Tightly Coupled Antenna Array for Compact MIMO Systems

Solution Overview

Problem

Current MIMO antenna arrays face challenges in achieving low correlation among antenna elements, which limits system capacity and compactness, especially in small form factor devices like mobile phones, due to the need for minimal mutual coupling, but recent studies suggest that controlled mutual coupling can enhance system capacity.

Innovation Solution

The use of Tightly Coupled Arrays or Current Sheet Antennas, which pack small antenna elements close together to create controlled mutual coupling, allowing for efficient radiation and orthogonal mode formation, thereby increasing system capacity and reducing array size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If antenna elements are spaced far apart to minimize mutual coupling, then correlation among antenna elements is reduced, but array size increases

Engineering Contradiction:

Improvelow correlation among antenna elementsVSAvoidarray size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent converts the harmful effect of mutual coupling between tightly spaced antenna elements into a beneficial orthogonal mode structure. By deliberately spacing elements closely (e.g., 0.2λ to 0.5λ) to create strong coupling, the system forms orthogonal modes through controlled coupling that actually reduces correlation and improves MIMO performance while enabling compact array design

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the spacing parameter from conventional large distances to small distances (0.2λ to 0.5λ), and introduces mode ordering based on modal significance parameter to optimize performance. This parameter transformation allows the system to achieve low correlation and high capacity in a compact form factor

Inventive Principle:

Principle #35Parameter changes

2Area of stationary object

If antenna elements are packed closely together to reduce array size, then array compactness is improved, but mutual coupling increases causing high correlation

Engineering Contradiction:

Improvearray sizeVSAvoidcorrelation among antenna elements

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent converts the harmful effect of mutual coupling between tightly spaced antenna elements into a beneficial orthogonal mode structure. By deliberately spacing elements closely (e.g., 0.2λ to 0.5λ) to create strong coupling, the system forms orthogonal modes through controlled coupling that actually reduces correlation and improves MIMO performance while enabling compact array design

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces dynamic mode ordering based on modal significance parameter that adapts to different operating conditions. The system dynamically selects and orders modes according to their significance, allowing optimal performance across varying channel conditions while maintaining compact array geometry

Inventive Principle:

Principle #15Dynamics

3Reliability

If conventional antenna spacing is used to achieve low correlation, then system reliability is improved, but device compactness deteriorates

Engineering Contradiction:

ImproveMIMO system performanceVSAvoiddevice form factor

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent converts the harmful effect of mutual coupling between tightly spaced antenna elements into a beneficial orthogonal mode structure. By deliberately spacing elements closely (e.g., 0.2λ to 0.5λ) to create strong coupling, the system forms orthogonal modes through controlled coupling that actually reduces correlation and improves MIMO performance while enabling compact array design

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent transitions from conventional spatial separation to modal domain separation. By transforming the antenna array response into orthogonal modes and ordering them by modal significance, the system achieves effective dimensionality expansion in the signal processing domain, allowing compact physical implementation with high MIMO capacity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentEP2995013B1Method and apparatus for miniaturization of MIMO systems via tightly coupled antenna array

Publication Date: 2021.03.03 SAMSUNG ELECTRONICS CO LTD

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AI summary

In a Multiple Input Multiple Output (MIMO) system, an apparatus and method includes a Tightly Coupled Array antennas (TCA) or Current Sheet Antennas (CSA). Far-field radiation patterns from any current sheet antenna are formed from the combination of the fields generated by a set of currents on the CSA of array port orthogonal modes, such as the Characteristic Modes (CM). The CM currents are generated by excitation of the CSA element ports with corresponding orthogonal voltages or currents (eigenvectors). Since the radiation patterns of the characteristic modes are orthogonal and uncorrelated, multiple signals may be propagated along the radiation patterns of the characteristic modes, each signal using a different characteristic mode or a different set of characteristic modes. Therefore, a CSA antenna utilizing array port orthogonal modes such as array port characteristic modes can support MIMO communications despite the strong mutual coupling among the antenna elements.