Capacitive Feed Antenna Isolation for Multi-Band Wireless Devices

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Solution Overview

Problem

Existing antenna configurations in wireless communication devices face interference issues between multiple frequency bands, leading to suboptimal antenna characteristics and increased size due to the need for physical separation, which compromises efficiency and band characteristics.

Innovation Solution

The design incorporates a dielectric base with a monopole type radiation electrode and a capacitive feed antenna, strategically positioned to maximize isolation and reduce feeder line loss, allowing for integration of multiple frequency bands into a smaller form factor without additional ground electrodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If two direct feed-type ungrounded mount antennae are arranged adjacently to support multiple frequency bands, then the antenna can operate in multiple frequency bands, but interference occurs between the two antennae

Engineering Contradiction:

Improvemulti-frequency band operationVSAvoidinterference between antennae

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The antenna system is segmented into two distinct types: direct feed-type ungrounded mount antenna and capacitive feed-type grounded mount antenna. Each type is optimized for specific frequency bands, reducing mutual interference while maintaining multi-band operation capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different feeding structures are applied to different antenna elements based on their operational requirements. The capacitive feed-type antenna with grounded mount structure is used for specific frequency bands where interference reduction is critical, while direct feed-type is used for other bands

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If side surface ground electrodes are provided to prevent interference between two mono antennae, then interference is reduced, but the Q value of the antenna increases which narrows the band characteristics

Engineering Contradiction:

Improveinterference between antennaeVSAvoidband characteristics

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

A ground electrode is introduced as an intermediary element between the two antenna elements. This ground electrode acts as a mediator to reduce mutual coupling and interference between antennae without requiring side surface ground electrodes that would narrow the bandwidth

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The impedance characteristics of the antenna system are modified by introducing the ground electrode and using capacitive feed structure. This changes the electrical parameters to achieve both interference reduction and maintained bandwidth characteristics

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If physical separation is increased to reduce interference between frequency bands, then interference is reduced, but the antenna size increases

Engineering Contradiction:

Improveinterference between frequency bandsVSAvoidantenna size

Core Design Contradiction:

Object-affected harmful factorsVSVolume of moving object

Solution Approach 1:

Physical mechanical separation is replaced by electromagnetic field management through capacitive coupling and grounded mount structures. This allows close physical proximity of antenna elements while maintaining electrical isolation through the capacitive feed mechanism

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 configuration ensures reduced interference, improved antenna efficiency, and compact size while maintaining satisfactory characteristics across multiple frequency bands, enhancing positional accuracy and reducing assembly costs.

Implementation Method 1

the second type radiation electrode being provided with a capacitive-coupling feeding electrode at one end of the second type radiation electrode

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS8378909B2Antenna and wireless communication apparatus

Publication Date: 2013.02.19 MURATA MFG CO LTD

AI summary

In an antenna, a first type radiation electrode and a second type radiation electrode are provided on the surface of a dielectric base, which has a predetermined external shape, or embedded in the dielectric base. The first type radiation electrode is provided with an open terminal at one end thereof and a feeding terminal at the other end thereof so as to constitute a monopole type antenna. The second type radiation electrode is provided with a capacitive-coupling feeding electrode at one end thereof and a ground connection terminal at the other end thereof so as to constitute a capacitive feed antenna. The one end of the first type radiation electrode is located opposite to the feeding electrode of the second type radiation electrode when viewed in the direction of the length of the dielectric base.