# US 8,542,768 B2 · High efficiency, remotely reconfigurable remote radio head unit system and method for wireless communications

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- Number: US 8,542,768 B2
- Document ID: US8542768B2
- Status: Granted
- Kind: B2
- Application number: 12/928,943
- Filed: 2010-12-21
- Published: 2012-06-21
- Granted: 2013-09-24
- Earliest claimed: 2009-12-21
- Assignees: Dali Systems Co. Ltd.
- Applicants: Wan Jong Kim; Kyoung Joon Cho; Shawn Patrick Stapleton; Ying Xiao
- Inventors: Wan Jong Kim; Kyoung Joon Cho; Shawn Patrick Stapleton; Ying Xiao
- Web page: https://patentgrep.com/patent/US8542768B2

## CPC

- H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)}
- H03F 1/3247: {using feedback acting on predistortion circuits (H03F1/3264 takes precedence)}
- H03F 3/24: of transmitter output stages
- 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)}
- H04B 1/0064: {with separate antennas for the more than one band (H04B1/0053 takes precedence)}
- H03F 2201/3224: Predistortion being done for compensating memory effects
- H04W 24/02: Arrangements for optimising operational condition
- H04W 84/047: {using dedicated repeater stations}
- H04W 88/08: Access point devices
- H04W 88/085: {Access point devices with remote components}
- Y02D 30/70: in wireless communication networks
- H04B: TRANSMISSION
- H03F: AMPLIFIERS
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE

## Abstract

A remote radio head unit (RRU) system for achieving high efficiency and high linearity in wideband communication systems 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. As a result, the remote radio head system is particularly suitable for wireless transmission systems, such as base-stations, repeaters, and indoor signal coverage systems.

## Claims

### Claim 1

A dual channel remote radio head unit for wireless communications comprising:
at least two power amplifiers, each receiving an input signal centered on a separate frequency and each providing as an output an amplified representation of the received input signal;
at least two feedback sensors, at least one associated with each power amplifier for providing a feedback signal that includes a representation of to the noise characteristics of the associated power amplifier;
digital logic for processing signals;
a feedback switch, controlled by the digital logic, for selecting one of the feedback signals for connection to the digital logic to enable the digital logic to generate predistortion compensation signals appropriate for each of the power amplifiers based at least in part on the feedback signals;
at least two 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 to enable the digital logic to generate predistortion compensation signals appropriate for each of the power amplifiers based at least in part on the temperature signals.

### Claim 2 (depends on 1)

The dual channel remote radio head of claim 1 further comprising digital logic implementing algorithms for ensuring that each power amplifier output is time, phase and amplitude aligned to the other power amplifier outputs.

### Claim 3 (depends on 1)

The dual channel remote radio head of claim 1 further comprising an analog to digital converter operable to convert the temperature signal to a digital signal for the digital logic.

### Claim 4 (depends on 1)

The dual channel remote radio head of claim 1 wherein the at least two power amplifiers are coupled to the digital logic using a bias control path.

### Claim 5 (depends on 1)

The dual channel remote radio head of claim 1 further comprising a duplexer coupled to the at least two power amplifiers.

### Claim 6 (depends on 1)

The dual channel remote radio head of claim 1 further comprising an optical to electrical interface coupled to the digital logic.

### Claim 7 (depends on 6)

The dual channel remote radio head of claim 6 further comprising an RF input and a baseband input coupled to the digital logic.

### Claim 8 (depends on 1)

The dual channel remote radio head of claim 1 further comprising an RF input and a baseband input coupled to the digital logic.