Closed-Loop Adaptive Power Control For Adjusting Bandwidth In A Mobile Handset Transmitter

• US 20110021237A1
• Filed: 02/07/2009
• Published: 01/27/2011
• Est. Priority Date: 02/08/2008
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Vasa, John E., Kahrizi, Masoud, He, Yongqiang
• Granted Patent: US 8,606,311 B2
• Time in Patent Office: Days
• US Class Current: 455/522
• CPC Class Codes: H04W 52/226 using past references to control power, e.g. look-up-table
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

A mobile handset is arranged with an adaptive power controller to controllably adjust transmit power. The adaptive power controller is coupled to a power amplifier module to form a closed feedback loop. The adaptive power control module includes a first shifter, a first sealer, an accumulator and a hold element. The first shifter and first sealer receive respective bandwidth control signals and an error signal. The first shifter and first sealer generate a modified error signal that is forwarded to and filtered by the accumulator and the hold element to generate a power control signal. The power control signal, which is generated the radio frequency subsystem of the handset can quickly and accurately track rapid changes in transmit power.

Claims

1. A method for adaptive bandwidth control in a mobile handset transmitter, comprising:

using a power detector to detect an output power level generated by a power amplifier;

generating an error signal responsive to a target power level and the output power level in a radio frequency sub-system of the mobile handset; and

applying a bandwidth control signal to the error signal to generate a modified error signal in a closed control loop of an adaptive power controller in the mobile handset, the adaptive power controller controllably forwarding one of the modified error signal or a code to generate a power control signal in response to a desired range of transmit power.

2. The method of claim 1, wherein generating the error signal responsive to the target power level comprises converting the target power level from a logarithmic scale to a linear scale.

3. The method of claim 1, wherein applying the bandwidth control signal to the error signal to generate the modified error signal comprises applying a loop bandwidth controller responsive to the target power level, the loop bandwidth controller operating in a first mode of operation or a second mode of operation in response to a transmit enable signal.

4. The method of claim 1, wherein generating the error signal responsive to the target power level and the output power level comprises generating a logarithmic value and wherein applying the first bandwidth control signal to the error signal to generate the modified error signal comprises applying a constant logarithmic value to elements within the closed control loop.

5. The method of claim 4, wherein controllably forwarding the code comprises sending a value from a look-up table in the closed control loop.

6. The method of claim 1, wherein generating the error signal responsive to the target power level comprises converting the target power level from a logarithmic scale to a linear scale.

7. The method of claim 6, wherein controllably forwarding the code to generate the power control signal comprises sending a value from a look-up table outside the closed control loop.

8. The method of claim 1, wherein controllably forwarding one of the modified error signal or the code comprises forwarding the code when the target power level is less than a desired threshold value.

9. The method of claim 1, wherein controllably forwarding one of the modified error signal or the code comprises forwarding the modified error signal when the target power level is greater than a desired threshold value.

10. The method of claim 1, further comprising:

applying an accumulator to the modified error signal to generate an integrated error signal; and

wherein applying the bandwidth control signal to the error signal comprises applying a logarithmic control path to the filtered error signal.

11. The method of claim 10, wherein the logarithmic control path comprises a slope compensator responsive to a transmit mode and a frequency band.

12. The method of claim 11, wherein the slope compensator is responsive to the target power level and a minimum power level.

13. The method of claim 1, wherein applying the bandwidth control signal to the error signal to generate the modified error signal comprises applying a loop bandwidth controller that receives the target power level in a logarithmic unit and forwards the bandwidth control signal in a linear unit.

14. The method of claim 13, wherein the loop bandwidth controller is responsive to a loop bandwidth constant.

15. The method of claim 1, further comprising:

controllably applying the power control signal to a pre-amplifier driver when communicating via EDGE and WCDMA communication standards and to a power amplifier when communicating via GMSK.

16. A mobile handset, comprising:

a power amplifier module including a power amplifier and a power detector, the power amplifier arranged to receive a transmit signal and a power control signal and generate an amplified transmit signal, the power detector configured to generate a detector output responsive to the amplified transmit signal power;

an adaptive power controller coupled to the power amplifier module, the adaptive power controller forming a closed control loop with the power amplifier module, the adaptive power controller including a first shifter, a first scaler, an accumulator and a hold element, wherein the first shifter and the first scaler are arranged to receive a bandwidth control signal and in combination generate a modified error signal responsive to an error signal generated from a target power level and the detector output, the accumulator and hold element filtering the modified error signal to generate the power control signal.

17. The handset of claim 16, further comprising a loop bandwidth controller arranged to receive the target power level and generate a first control signal and a second control signal, wherein the first control is applied to a first shifter control input and the second control signal is applied to a first scaler control input.

18. The handset of claim 17, wherein the loop bandwidth controller receives a loop bandwidth constant.

19. The handset of claim 16, wherein the first shifter and the first scaler receive a bandwidth control signal that is fixed in value.

20. The handset of claim 16, further comprising a logarithmic control path inserted in the closed loop between the accumulator and the hold element, the logarithmic control path including a log converter, a second shifter, a second scaler, the logarithmic control path responsive to a slope compensator coupled to the second shifter and the second scaler.