Multiband Antenna Isolation from Frame Ground
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Solution Overview
Problem
Conventional inverted F antennas mounted on portable devices suffer from reduced radiation efficiency due to capacitor coupling with the device's frame ground, leading to power loss and decreased antenna gain when the distance between the antenna and the frame ground is minimized for downsizing purposes.
Innovation Solution
A multiband antenna design featuring a conductive antenna element and ground element on an insulating film, with specific lengths and configurations to resonate at multiple frequencies, including a dielectric portion with a rectangular-parallelepiped shape and curved edges, and impedance-matching loop routes, allowing for high antenna gain without relying on the device's frame ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the antenna is mounted close to the frame ground to downsize the portable device, then the device size is reduced, but the radiation efficiency of the antenna deteriorates due to capacitor coupling
Solution Approach 1:
The invention extracts the ground function from the frame ground and creates a dedicated ground element that is electrically isolated from the frame ground. This ground element is formed on the same substrate as the antenna element, separating the antenna system from harmful interactions with the frame ground while maintaining the compact form factor.
Solution Approach 2:
The invention introduces an intermediary ground element that mediates between the antenna element and the frame ground. This ground element is connected to the antenna element through a feed line but is electrically isolated from the frame ground, serving as a buffer that prevents capacitor coupling while enabling proper antenna operation.
2Volume of moving object
If the distance between the antenna and frame ground is minimized for downsizing, then the device becomes more compact, but power loss increases due to capacitor coupling
Solution Approach 1:
The ground function is extracted from the frame ground structure and implemented as a separate ground element on the substrate. This extraction eliminates the harmful capacitor coupling path between the antenna and frame ground, reducing power loss while maintaining compact dimensions.
Solution Approach 2:
The antenna and ground element are implemented as thin conductive patterns on a flexible substrate, allowing close integration without requiring significant spacing from the frame ground. This thin-film approach enables compact design while maintaining electrical isolation through the substrate material.
3Adaptability or versatility
If the antenna is designed for multiband operation with multiple elements, then the antenna can communicate at multiple resonance frequencies, but the antenna structure becomes more complex
Solution Approach 1:
Multiple antenna elements for different frequency bands are merged onto a single substrate and share a common ground element. This combining approach achieves multiband functionality while reducing overall structural complexity compared to separate antenna assemblies for each band.
Solution Approach 2:
The ground element serves multiple functions: it provides the reference potential for the antenna element, enables multiband operation through its dimensional characteristics, and maintains electrical isolation from the frame ground. This multi-functionality reduces the need for separate components.
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
The design achieves high antenna gain and efficient radiation without using the device's frame ground, maintaining performance across multiple resonance frequency bands while allowing for compact device sizing.
Implementation Method 1
the antenna element portion includes a first antenna element having a length corresponding to a first resonance frequency, and a second antenna element having a length corresponding to a second resonance frequency; and the ground element portion includes a first side having a length to resonate at the first resonance frequency, and a second side having a length to resonate at the second resonance frequency
Implementation Method 2
a conductive antenna element and a conductive ground element which are formed on an insulating film
Implementation Method 3
when a distance between the frame ground of the portable device and the antenna is small, a phenomenon of capacitor coupling occurs between the frame ground and the antenna. The capacitor coupling denotes a capacitor component occurring between the frame ground and the antenna.
Data Source
AI summary
A multiband antenna includes a conductive antenna element portion and a conductive ground element portion which are provided on an insulating film. The antenna element portion includes a first antenna element having a length corresponding to a first resonance frequency, and a second antenna element having a length corresponding to a second resonance frequency. The ground element portion includes a first side having a length to resonate at the first resonance frequency, and a second side having a length to resonate at the second resonance frequency.