulator that stores the power control value and a third summing junction that adjusts the power control value in the accumulator by the scaled error value.

20. The RF communication device of claim 19, wherein the control device includes a fourth summing junction that adds the adjusted power control value from the accumulator and a selected output adjustment value and that provides an adjusted power control value.

21. The RF communication device of claim 20, wherein the control device includes a third memory that stores an initial power control value that is copied into the accumulator upon power up or reset.

22. The RF communication device of claim 21, wherein the initial power control value is determined by a percentage of a measured power control value that achieves a maximum power level for a nominal data rate.

23. The RF communication device of claim 10, wherein the control device comprises a media access control (MAC) device.

24. The RF communication device of claim 10, wherein the Baseband processor includes an averaging circuit that samples the power level signal a plurality of times and that averages the samples.

25. A method of calibrating a radio frequency (RF) transmitter to maximize output power for each of a plurality of different data rates, the RF transmitter including a single power control loop that converges using a target power set point in a first memory during normal operation for each data rate, the RF transmitter further including a second memory for storing a plurality of output scale factors used to adjust a power control value and a third memory for storing a plurality of input scale factors used to adjust a power level value, the input and output scale factors selected by a data rate signal indicative of operating data rate, said method comprising:

opening the control loop during calibration;

operating the RF transmitter with the opened control loop using a selected first data rate while measuring output power metrics including a spectral leakage metric and a distortion metric;

applying and adjusting a power control value at an input of the opened control loop until a maximum desired power level is achieved for the data rate when either one of the spectral leakage metric and the distortion metric is maximized, resulting in a first power control value;

storing a power level value at an output of the opened control loop into the first memory as the target power set point; and

operating the RF transmitter with the opened control loop for each of one or more additional data rates while measuring the spectral leakage and distortion metrics, and for each additional data rate;

determining a new power control value and a new power level value when a new maximum desired power level is achieved for a corresponding data rate when either one of the spectral leakage metric and the distortion metric is maximized;

storing an output scale factor for the corresponding data rate in the second memory, the output scale factor representing a differential between the first power control value and the new power control value; and

storing an input scale factor for the corresponding data rate in the third memory, the input scale factor representing a differential between the target power set point and the new power level value.

26. The method of claim 25, the RF transmitter using a plurality of different constellation types, wherein:

said operating the RF transmitter with the opened control loop using a selected first data rate while measuring output power metrics comprises operating using a selected first constellation type;

said applying and adjusting a power control value comprising applying and adjusting the power control value until a maximum desired power level is achieved for the selected first constellation type; and

said operating the RF transmitter with the opened control loop for each of one or more additional data rates comprising operating the RF transmitter for each of one or more additional constellation types, including determining a new power control value and a new power level value for a corresponding constellation type, storing an output scale factor for the corresponding constellation type in the second memory, and storing an input scale factor for the corresponding constellation type in the third memory.

27. The method of claim 25, the RF transmitter including a fourth memory for storing an initial power control value and an accumulator used to converge the control loop during closed loop operation, the initial power control value copied to the accumulator during power up or reset, said method further comprising storing a predetermined percentage of the first power control value into the fourth memory as the initial power control value.