High efficiency, remotely reconfigurable remote radio head unit system and method for wireless communications

• US 9,948,332 B2
• Filed: 05/04/2015
• Issued: 04/17/2018
• Est. Priority Date: 12/21/2009
• Status: Active Grant

• Current Assignee: Dali Systems Co., Ltd.
• Original Assignee: Dali Systems Co., Ltd.
• Inventors: Kim, Wan-Jong, Cho, Kyoung-Joon, Stapleton, Shawn Patrick, Xiao, Ying
• Primary Examiner(s): Tran, Khanh C
• Application Number:
  US14/703,579
• Publication Number:
  US 20150381217A1
• Time in Patent Office: 1,079 Days
• Field of Search: 375285, 375295-297, 455501, 455 6713, 4551142-1143
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• 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 1/0064 with separate antennas for the more than one band H04B1/0053 takes precedence
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 84/047 using dedicated repeater stations
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: H04W 88/085 Access point devices with remote components
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A remote radio head unit (RRU) system is disclosed. The present invention is based on the method of adaptive digital predistortion to linearize a power amplifier inside the RRU. The power amplifier characteristics such as variation of linearity and asymmetric distortion of the amplifier output signal are monitored by a wideband feedback path and controlled by the adaptation algorithm in a digital module. Therefore, embodiments of the present invention can compensate for the nonlinearities as well as memory effects of the power amplifier systems and also improve performance, in terms of power added efficiency, adjacent channel leakage ratio and peak-to-average power ratio. The present disclosure enables a power amplifier system to be field reconfigurable and support multi-modulation schemes (modulation agnostic), multi-carriers, multi-frequency bands and multi-channels. Consequentially, the remote radio head system is particularly suitable for wireless transmission systems, such as base-stations, repeaters, and indoor signal coverage systems.

Claims

1. A method performed by a system including a radio frequency input path, a baseband input path, and an optical input path, the method comprising:

receiving an input signal from the radio frequency input path, the baseband input path, or the optical input path;

providing the input signal to a digital processor;

receiving, at each of a plurality of power amplifiers, the input signal from the digital processor;

amplifying, at each of the plurality of power amplifiers, the input signal to produce an output that includes an amplified representation of the received input signal;

providing a plurality of feedback paths connected to the output of each of the plurality of power amplifiers, wherein each feedback path in the plurality of feedback paths provides a feedback signal;

selecting a feedback path from the plurality of feedback paths having a feedback signal associated with a power amplifier of the plurality of power amplifiers for connection to digital processor;

determining, by the digital processor, a calibration to apply to the power amplifier based on the feedback signal; and

calibrating the power amplifier.

2. The method of claim 1, further comprising:

determining, by the digital processor, a value of a power-related variable associated with the power amplifier.

3. The method of claim 2, further comprising:

determining, by the digital processor, a predistortion to apply based on the value of the power-related variable.

4. The method of claim 1, further comprising:

applying crest factor reduction to the input signal.

5. The method of claim 1, further comprising:

providing a plurality of temperature sensors, at least one associated with each of the plurality of power amplifiers for providing a temperature signal that represents the temperature of the associated power amplifier; and

selecting one of the temperature signals for connection to the digital processor.

6. The method of claim 5, further comprising:

converting the temperature signal to a digital signal for the digital processor.

7. The method of claim 1, wherein the input signal is received from the optical input path, and wherein the input signal is provided to the digital processor via an optical to electrical interface.

8. The method of claim 1, further comprising:

selectively coupling a circulator of a plurality of circulators to the digital processor to reduce insertion loss between the plurality of power amplifiers and a duplexer coupled to the plurality of circulators.

9. The method of claim 1, wherein the feedback path is a first feedback path, wherein the feedback signal is a first feedback signal, wherein the power amplifier is a first power amplifier, and wherein the calibration is a first calibration, and wherein the method further comprises:

selecting a second feedback path from the plurality of feedback paths having a second feedback signal associated with a second power amplifier of the plurality of power amplifiers for connection to the digital processor.

10. The method of claim 9, further comprising:

determining, by the digital processor, a second calibration to apply to the second power amplifier based on the second feedback signal; and

calibrating the second power amplifier.

11. The method of claim 1, wherein the digital processor is a field programmable gate array (FPGA).

12. The method of claim 11, wherein the FPGA includes two or more digital predistortion (DPD) processors.

13. A multiple-channel remote radio head unit for wireless communications comprising:

a radio frequency input path;

a baseband input path;

an optical input path;

a digital processor configured to receive an input signal from the radio frequency input path, the baseband input path, or the optical input path;

a plurality of power amplifiers, each receiving the input signal and each providing as an output an amplified representation of the received input signal, wherein the input signal is received from the digital processor;

a plurality of feedback paths connected to an output of each of the plurality of power amplifiers, wherein each feedback path in the plurality of feedback paths provides a feedback signal;

the digital processor for processing signals, wherein the digital processor is connected to the plurality of power amplifiers; and

a feedback switch for selecting one of the feedback signals associated with a power amplifier of the plurality of power amplifiers for connection to the digital processor to calibrate the power amplifier.

14. The multiple-channel remote radio head unit of claim 13, wherein the digital processor is configured to determine a value of a power-related variable associated with the power amplifier.

15. The multiple-channel remote radio head unit of claim 14, wherein the digital processor is further configured to determine a predistortion to apply based on the value of the power-related variable.

16. The multiple-channel remote radio head unit of claim 13, wherein the digital processor is configured to apply crest factor reduction to the input signal.

17. The multiple-channel remote radio head unit of claim 13, further comprising:

a plurality of temperature sensors, at least one associated with each of the plurality of power amplifiers for providing a temperature signal that represents the temperature of the associated power amplifier; and

a temperature switch, controlled by the digital processor, for selecting one of the temperature signals for connection to the digital processor.

18. The multiple-channel remote radio head unit of claim 17, further comprising:

an analog-to-digital converter configured to convert the temperature signal to a digital signal for the digital processor.

19. The multiple-channel remote radio head unit of claim 13, wherein the input signal is received from the optical input path, and wherein the multiple-channel remote radio head unit further comprises:

an optical to electrical interface coupled to the digital processor and configured to provide the input signal to the digital processor.

20. The multiple-channel remote radio head unit of claim 13, further comprising:

a plurality of circulators, each coupled to the output of a power amplifier of the plurality of power amplifiers;

a duplexer coupled to the plurality of circulators; and

a plurality of receiver switches, each coupled to a circulator of the plurality of circulators, that selectively couples a respective circulator to the digital processor to reduce insertion loss between the plurality of power amplifiers and the duplexer.

21. The multiple-channel remote radio head unit of claim 13, wherein the radio frequency input path includes an analog downconverter, a digital upconverter, crest factor reduction, and a digital predistorter.