Antenna With Built-In Filter Impedance Matching Circuit

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Solution Overview

Problem

Conventional antennas with built-in filters face challenges in impedance matching when implemented in small electronic devices, leading to potential impedance lowering due to increased capacitance between the ground and antenna elements.

Innovation Solution

The implementation of a multiband monopole antenna with a built-in filter, featuring a matching circuit and filter circuit on a circuit board unit, which includes a low-pass filter and an n-type matching circuit to achieve impedance matching and reduce unnecessary radiation, while allowing easy detachment and replacement of antenna elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a filter is formed in a stacked dielectric structure to prevent transmission of unnecessary frequency, then the unnecessary frequency component is attenuated, but the ground and antenna element come close to each other increasing capacitance and lowering impedance

Engineering Contradiction:

Improveunnecessary frequency radiationVSAvoidimpedance matching

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

A matching circuit is introduced as an intermediary component between the antenna element and the filter circuit to compensate for the capacitance effect. The matching circuit includes inductors and capacitors configured to adjust the impedance, serving as a mediator that balances the harmful capacitance effect while maintaining the filter's frequency selection function.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The impedance parameters of the antenna system are adjusted by changing the values of inductors and capacitors in the matching circuit. By modifying these electrical parameters, the system compensates for the capacitance-induced impedance lowering while maintaining proper impedance matching for reliable operation.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If the antenna element is fixed in a compact device, then the device size is reduced, but the ground and antenna element come close to each other increasing capacitance

Engineering Contradiction:

Improveelectronic device sizeVSAvoidimpedance matching

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The matching circuit serves as an intermediary that compensates for the proximity-induced capacitance effect in compact devices. By placing this circuit between the antenna element and ground, the system can maintain proper impedance matching despite the reduced spacing required for compact form factors.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Electrical parameters of the matching circuit components are optimized to compensate for the increased capacitance resulting from compact spacing. The inductor and capacitor values are specifically chosen to counterbalance the proximity effect, enabling reliable impedance matching in small form factors.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If a filter circuit is added to the antenna system, then unnecessary frequency radiation is reduced, but the device complexity increases

Engineering Contradiction:

Improveunnecessary frequency radiationVSAvoidantenna system structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The filter circuit and matching circuit are merged into a single integrated structure that performs both frequency selection and impedance matching functions. By combining these circuits and sharing common components such as capacitors and inductors, the system reduces overall complexity while maintaining both filtering and matching capabilities.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The circuit components are designed to serve multiple functions simultaneously. The capacitors and inductors in the filter circuit also contribute to the impedance matching function, creating a multi-functional circuit that reduces the total number of components needed while achieving both frequency filtering and impedance matching.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 impedance matching and reduces unnecessary radiation without modifying the electronic device's main body, allowing for effective multiband wireless communication and easy maintenance of the antenna.

Implementation Method 1

a filter circuit (44) and a matching circuit (46) which are connected to the antenna element (31)

Methodology Applied

Scientific EffectElectromagnetic filtering: Filter (electronic)

Implementation Method 2

a matching circuit (46) which are connected to the antenna element (31)

Methodology Applied

Scientific EffectImpedance matching: Electrical Impedance Tomography

Data Source

PatentEP2434580B1Antenna with built-in filter and electronic device having the same

Publication Date: 2017.09.06 CASIO COMPUTER CO LTD

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AI summary

Disclosed is an antenna with a built-in filter, the antenna being implemented in an electronic device, comprising: an antenna element; and a circuit board unit connected to the antenna element, wherein the circuit board unit includes: a filter circuit that filters input and output signals of the antenna element; and a matching circuit that performs impedance matching of the antenna element.