Method and apparatus for controlling a supply voltage to a power amplifier

• US 7,634,240 B2
• Filed: 01/31/2006
• Issued: 12/15/2009
• Est. Priority Date: 01/31/2006
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Mathes, Patrick C., Hagen, Rodney, Mitzlaff, James E.
• Primary Examiner(s): Le; Nhan T
• Application Number:
  US11/345,006
• Publication Number:
  US 20070178856A1
• Time in Patent Office: 1,414 Days
• Field of Search: 455/115.1, 455/115.2, 455/115.3, 455/115.4, 455/127.1, 455/127.3, 455/127.5
• US Class Current: 455/127.3
• CPC Class Codes: H03F 1/02 Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 1/3294 Acting on the real and imaginary components of the input signal
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 2001/045 with means for improving efficiency

Abstract

A supply voltage to a power amplifier is controlled. A signal at a single point in a power amplifier is detected. A signal parameter is determined for the detected signal. The signal parameter is compared to at least one predetermined limit. This comparison result is used to determine whether to adjust a supply voltage to the power amplifier. The signal parameter is, for example, an average power or a peak-to-average power ratio.

Claims

1. A method for controlling a supply voltage to a power amplifier comprising the steps of:

detecting a signal at a single point in an input path of a power amplifier to produce a detected signal;

determining a peak-to-average power ratio based on the detected signal;

comparing the peak-to-average power ratio to a first predetermined peak-to-average power ratio value and a second predetermined peak-to-average power ratio value that is lower than the first predetermined peak-to-average power ratio value to generate a comparison result that indicates a level of compression in the power amplifier;

increasing the supply voltage when the peak-to-average power ratio is above the first predetermined peak-to-average power ratio value; and

reducing the supply voltage when the peak-to-average power ratio is below the second predetermined peak-to-average power ratio value.

2. The method of claim 1 wherein the peak-to-average power ratio is determined by:

determining an average power for the signal;

determining a largest power value for the signal; and

dividing the largest power value by the average power.

3. The method of claim 1, wherein the supply voltage comprises one of:

a constant voltage; and

a voltage generated by a power supply modulator.

4. The method of claim 1 wherein the signal is a plurality of digitized samples received from a beginning measurement point to an end measurement point;

and

the step of determining the peak-to-average power ratio includes the steps of;

determining a power for each digitized sample of the plurality of digitized samples;

determining a total number of digitized samples from the beginning measurement point to the end measurement point;

summing the power for each digitized sample of the plurality of digitized samples to produce a total power;

determining a largest power value for a digitized sample of the plurality of digitized samples;

determining an average power by dividing the total power by the total number of digitized samples;

determining the peak-to-average power ratio by dividing the largest power value by the average power.

5. The method of claim 1 wherein if the peak-to-average power ratio is within the first predetermined peak-to-average power ratio value and the second predetermined peak-to-average power ratio value, then leaving the supply voltage at a current value.

6. The method of claim 1 wherein the power amplifier is one of a Cartesian linear power amplifier or a predistortion linear power amplifier.

7. An apparatus for controlling a supply voltage to a power amplifier comprising:

a power amplifier; and

a processor coupled to the power amplifier that;

detects a signal at a single point in an input path of the power amplifier to produce a detected signal;

determines a peak-to-average power ratio based on the detected signal;

compares the peak-to-average power ratio to a first predetermined peak-to-average power ratio value and a second predetermined peak-to-average power ratio value that is lower than the first predetermined peak-to-average power ratio value to generate a comparison result that indicates a level of compression in the power amplifier;

causes an increase in the supply voltage when the peak-to-average power ratio is above the first predetermined peak-to-average power ratio value; and

causes a reduction in the supply voltage when the peak-to-average power ratio is below the second predetermined peak-to-average power ratio value.

8. The apparatus of claim 7 wherein the peak-to-average power ratio is determined by:

determining an average power for the signal;

determining a largest power value for the signal; and

dividing the largest power value by the average power.

9. The apparatus of claim 7 wherein the signal is a plurality of digitized samples received from a beginning measurement point to an end measurement point;

and

the peak-to-average power ratio is determined by the processor;

determining a power for each digitized sample of the plurality of digitized samples;

determining a total number of digitized samples from the beginning measurement point to the end measurement point;

summing the power for each digitized sample of the plurality of digitized samples to produce a total power;

determining a largest power value for a digitized sample of the plurality of digitized samples;

determining an average power by dividing the total power by the total number of digitized samples;

determining the peak-to-average power ratio by dividing the largest power value by the average power.

10. A method for controlling a supply voltage to a power amplifier comprising the steps of:

detecting a signal at a single point in a power amplifier to produce a detected signal;

determining an average power level based on the detected signal;

comparing the average power level to a first predetermined average power value and a second predetermined average power value that is lower than the first predetermined average power value to generate a comparison result that indicates a level of compression in the power amplifier;

increasing the supply voltage when the average power level is above the first predetermined average power value; and

reducing the supply voltage when the average power level is below the second predetermined average power value.

11. The method of claim 10, wherein detecting the signal at the single point in the power amplifier comprises detecting the signal at an input path of an error amplifier in a feed forward amplifier.

12. The method of claim 10, wherein detecting the signal at the single point in the power amplifier comprises detecting the signal at an output path of an error amplifier in a feed forward amplifier.