Apparatus and method for accurate and efficient transmit power control

• US 20110105061A1
• Filed: 10/30/2009
• Published: 05/05/2011
• Est. Priority Date: 10/30/2009
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Ng, Horace, Yu, Huili
• Granted Patent: US 8,233,859 B2
• Time in Patent Office: Days
• US Class Current: 455/127.2
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

Abstract

A technique to provide accurate and efficient transmit power control by providing offset values to modify a base input gain value for a gain control circuit used to set a transmit power gain in a mobile phone. The modified gain value compensates for a ripple offset and power level offset caused by a difference in operating temperature and operating frequency from values obtained during calibration at a calibration frequency and temperature.

Claims

1. A method comprising:

determining base input gain values for a plurality of transmit power levels for a gain control circuit at a selected transmit frequency and at a selected temperature, in which the base input gain values compensate for power gains and losses in transmitter stages utilized for transmitting a signal;

storing the base input gain values and respective power levels;

identifying a variation in a level of the transmit power level at frequencies other than the selected transmit frequency as a ripple across a frequency band;

determining a ripple offset value at each of a plurality of frequencies across the frequency band to substantially smooth the ripple;

storing the ripple offset values;

identifying a shift in the ripple across the frequency band at temperatures other than the selected temperature of operation;

determining a correlation between the ripple shift and a change in temperature;

storing the correlation between the ripple shift and the change in temperature;

identifying a difference in the transmit power levels at temperatures other than the selected temperature;

determining a correlation of the transmit power level between the other temperatures and the selected temperature;

storing the correlation of the transmit power level between the other temperatures and the selected temperature; and

providing a routine to run on a processor to select one of the base input gain values corresponding to an expected transmit power output for transmitting the signal, modifying the base input gain value by offsets provided by a ripple offset value and the two correlations corresponding to frequency and temperature of operation.

2. The method of claim 1, wherein providing the routine includes providing the routine to process a received transmit power control instruction to determine the expected transmit power output for transmitting the signal.

3. The method of claim 2, wherein providing the routine to process the received transmit power control instruction further includes the routine to filter a sequence of at least two consecutive transmit power control instructions and to respond to a first of the transmit power control instructions only when the at least two consecutive transmit power control instructions do not toggle to command a transmit power increase and a transmit power decrease.

4. The method of claim 1, wherein providing the routine includes providing the routine to run on a mobile telephone.

5. The method of claim 4, wherein providing the routine includes providing the routine to run on a baseband processor of the mobile telephone.

6. The method of claim 5, wherein providing the routine includes for the routine to provide the modified input gain value as an input value to a digital-to-analog converter (DAC) that operates as the gain control circuit, in which an output from the DAC is used as a gain control signal to set a power level for transmitting the signal.

7. The method of claim 1, wherein determining the base input gain value and determining the offset value at each of the plurality of frequencies is performed for each gain mode when multiple gain modes are present for transmitting the signal.

8. A method comprising:

identifying an expected transmit power output at an antenna to transmit a signal;

selecting a base input gain value for a gain control circuit corresponding to the expected power output from a plurality of transmit power level base input gain values, wherein the base input gain values compensate for power gains and losses in transmitter stages utilized for transmitting the signal;

determining a frequency of operation to transmit the signal;

determining a temperature of operation;

selecting a ripple offset value corresponding to the frequency and temperature of operation, in which the ripple offset value corrects for a variation in a level of the transmit power between the frequency of operation and a calibration frequency used to set the plurality of base input gain values and also corrects for a ripple shift between the temperature of operation and a calibration temperature used to set the plurality of base input gain values;

selecting a power level offset value corresponding to the temperature of operation to correct for power level difference between the temperature of operation and the calibration temperature;

combining the selected ripple offset value and the selected power level offset value with the selected base input gain value to derive a modified input gain value; and

applying the modified gain value to set a gain of one of the transmitter stages to transmit the signal.

9. The method of claim 8, further comprising receiving a power control instruction to determine the expected transmit power output for transmitting the signal.

10. The method of claim 9, wherein identifying the expected transmit power control includes filtering a sequence of at least two consecutive transmit power control instructions and to respond to a first of the transmit power control instructions only when the at least two consecutive transmit power control instructions do not toggle to command a transmit power increase and a transmit power decrease.

11. The method of claim 8, wherein combining the selected ripple offset value and the selected power level offset value with the selected base input gain value includes running a routine in a baseband processor of a mobile phone to derive the modified gain value.

12. The method of claim 11, wherein applying the modified gain value includes applying the modified gain value as an input value to a digital-to-analog converter (DAC), in which an output from the DAC is used as a gain control signal to set a gain of an amplifier.

13. The method of claim 8, further comprising selecting a gain mode prior to selecting the base input gain value and selecting the ripple offset value when multiple gain modes are present for transmitting the signal.

14. An apparatus comprising:

a baseband processor to identify an expected transmit power output at an antenna to transmit a signal, select a base input gain value corresponding to the expected power output from a plurality of transmit power level base input gain values, wherein the base input gain values compensate for power gains and losses in transmitter stages utilized for transmitting the signal, the baseband processor to also determine a frequency of operation to transmit the signal and a temperature of operation to select a ripple offset value corresponding to the frequency and temperature of operation, in which the ripple offset value corrects for a variation in a level of the transmit power between the frequency of operation and a calibration frequency used to set the plurality of base input gain values and also corrects for a ripple shift between the temperature of operation and a calibration temperature used to set the plurality of base input gain values, the baseband processor to also select a power level offset value corresponding to the temperature of operation to correct for power level difference between at the temperature of operation and the calibration temperature, wherein the baseband processor combines the selected ripple offset value and the selected power level offset value with the selected base input gain value to derive a modified input gain value;

a gain control circuit coupled to the baseband processor to receive the modified gain value for setting a transmitter gain; and

a gain stage coupled to receive the modified gain value to set the transmitter gain.

15. The apparatus of claim 14, further comprising a receiver to receive a transmit power control instruction and the baseband processor to determine the expected transmit power output for transmitting the signal based on the received transmit power control instruction.

16. The apparatus of claim 15, wherein the baseband processor includes a filtering routine to process a sequence of at least two consecutive transmit power control instructions and to respond to a first of the transmit power control instructions only when the at least two consecutive transmit power control instructions do not toggle to command a transmit power increase and a transmit power decrease.

17. The apparatus of claim 14, wherein the gain control circuit is a digital-to-analog converter (DAC), in which an output from the DAC is used as a gain control signal for setting the transmitter gain.

18. The method of claim 17, wherein the gain stage is an amplifier for setting the transmitter gain of a mobile phone.