Antenna Array Average Power Control for RF Exposure

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Solution Overview

Problem

Existing radio equipment with advanced antenna systems (AAS) face challenges in efficiently controlling average transmitted power to comply with RF exposure regulations, particularly due to beamforming gains that concentrate radiated energy, leading to momentary power exceeding safe limits.

Innovation Solution

A control device and method for determining average total transmission power for antenna arrays, using bin-wise values of beamforming gain and total transmission power, combined with feedback control mechanisms to adjust resource usage and ensure compliance with RF exposure limits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If beamforming gain is increased to achieve high directivity, then antenna gain increases, but momentary radiated energy becomes concentrated in directional beams exceeding RF exposure limits

Engineering Contradiction:
Improveantenna gainVSAvoidRF exposure
Core Design Contradiction:
Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent applies time-averaged power control by dividing time into intervals and calculating average power over these intervals. This periodic measurement approach allows momentary high power during beamforming while ensuring the time-averaged power remains below RF exposure limits, thus resolving the contradiction between achieving high antenna gain and complying with RF exposure regulations.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent implements dynamic power adjustment by continuously monitoring and adapting the time-averaged power based on current transmission conditions. The system dynamically modifies transmission parameters to maintain compliance with RF exposure limits while optimizing beamforming performance, thereby resolving the static contradiction between fixed RF limits and dynamic beamforming requirements.

Inventive Principle:
Principle #15Dynamics

2Object-affected harmful factors

If time-averaged power is reduced to maintain RF exposure compliance, then compliance is achieved, but processing and signaling complexity increases

Engineering Contradiction:
ImproveRF exposure complianceVSAvoidprocessing complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent segments the angular coverage region into multiple bins and calculates beamforming gain separately for each bin. This segmentation allows efficient computation of time-averaged power by processing discrete angular sectors independently, thereby reducing overall processing complexity while maintaining accurate RF exposure compliance assessment.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent computes beamforming gain for specific angular bins rather than continuously across all angles. This partial computation approach reduces processing complexity by focusing calculations only on relevant angular sectors where transmission occurs, avoiding unnecessary computations while still ensuring complete RF exposure compliance.

Inventive Principle:
Principle #16Partial or excessive action

Data Source

PatentEP3864762B1Transmission power determination for an antenna array
Publication Date: 2025.07.02 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
  • EP3864762B1 patent drawingFigure 1
  • EP3864762B1 patent drawingFigure 2
  • EP3864762B1 patent drawingFigure 3

AI summary

There is provided mechanisms for determining average total transmission power for an antenna array configured for beamformed transmission within an angular coverage region. A method is performed by a control device. The method comprises determining bin-wise values of beamforming gain for a set of non-overlapping bins collectively covering the angular coverage region of the antenna array. The method comprises obtaining values of total transmission power of the beamformed transmission. The method comprises determining bin-wise values of average transmission power from the bin-wise values of beamforming gain and the values of total transmission power. The method comprises combining the bin-wise values of average transmission power into one value of average total transmission power for the antenna array.