BEAM STEERING DIGITAL PREDISTORTION

• US 20190238204A1
• Filed: 10/06/2017
• Published: 08/01/2019
• Est. Priority Date: 10/07/2016
• Status: Active Grant

• Current Assignee: NanoSemi, Incorporated (Maxlinear Incorporated)
• Original Assignee: NanoSemi, Incorporated (Maxlinear Incorporated)
• Inventors: Kim, Helen H., Megretski, Alexandre, Li, Yan, Chuang, Kevin, Mahmood, Zohaib, Huang, Yanyu
• Granted Patent: US 10,812,166 B2
• Time in Patent Office: Days
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H01Q 3/2652 Self-phasing arrays
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 2200/204 A hybrid coupler being used at the output of an amplifier circuit
• CPC Class Codes: H03F 2200/207 A hybrid coupler being used as power measuring circuit at the output of an amplifier circuit
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03F 3/68 Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04B 2001/0416 having gain or transmission power control
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/367 using predistortion

Abstract

An approach to predistortion of a first set of signals for an antenna array allows beam-steering without corrupting spectrum away from the main beam and where other users may be located. In some implementations, the predistorter uses fewer than one predistorter per signal (i.e., per power amplifier or per antenna), and/or has the computational complexity of such fewer predistorters, to generate predistortions of the first set of signals for amplification and transmission via the antenna array.

Claims

1. A method for signal predistortion comprising:

receiving a plurality of input driving signals for driving an antenna array;

converting the plurality of input driving signals to a plurality of input directional signals having fewer signals than the plurality of input driving signals, each of the plurality of input directional signals being associated with a respective direction of a plurality of directions of emission from the antenna array, wherein the plurality of directions of emission comprises a direction of a side lobe of an antenna pattern associated with the plurality of input driving signals;

processing the plurality of input directional signals to form a plurality of directional predistortion signals each of the plurality of directional predistortion signals being associated with a respective one of the plurality of input directional signals;

using the plurality of directional predistortion signals to predistort the plurality of input driving signals to yield a plurality of predistorted driving signals; and

providing the plurality of predistorted driving signals for driving the antenna array.

2. The method of claim 1, further comprising:

determining a plurality of sensed directional signals, of the same number of signals as the plurality of input directional signals; and

using at least the plurality of sensed directional signals to determine values of predistortion configuration parameters;

wherein the predistortion configuration parameters are used to process the plurality of input directional signals to form the plurality of directional predistortion signals.

3. The method of claim 2, wherein using at least the plurality of sensed directional signals to determine the values of the predistortion configuration parameters comprises performing one or more of:

optimization of the predistortion configuration parameters based on one or more objective functions computed according to at least the plurality of sensed directional signals, or selection of one or more pre-determined sets of predistortion coefficients based on a criterion computed according to the at least the plurality of sensed directional signals.

4. The method of claim 2, further comprising:

further using the plurality of input directional signals to determine the values of the predistortion configuration parameters.

5. The method of claim 1, wherein using the directional predistortion signals to predistort the input driving signals to yield the plurality of predistorted driving signals includes:

converting the directional predistortion signals to a plurality of correcting predistortion signals of the same number of signals as the input driving signals; and

combining respective ones of the plurality of input driving signals and the plurality of correcting predistortion signals to generate the plurality of predistorted driving signals.

6. The method of claim 5, wherein converting the plurality of input driving signals to the plurality of input directional signals comprises:

mapping the plurality of input driving signals to the plurality of input directional signals according to a mapping function;

and wherein converting the plurality of directional predistortion signals to the plurality of correcting predistortion signals comprises mapping the plurality of directional predistortion signals to the plurality of correcting predistortion signals according to an inverse function of the mapping function.

7. The method of claim 1, further comprising:

determining the plurality of directions of emission;

wherein converting the plurality of input driving signals to the plurality of input directional signals is performed according to the determined plurality of directions of emission.

8. The method of claim 7, wherein driving the antenna array with the plurality of predistorted driving signals is performed to emit a directional beam from the antenna array in a beam direction, wherein the plurality of directions of emissions are determined from the beam direction.

