Radio Unit Optical Interfaces for Cross-Polar Interference Cancellation

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Solution Overview

Problem

Existing point-to-point radio communication links using dual polarizations for cross-polar interference cancellation face challenges with unreliable connections and electromagnetic compatibility issues due to cable-based systems, which are difficult to install and maintain, especially in high-frequency applications.

Innovation Solution

The implementation of optical interfaces, including light emitting diodes and photo detectors, or laser emitters and detectors, for transferring cross-polar signals between radio units, aligned to facilitate rotationally symmetric optical communication, eliminating the need for external cabling and enhancing installation and maintenance efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cable-based connections are used for XPIC signal transfer between transceivers, then electromagnetic compatibility issues and installation difficulties arise, but signal transfer reliability is compromised

Engineering Contradiction:
Improveconnection reliabilityVSAvoidelectromagnetic compatibility issues
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical cable-based connection system with an optical communication system. Optical interfaces use light transmission through optical fibers or free-space optical links, eliminating the metallic cable connections that cause electromagnetic compatibility issues. This substitution maintains signal transfer reliability while removing the harmful electromagnetic interference and installation difficulties associated with cable-based systems.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If cable-based connections are used for XPIC signal transfer, then installation and maintenance become difficult especially at high locations, but connection reliability is reduced

Engineering Contradiction:
Improveinstallation easeVSAvoidconnection reliability
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The patent replaces the mechanical cable connection system with an optical interface system that eliminates the need for physical cable routing and connector assembly. Optical interfaces can be established through aligned optical ports or integrated optical paths, dramatically simplifying installation procedures especially at elevated locations where cable handling is difficult. This substitution maintains reliable signal transfer while greatly improving ease of installation and maintenance.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Loss of energy

If cable-based connections are used for high-frequency signal transfer, then signal losses increase, but connection complexity is reduced

Engineering Contradiction:
Improvesignal lossVSAvoidconnection complexity
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The patent replaces the cable-based electrical connection system with an optical communication system. Optical signals experience significantly lower attenuation at high frequencies compared to electrical signals in cables. The optical interface uses light transmission through optical fibers or free-space optical links, which have much lower signal losses at the high frequencies required for XPIC operations (bandwidths exceeding 1 GHz). Although the optical interface requires precise alignment, the overall system complexity is reduced by eliminating cable routing, connectors, and electromagnetic shielding requirements.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution provides reliable and efficient optical communication for cross-polar interference cancellation, reducing electromagnetic compatibility issues and simplifying the installation and repair of equipment by enabling alignment of radio units for optical communication without the need for expensive cabling.

Implementation Method 1

the optical transmit interface comprises a light emitting diode (LED) and the optical receive interface comprises a photo detector

Methodology Applied
Scientific EffectLight emitting diode (LED): Light Emitting Diode

Implementation Method 2

the optical transmit interface comprises a laser emitter, and the optical receive interface comprises a laser detector

Methodology Applied
Scientific EffectLaser emission: Laser

Implementation Method 3

the optical receive interface comprises a photo detector

Methodology Applied
Scientific EffectPhoto detection: Photoelectric Effect

Data Source

PatentEP3841676B1Radio unit and radio link transceiver for cross-polar signal transfer
Publication Date: 2024.03.13 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
  • EP3841676B1 patent drawingFigure 1~2
  • EP3841676B1 patent drawingFigure 3~4
  • EP3841676B1 patent drawingFigure 5

AI summary

The present disclosure relates to a radio unit (420, 420A, 420B) adapted for cross-polar signal transfer (230), comprising an optical transmit interface (430, 430A, 430B) and an optical receive interface (440, 440A, 440B) which are arranged to transfer cross-polar signals for cross-polar interference cancellation, XPIC, to and from an external source, respectively. The optical transmit interface (430, 430A, 430B) and the optical receive interface (440, 440A, 440B) are arranged at equal distances (D) from a symmetry line (450) of the interfaces, and in a plane (451) perpendicular to the symmetry line (450). Upon rotation of the radio unit (420, 420A, 420B) about the symmetry line (450) by 180 degrees, the optical transmit interface after rotation aligns with the optical receive interface before rotation, and the optical receive interface after rotation aligns with the optical transmit interface before rotation.