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

• US 9,048,797 B2
• Filed: 07/18/2014
• Issued: 06/02/2015
• 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:
  US14/335,647
• Publication Number:
  US 20150080054A1
• Time in Patent Office: 319 Days
• Field of Search: 375/285, 375295-297, 455/501, 455/67.13, 455/114.2, 455/114.3
• US Class Current: 1/1
• 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 multiple-channel remote radio head unit for wireless communications comprising:

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

a plurality of feedback paths, wherein each feedback path in the plurality of feedback paths provides a feedback signal that includes a representation of a characteristic of a power amplifier of the plurality of power amplifiers;

digital logic for processing signals;

a feedback switch for selecting one of the feedback signals for connection to the digital logic to generate predistortion compensation signals for each of the plurality of power amplifiers;

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 logic to reduce insertion loss between the plurality of power amplifiers and the duplexer.

2. The multiple-channel remote radio head unit of claim 1, wherein the plurality of power amplifiers are coupled to the digital logic using a bias control path.

3. The multiple-channel remote radio head unit of claim 1, wherein the digital logic is configured to determine, for a power amplifier of the plurality of power amplifiers, a value for a power-related variable associated with the power amplifier.

4. The multiple-channel remote radio head unit of claim 1, wherein the digital logic is further configured to determine a predistortion to apply based on a determined value.

5. The multiple-channel remote radio head unit of claim 1, further comprising an RF input and a baseband input coupled to the digital logic.

6. The multiple-channel remote radio head unit of claim 1, wherein the digital logic is configured to apply crest factor reduction to one of the input signals.

7. The multiple-channel remote radio head unit of claim 1, further comprising:

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

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

8. The multiple-channel remote radio head unit of claim 7, further comprising an analog to digital converter configured to convert the temperature signal to a digital signal for the digital logic.

9. The multiple-channel remote radio head unit of claim 1, further comprising an optical to electrical interface coupled to the digital logic.

10. A method comprising:

receiving, at each of a plurality of power amplifiers, an input signal;

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

providing a plurality of feedback paths, wherein each feedback path in the plurality of feedback paths provides a feedback signal that includes a representation of a characteristic of a power amplifier of the plurality of power amplifiers;

selecting one of the feedback signals for connection to digital logic to generate predistortion compensation signals for each of the plurality of power amplifiers; and

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

11. The method of claim 10, wherein the plurality of power amplifiers are coupled to the digital logic using a bias control path.

12. The method of claim 10, further comprising:

determining, by the digital logic and for a power amplifier of the plurality of power amplifiers, a value of a power-related variable associated with the power amplifier.

13. The method of claim 12, further comprising:

determining, by the digital logic, a predistortion to apply based on a determined value.

14. The method of claim 10, further comprising:

receiving an RF input and a baseband input at the digital logic.

15. The method of claim 10, further comprising:

applying crest factor reduction to one of the input signals.

16. The method of claim 10, further comprising:

providing a plurality of temperature sensors, at least one associated with each power amplifier 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 logic.

17. The method of claim 16, further comprising:

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

18. The method of claim 10, further comprising:

receiving, at an optical to electrical interface, an optical signal input to the digital logic.