9. The method of claim 1, wherein the plurality of input directional signals (402) are representative of respective signal strengths in a plurality of desired transmission directions.

10. The method of claim 1, wherein the antenna array comprises one or more power amplifiers with respective associated non-linear behavior, and wherein using the plurality of input directional signals to form the plurality of directional predistortion signals comprises:

pre-distorting the plurality of input directional signals according to adjustable predistortion configuration parameters to generate the plurality of directional predistortion signals that, when converted to the plurality of correcting predistortion signals and combined with the plurality of input driving signals to yield and provide the plurality of predistorted driving signals cause a reduction in spectrum leakage resulting from the non-linear behavior of the power amplifiers.

22. The method of claim 1 wherein the plurality of directions of emission from the antenna array further comprises a direction of the main lobe of the antenna pattern.

23. The method of claim 22 wherein using the plurality of directional predistortion signals to predistort the plurality of input driving signals comprises reducing adjacent channel leakage in at least the direction of the side lobe.

24. The method of claim 22 wherein the plurality of directions of emission from the antenna array further comprises a direction of a spectral emission mask violation predicted from the plurality of input driving signals.

25. The method of claim 7 wherein determining the plurality of directions of emission comprises determining a direction of a main beam and one of more directions of side lobes of an antenna pattern associated with the plurality of input driving signals.

26. The method of claim 7 wherein determining the plurality of directions of emission comprises determining a direction of spectral emission mask violation.

27. The method of claim 26 wherein determining the direction of the spectral emission mask violation comprises predicting said direction from the plurality of input driving signals.

11. A beam-steering pre-distorter system comprising:

a first mapper configured to accept a plurality of input driving signals to drive an antenna array and provide a plurality of input directional signals having fewer signals than the plurality of input driving signals, each of the plurality of input directional signals being associated with a respective direction of a plurality of directions of emission from the antenna array, wherein the plurality of directions of emission comprises a direction of a side lobe of an antenna pattern associated with the plurality of input driving signals;

a pre-distorter configured to process the plurality of input directional signals to form a plurality of directional predistortion signals, each of the plurality of directional predistortion signals being associated with a respective one of the plurality of input directional signals; and

a filtering unit configured to use the plurality of directional predistortion signals to predistort the plurality of input driving signals to yield a plurality of predistorted driving signals and provide the plurality of predistorted driving signals to drive the antenna array.

12. The beam-steering pre-distorter system of claim 11, further comprising:

a beam-steering converter configured to determine a plurality of sensed directional signals, of the same number of signals as the plurality of input directional signals; and

a digital predistorter adaptation component configured to use at least the plurality of sensed directional signals to determine values of predistortion configuration parameters;

wherein the predistortion configuration parameters are used to process the plurality of input directional signals to form the plurality of directional predistortion signals.

13. The beam-steering pre-distorter system of claim 12, wherein the digital predistorter adaptation component configured to use the plurality of sensed directional signals to determine the value of the predistortion configuration parameters is configured to perform one or more of:

optimization of the predistortion configuration parameters based on one or more objective functions computed according to at least the plurality of sensed directional signals, or selection of one or more pre-determined sets of predistortion coefficients based on a criterion computed according to the at least the plurality of sensed directional signals.

14. The beam-steering pre-distorter system of claim 12, wherein the digital predistorter adaptation component is further configured to:

further use the plurality of input directional signals to determine the values of the predistortion configuration parameters.

15. The beam-steering pre-distorter system of claim 11,

wherein the filtering unit configured to use the directional predistortion signals to predistort the input driving signals to yield the plurality of predistorted driving signals comprises:

a beam-steering converter to convert the directional predistortion signals to a plurality of correcting predistortion signals of the same number of signals as the input driving signals; and

a signal combiner to combine respective ones of the plurality of input driving signals and the plurality of correcting predistortion signals to generate the plurality of predistorted driving signals.

16. The beam-steering pre-distorter system of claim 15, wherein the first mapper configured to provide the plurality of input directional signals is configured to map the plurality of input driving signals to the plurality of input directional signals according to a mapping function;

and wherein the beam-steering converter is configured to map the plurality of directional predistortion signals to the plurality of correcting predistortion signals according to an inverse function of the mapping function.

