Vehicle Antenna Layout for Lower Parasitic Capacitance
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Solution Overview
Problem
When the distance between antennas and a ground member decreases in an antenna device, parasitic capacitance affects the antenna characteristics, leading to performance issues.
Innovation Solution
The antenna device includes a ground member attached to a vehicle reinforcement member, with substrates positioned at the ends of the ground member, featuring upright and arm portions that extend and overlap with the ground member, reducing parasitic capacitance and improving antenna characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the height of the antenna device is reduced to achieve miniaturization, then the device size is decreased, but the parasitic capacitance between the antennas and the ground member increases, degrading antenna characteristics
Solution Approach 1:
The patent positions antenna elements at the end portions of the ground member in the front-rear direction, utilizing the longitudinal dimension of the ground member to maintain antenna-ground distance while reducing overall device height. The arm portions extend in the width direction to further spatially separate antenna elements from the ground member, effectively using dimensional redistribution to mitigate parasitic capacitance during miniaturization.
Solution Approach 2:
The antenna device is segmented into multiple independent antenna elements (first antenna, second antenna, third antenna, fourth antenna) positioned at different locations on the ground member. This segmentation allows each antenna element to be independently optimized for its frequency band while maintaining adequate spacing from the ground member, reducing the overall impact of parasitic capacitance on the antenna system.
2Adaptability or versatility
If multiple antennas are accommodated in a compact antenna device, then the device integrates multiple functions, but the isolation between antennas is reduced, affecting communication performance
Solution Approach 1:
The patent utilizes three-dimensional spatial arrangement by positioning antenna elements at different locations along the ground member's length and width. The arm portions extend in the width direction while upright portions extend in the height direction, creating vertical and horizontal separation between antennas. This multi-dimensional positioning maintains isolation between antennas even when multiple antennas are integrated in a compact device.
Solution Approach 2:
Each antenna element is positioned at a specific location optimized for its frequency band characteristics. The first and second antennas are positioned at one end portion for low-frequency bands, while the third and fourth antennas are positioned at the other end portion for high-frequency bands. This localized positioning strategy ensures each antenna operates with optimal isolation and performance characteristics.
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 minimizes the impact of parasitic capacitance, enhancing the frequency band characteristics and isolation between antennas, particularly in low-frequency bands, while allowing for miniaturization and improved communication performance.
Implementation Method 1
When the distance between antennas accommodated in an antenna device and a ground member decreases in association with a reduction in the height of the antenna device, the parasitic capacitance between the antennas and the ground member may affect the characteristics of the antennas.
Data Source
AI summary
An antenna device includes: a first substrate disposed at an end portion of a ground member in one direction of a front direction and a rear direction of a vehicle, the ground member being configured to be attached to a reinforcement member of the vehicle; and a first antenna element provided at the first substrate, the first antenna element including a first upright portion formed to extend upright relative to the first substrate, and a first arm portion extending from the first upright portion, and overlapping with the end portion of the ground member in a plan view.