Flat Antenna Impedance Matching for Metal Interference
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Solution Overview
Problem
Existing thin-type flat antennas, such as those made from leaky coaxial cables, face challenges in maintaining consistent communication properties when metal items are present, due to increased attenuation and complexity in designing the slot for wave leakage.
Innovation Solution
A flat antenna device with a band-like signal line path conductor and ground conductor, along with a matching circuit and radiation area setting part, is designed to maintain communication integrity even when metal items are nearby, using a signal transmission cable with a cable-side ground conductor connected to ground and a radiation area setting part to demarcate the radiation area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a leaky coaxial cable is used to create a thin-type flat antenna, then the antenna can achieve a flat plate shape, but the attenuation amount increases as the cable length increases and the slot design becomes complicated and troublesome
Solution Approach 1:
The patent extracts the radiation function from the complex leaky coaxial cable slot structure and implements it through a simpler planar antenna element with feed lines and ground conductors on a substrate, eliminating the need for complicated slot designs while maintaining the flat plate shape
Solution Approach 2:
The patent uses a planar printed circuit board structure that copies the essential functionality of the leaky coaxial cable in a simplified two-dimensional form, achieving the same radiation effect without the complexity of three-dimensional slot configurations
2Shape
If a leaky coaxial cable is used, then the antenna can be made thin and flat, but precision is demanded to the shape and position of the slot making design complicated and troublesome
Solution Approach 1:
The patent changes the structural parameters from three-dimensional slot configurations in a coaxial cable to two-dimensional planar patterns on a substrate, allowing standard PCB manufacturing tolerances to be used instead of requiring high-precision slot fabrication
Solution Approach 2:
The patent employs standard printed circuit board fabrication processes that are inexpensive and easily reproducible, replacing the need for precision-machined or carefully assembled leaky coaxial cable structures
3Shape
If a leaky coaxial cable is used in the flat antenna, then the antenna can achieve a flat shape, but when a metal item or the like is present on the periphery, the communication property is significantly varied
Solution Approach 1:
The patent introduces a ground conductor and matching circuit as intermediary elements between the feed line and the radiation element, which stabilize the impedance and reduce the influence of external metal objects on communication properties
Solution Approach 2:
The patent modifies the electrical parameters by adding impedance matching components and ground references, which normalize the antenna's electrical characteristics and make them less sensitive to variations caused by nearby metal items
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 solution provides a reliable and easy-to-design antenna configuration that minimizes variations in communication properties, even in the presence of metal items, by matching impedance and controlling radiation areas, thus ensuring consistent performance.
Implementation Method 1
a matching circuit part that matches the impedance of the antenna-side signal line path conductor to an impedance of the antenna-side first ground conductor
Implementation Method 2
a radiation area setting part that is disposed in a signal path from the signal transmission cable to the flat antenna, that demarcates the flat antenna as a radiation area, and that sets a signal path in the signal transmission cable to be a non-radiation area
Data Source
AI summary
An antenna device is provided that can be designed easily and includes a flat antenna of which communication characteristics do not change significantly even when there exist metallic objects or the like in the surroundings. Moreover, the flat antenna is provided with an antenna-side signal line path conductor, an antenna-side first ground conductor, a matching circuit part, and an antenna-side connector part which are provided in an antenna-side insulator. The antenna device further includes a signal transmission cable that is provided with a radiation area setting part in the vicinity of a cable-side connector part. The antenna device is designed such that, by connecting the antenna-side connector part and the cable-side connector part to each other, substantially the entire surface of the flat antenna serves as a radiation part that radiates electromagnetic waves.