17. The beam-steering pre-distorter system of claim 11, further comprising:

a beam direction controller to determine the plurality of directions of emission;

wherein the first mapper is configured to convert the plurality of input driving signals to the plurality of input directional signals according to the determined plurality of directions of emission.

18. The beam-steering pre-distorter system of claim 11, wherein the antenna array comprises one or more power amplifiers with respective associated non-linear behavior, and wherein the pre-distorter configured to process the plurality of input directional signals to form the plurality of directional predistortion signals is configured to:

pre-distort the plurality of input directional signals according to adjustable predistortion configuration parameters to generate the plurality of directional predistortion signals that, when converted to the plurality of correcting predistortion signals, and combined with the plurality of input driving signals to provide the plurality of predistorted driving signals, cause a reduction in spectrum leakage resulting from the non-linear behavior of the power amplifiers.

19. A predistorter configured to:

receive a plurality of input driving signals for driving an antenna array;

convert the plurality of input driving signals to a plurality of input directional signals having fewer signals than the plurality of input driving signals, each of the plurality of input directional signals being associated with a respective direction of a plurality of directions of emission from the antenna array, wherein the plurality of directions of emission comprises a direction of a side lobe of an antenna pattern associated with the plurality of input driving signals;

process the plurality of input directional signals to form a plurality of directional predistortion signals, each of the plurality of directional predistortion signals being associated with a respective one of the plurality of input directional signals;

use the plurality of directional predistortion signals to predistort the plurality of input driving signals to yield a plurality of predistorted driving signals; and

provide the plurality of predistorted driving signals for driving the antenna array.

20. A design structure encoded on a non-transitory machine-readable medium, said design structure comprising elements that, when processed, generate a beam-steering pre-distorter system comprising:

a first mapper configured to accept a plurality of input driving signals to drive an antenna array and provide a plurality of input directional signals having fewer signals than the plurality of input driving signals, each of the plurality of input directional signals being associated with a respective direction of a plurality of directions of emission from the antenna array, wherein the plurality of directions of emission comprises a direction of a side lobe of an antenna pattern associated with the plurality of input driving signals;

a pre-distorter configured to process the plurality of input directional signals to form a plurality of directional predistortion signals, each of the plurality of directional predistortion signals being associated with a respective one of the plurality of input directional signals; and

a filtering unit configured to use the plurality of directional predistortion signals to predistort the plurality of input driving signals to yield a plurality of predistorted driving signals, and provide the plurality of predistorted driving signals to drive the antenna array.

21. A non-transitory computer readable media programmed with a set of computer instructions executable on a processor that, when executed, cause the operations comprising:

receiving a plurality of input driving signals for driving an antenna array;

converting the plurality of input driving signals to a plurality of input directional signals having fewer signals than the plurality of input driving signals, each of the plurality of input directional signals being associated with a respective direction of a plurality of directions of emission from the antenna array, wherein the plurality of directions of emission comprises a direction of a side lobe of an antenna pattern associated with the plurality of input driving signals;

processing the plurality of input directional signals to form a plurality of directional predistortion signals, each of the plurality of directional predistortion signals being associated with a respective one of the plurality of input directional signals;

using the plurality of directional predistortion signals to predistort the plurality of input driving signals to yield a plurality of predistorted driving signals; and

providing the plurality of predistorted driving signals for driving the antenna array.

28. A method for mitigating sidelobe emission from an antenna array comprising:

receiving a plurality of input driving signals for driving the antenna array via a plurality of non-linear signal paths, each non-linear signal path for driving a respective set of antennas of the antenna array;

determining a sidelobe direction of emission from the antenna array;

forming an input directional signal corresponding to the sidelobe direction from the plurality of input driving signals;

predistorting each of the input driving signals to form corresponding predistorted driving signals according to a processing of the input directional signal to reduce sidelobe emission in the sidelobe direction; and

providing the predistorted driving signals for driving the sets of antennas of the antenna array.