Low complexity transmitter structure for active antenna systems

• US 10,361,733 B2
• Filed: 12/13/2017
• Issued: 07/23/2019
• Est. Priority Date: 12/13/2017
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Inventors: Nammi, SaiRamesh
• Primary Examiner(s): Liu, Shuwang
• Assistant Examiner(s): McKie, Gina M
• Application Number:
  US15/841,245
• Publication Number:
  US 20190181895A1
• Time in Patent Office: 587 Days
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 17/104 of other parameters, e.g. DC offset, delay or propagation times
• CPC Class Codes: H04B 17/13 of power amplifiers, e.g. gain or non-linearity
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

Various embodiments disclosed herein provide for a low complexity transmitter structure for active antenna arrays by reducing the number of digital predistortion extraction loops that need to be performed. Digital predistortion (DPD) corrects any non-linearities in a power amplifier. By determining which power amplifiers have similar characteristics in an array, and thus may use similar predistortion coefficients, once the DPD coefficients are determine for one of the grouped power amplifiers, DPD can be performed on each of the grouped power amplifiers based on the DPD coefficients.

Claims

1. A transmitter device, comprising:

a processor; and

a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations, comprising;

identifying a first digital pre-distortion coefficient of a first power amplifier;

identifying a second digital pre-distortion coefficient of a second power amplifier, wherein the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are associated with a first power amplification nonlinearity associated with the first power amplifier and a second power amplification nonlinearity associated with the second power amplifier, respectively;

determining that the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are similar according to a similarity criterion; and

applying a first pre-distortion signal to the first power amplifier and the second power amplifier based on the first digital pre-distortion coefficient and the second digital pre-distortion coefficient.

2. The transmitter device of claim 1, wherein the operations further comprise:

sampling the first power amplifier and the second power amplifier at defined intervals to determine whether the first digital pre-distortion coefficient and the second digital pre-distortion coefficient have remained changed.

3. The transmitter device of claim 1, wherein the operations further comprise:

in response to determining that the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are no longer similar according to the similarity criterion, and in response to determining that the second digital pre-distortion coefficient is similar according to the similarity criterion of a third digital pre-distortion coefficient associated with a third power amplifier, applying a second pre-distortion signal to the second power amplifier and the third power amplifier based on the second digital pre-distortion coefficient and the third digital pre-distortion coefficient.

4. The transmitter device of claim 1, wherein the operations further comprise:

sampling the first power amplifier and the second power amplifier in response to a change in an environmental condition.

5. The transmitter device of claim 1, wherein the identifying the first digital pre-distortion coefficient and the identifying the second digital pre-distortion coefficient is based on outputs of the first power amplifier and the second power amplifier measured in response to sending a baseline signal to the first power amplifier and the second power amplifier.

6. The transmitter device of claim 1, wherein the similarity criterion is based on a difference between outputs of the first power amplifier and a second amplifier.

7. The transmitter device of claim 6, wherein the determining that the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are similar comprises determining the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are similar in response to the difference being determined to be below a threshold value.

8. The transmitter device of claim 6, wherein the operations further comprise determining that the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are no longer similar in response to the difference being determined to be above a threshold value, the first digital pre-distortion coefficient and the second digital pre-distortion coefficient.

9. The transmitter device of claim 7, wherein the operations further comprise:

measuring an adjacent channel leakage ratio associated with the first power amplifier and the second power amplifier while concurrently adjusting the threshold value; and

setting the threshold value to be a highest value of a group of values that results in the adjacent channel leakage ratio being below a predetermined value.

10. A method, comprising:

transmitting, by a transmitter device comprising a processor, a baseline signal via a group of power amplifiers associated with respective antennas of an active array antenna transmitter;

measuring, by the transmitter device, outputs of the group of power amplifiers to determine respective nonlinearities of power amplifiers of the group of power amplifiers;

determining, by the transmitter device, based on the respective nonlinearities, that a first power amplifier and a second power amplifier have a first predistortion coefficient and a second predistortion coefficient respectively that are similar according to a similarity criterion, wherein the first predistortion coefficient and the second predistortion coefficient relate to correcting a first nonlinearity associated with the first power amplifier and a second nonlinearity associated with the second power amplifier; and

based on the first predistortion coefficient, applying, by the transmitter device, a predistortion signal to the first power amplifier and the second power amplifier.

11. The method of claim 10, further comprising:

measuring, by the transmitter device, outputs of the group of power amplifiers at defined intervals to determine whether the first predistortion coefficient or the second predistortion coefficient has changed.

12. The method of claim 10, further comprising:

measuring, by the transmitter device, outputs of the group of power amplifiers in response to a change in temperature being above a predetermined temperature range.

13. The method of claim 10, wherein the similarity criterion is based on function of a difference between a first output of the first power amplifier and a second output of the second power amplifier.

14. The method of claim 13, wherein the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are determined to be similar in response to the difference being determined to be below a predetermined value, and wherein the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are determined not to be similar in response to the difference being determined to be above the predetermined value.

15. The method of claim 13, further comprising:

measuring, by the transmitter device, an adjacent channel leakage ratio associated with the first power amplifier and the second power amplifier while concurrently adjusting the predetermined value.

16. The method of claim 15, further comprising:

setting, by the transmitter device, the predetermined value to be a highest value that still results in the adjacent channel leakage ratio being below a second predetermined value.

17. A non-transitory machine-readable medium, comprising executable instructions that, when executed by a processor of a device, facilitate performance of operations, comprising:

determining a first digital pre-distortion coefficient of a first power amplifier; and

determining a second digital pre-distortion coefficient of a second power amplifier, wherein the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are associated with power amplifier nonlinearities of the first power amplifier and the second power amplifier;

determining that the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are similar according to a similarity criterion; and

applying a first pre-distortion signal to the first power amplifier and the second power amplifier as a function of the first digital pre-distortion coefficient and the second digital pre-distortion coefficient.

18. The non-transitory machine-readable medium of claim 17, wherein the similarity criterion is based on a cost function of a difference between a first output of the first power amplifier and a second output of the second power amplifier.

19. The non-transitory machine-readable medium of claim 18, wherein the determining that the first digital pre-distortion coefficient and the second digital pre-distortion coefficient are similar is in response to the difference being determined to have transitioned a threshold difference, and wherein the operations further comprise:

measuring an adjacent channel leakage ratio associated with the first power amplifier and the second power amplifier while concurrently adjusting the predetermined value threshold difference.

20. The non-transitory machine-readable medium of claim 19, wherein the operations further comprise:

setting the threshold difference to be a highest value that still results in the adjacent channel leakage ratio being below a predetermined value.