Antenna Feeding Network Loop for Higher Port Isolation

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Solution Overview

Problem

Achieving high isolation between antennas in multi-input multi-output (MIMO) antennas in 5G systems is challenging due to increased coupling as the number of antenna elements increases, especially for orthogonally polarized antennas, which are difficult to further isolate with fixed distances.

Innovation Solution

An improved feeding network design with a continuous conductive loop and symmetrical feeders for antennas, decoupling ports and maintaining beam pattern consistency, using a continuous conductive loop and symmetrical feeders to enhance isolation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the number of antenna elements is increased in a 5G antenna array, then the system capacity and performance are improved, but the coupling between antenna elements increases and isolation deteriorates

Engineering Contradiction:
Improvesystem capacityVSAvoidantenna coupling
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The feeding network is segmented into multiple independent feed lines, each serving specific antenna elements. This segmentation allows independent optimization of each feed line to minimize coupling between adjacent antenna elements while maintaining overall system capacity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

A specially designed feeding network structure acts as an intermediary between the signal source and antenna elements. This feeding network incorporates isolation mechanisms that mediate the electromagnetic coupling between antenna elements, reducing interference while preserving system performance.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Device complexity

If orthogonally polarized antenna elements are used with fixed distance, then the antenna array structure is simplified, but the isolation between antennas is minimized and difficult to improve

Engineering Contradiction:
Improveantenna structureVSAvoidisolation between antennas
Core Design Contradiction:
Device complexityVSObject-affected harmful factors

Solution Approach 1:

The feeding network employs asymmetric feed line configurations with different electrical lengths and impedance transformations for different antenna elements. This asymmetry creates differential signaling paths that cancel out coupling effects between orthogonally polarized elements, improving isolation without changing the physical antenna structure.

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The feeding network transforms the electromagnetic parameters (impedance, phase, amplitude) differently for each antenna element. By adjusting these parameters through carefully designed feed lines with specific electrical lengths and characteristic impedances, the coupling between orthogonally polarized elements is minimized while maintaining simple physical spacing.

Inventive Principle:
Principle #35Parameter changes

3Object-affected harmful factors

If isolation between antenna ports is increased, then the anti-interference ability is improved, but the device complexity increases

Engineering Contradiction:
Improveanti-interference abilityVSAvoidfeeding network
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

Multiple feeding functions are merged into a single integrated feeding network structure. This unified design achieves isolation between antenna ports through clever electromagnetic design rather than through multiple separate isolation components, reducing overall device complexity while maintaining high anti-interference ability.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The feeding network is designed to provide its own isolation function through intrinsic electromagnetic properties of the feed lines and their geometric arrangement. The structure serves itself to create isolation without requiring additional external isolation components or complex control mechanisms.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP4173081B1Improvement on isolation between antennas
Publication Date: 2026.03.04 NOKIA TECHNOLOGIES OY
  • EP4173081B1 patent drawingFigure 1~2
  • EP4173081B1 patent drawingFigure 3~4B
  • EP4173081B1 patent drawingFigure 5

AI summary

Embodiments of the present disclosure relate to improvement on isolation between antennas and provide an antenna, an antenna array comprising the antenna and a communication device comprising the antenna array. The antenna comprises an improved feeding network. The feeding network comprises: first and second ports each configured to transmit and/or receive a signal; first and second feed lines coupled in parallel between the first and second ports and formed into a continuous conductive loop; and first and second feeders each arranged to couple to a first node on the first feed line and to a radiating element of the antenna, and third and fourth feeders each arranged to couple to a second node on the second feed line and to the radiating element.