Improving the Efficiency of Power Amplifiers in Devices Using Transmit Beamforming

• US 20030181173A1
• Filed: 03/13/2003
• Published: 09/25/2003
• Est. Priority Date: 03/21/2002
• Status: Active Grant

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: Cognio, Inc. (Cisco Systems, Inc.)
• Inventors: Luo, Sifen, Vaidyanathan, Chandra, Sugar, Gary L.
• Granted Patent: US 6,871,049 B2
• Time in Patent Office: Days
• US Class Current: 455/126
• CPC Class Codes: H01Q 3/28 varying the amplitude
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H03G 3/3089 Control of digital or coded signals
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0845 per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch rake receivers as such H04B1/7115
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Systems and methods for optimizing the efficiency of each of a plurality of power amplifiers that amplify a corresponding one of a plurality of radio frequency signals for transmission by a corresponding one of a plurality of antennas. Using transmit beamforming, the power of each amplified signal output by the power amplifiers may not be the same for all the power amplifiers, and may vary with changes in the communication channel between the transmitting device and receiving device. Each of the plurality of power amplifiers is controlled to operate with one or more operating parameters that optimize the efficiency for an output power level of corresponding ones of the radio frequency signals. By adjusting one or more operating parameters of each power amplifier according to changing requirements (e.g., the destination device and channel conditions), the efficiency of each power amplifier can be optimized. Consequently, one or more of the power amplifiers are operated with one or more operating parameters that reflects the output power actually needed for the corresponding radio frequency signal to be transmitted.

Claims

1. A method for optimizing the efficiency of each of a plurality of power amplifiers that amplify corresponding ones of a plurality of radio frequency signals for transmission by corresponding ones of a plurality of antennas, the method comprising the step of operating each of the power amplifiers with one or more operating parameters that optimize the efficiency for corresponding output power levels of corresponding radio frequency signals.

2. The method of claim 1, and further comprising a step of adjusting the one or more operational parameters for each packet to be transmitted to optimize the efficiency of each of the power amplifiers for each transmitted packet.

3. The method of claim 2, wherein the step of adjusting comprises adjusting the one or more operational parameters based on values of a plurality of transmit weights associated with the radio frequency signals to be simultaneously transmitted by the corresponding antennas to a destination device.

4. The method of claim 3, wherein the step of adjusting comprises generating a voltage or current bias for each power amplifier that optimizes the efficiency for the corresponding output power levels.

5. The method of claim 4, wherein the step of adjusting further comprises operating each of the plurality of power amplifiers with an operating voltage that optimizes the efficiency for the corresponding output power levels.

6. The method of claim 3, wherein the step of adjusting further comprises operating each of the plurality of power amplifiers with an operating voltage that optimizes the efficiency for the corresponding output power levels.

7. The method of claim 1, wherein the step of operating comprises supplying the plurality of radio frequency signals, each weighted at a power level by a corresponding transmit weight, to a plurality of self-bias boosting circuits associated with corresponding ones of the plurality of power amplifiers, wherein each self-bias boosting circuit biases the corresponding power amplifier according to the power level of the corresponding radio frequency signal supplied to it for amplification.

8. The method of claim 2, wherein the step of adjusting comprises referring to a look-up-table that indexes transmit weights to values for the one or more operational parameters.

9. The method of claim 2, wherein the step of adjusting comprises computing values for the one or more operational parameters based on the transmit weights.

10. A radio frequency signal transmission system comprising a plurality of power amplifiers that amplify corresponding ones of a plurality of radio frequency signals for transmission by corresponding ones of a plurality of antennas, each power amplifier being responsive to a corresponding control signal that adjusts at least one operational parameter to optimize the power amplifier efficiency for a corresponding output power level of the corresponding radio frequency signal.

11. The radio frequency signal transmission system of claim 10, and further comprising a processor that generates the control signals based on corresponding ones of a plurality of transmit weights associated with the plurality of radio frequency signals to be simultaneously transmitted by the corresponding antennas to a destination device.

12. The radio frequency signal transmission system of claim 10, and further comprising a plurality of power amplifier bias circuits, each associated with and connected to a corresponding one of the plurality of power amplifiers and responsive to a corresponding one of the control signals to bias the corresponding power amplifier according to the corresponding output power level for the radio frequency signal amplified by the corresponding power amplifier based on corresponding ones of a plurality of transmit weights associated with the plurality of radio frequency signals to be simultaneously transmitted by the corresponding antennas to a destination device.

13. The radio frequency signal transmission system of claim 12, and further comprising a plurality of DC/DC converters, each associated with and connected to a corresponding one of the plurality of power amplifiers and responsive to a corresponding one of the control signals to supply an operating voltage to each power amplifier according to a corresponding output power level for radio frequency signal amplified by the corresponding power amplifier.

14. The radio frequency signal transmission system of claim 10, and further comprising a plurality of DC/DC converters, each associated with and connected to a corresponding one of the plurality of power amplifiers and responsive to a corresponding one of the control signals to supply an operating voltage to each power amplifier according to a corresponding output power level for radio frequency signal amplified by the corresponding power amplifier based on corresponding ones of a plurality of transmit weights associated with the plurality of radio frequency signals to be simultaneously transmitted by the corresponding antennas to a destination device.

15. The radio frequency signal transmission system of claim 11, and further comprising a memory that stores the transmit weights.

16. The radio frequency signal transmission system of claim 15, wherein the memory stores transmit weights for each of a plurality of destination devices.

17. The radio frequency signal transmission system of claim 16, wherein the memory stores the transmit weights for the plurality of destination devices indexed against an identifier for each destination device.

18. The radio frequency signal transmission system of claim 11, wherein the processor generates the control signals by retrieving values from a look-up-table that indexes transmit weights to values of the control signals.

19. The radio frequency signal transmission system of claim 11, wherein the processor generates the control signals by computing values for the one or more operational parameters based on the transmit weights.

20. The radio frequency transmission system of claim 10, and further comprising a plurality of self-bias boosting circuits associated with corresponding ones of the plurality of power amplifiers, wherein each self-bias boosting circuit biases the corresponding power amplifier according to the power level of the corresponding radio frequency signal supplied as input to it.

21. A method for optimizing the efficiency of at least one of a plurality of power amplifiers that amplify a corresponding one of a plurality of radio frequency signals for transmission by a corresponding one of a plurality of antennas, the method comprising the step of operating the at least one power amplifier with one or more operating parameters that optimize the efficiency for an output power level to amplify a corresponding radio frequency signal.

22. A processor readable medium encoded with instructions that, when executed by a processor, cause the processor to generate power amplifier control signals based on corresponding ones of a plurality of transmit weights associated with the plurality of radio frequency signals to be simultaneously transmitted by corresponding antennas, wherein the power amplifier control signals adjust at least one operational parameter that optimizes the efficiency of a corresponding power amplifier for a corresponding output power level of the corresponding radio frequency signal.

23. The processor readable medium of claim 22, wherein the instructions encoded on the medium comprise instructions for generating a voltage or current bias for a bias circuit associated with a corresponding power amplifier based on a corresponding one of a plurality of transmit weights associated with the radio frequency signals to be simultaneously transmitted by the corresponding antennas.

24. The processor readable medium of claim 22, wherein the instructions encoded on the medium comprise instructions for generating an operating voltage for each of the-power amplifiers that optimizes the efficiency for corresponding output power levels based on a corresponding one of a plurality of transmit weights associated with the radio frequency signals to be simultaneously transmitted by the corresponding antennas.

25. A radio frequency signal transmission system comprising:

a. a plurality of power amplifiers that amplify corresponding ones of a plurality of radio frequency signals for transmission by corresponding ones of a plurality of antennas; and

b. a plurality of self-bias boosting circuits associated with corresponding ones of the plurality of power amplifiers, wherein each self-bias boosting circuit biases the corresponding power amplifier according to a power level of the corresponding radio frequency signal supplied as input to it.