TPMS Wheel Antenna Layout Using the Rim as a Waveguide
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Solution Overview
Problem
Existing TPMS antennas in vehicles face challenges with low radiation efficiency due to their small size and the damping effect of metal rims and tires, necessitating larger antennas that do not fit within the space-constrained wheel unit.
Innovation Solution
A non-resonant, electrically small antenna is positioned and oriented to excite electromagnetic modes in the wheel structure, treating it as a waveguide, enhancing radiation efficiency through simulation and capacitive loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a larger antenna is used to improve radiation efficiency, then radiation efficiency is improved, but the antenna size exceeds the space constraints of the wheel unit
Solution Approach 1:
The patent changes the operating frequency parameter to Ultra-Wide Band (UWB) range (3 GHz - 10 GHz), which has shorter wavelengths. This allows the antenna dimensions to be proportionally smaller while maintaining the electrical length requirements for efficient radiation, thus resolving the contradiction between radiation efficiency and physical size constraints
Solution Approach 2:
The patent utilizes the three-dimensional space within the wheel unit by positioning the antenna at specific locations and orientations. The antenna is placed in regions that maximize its radiation capability while fitting within the available volume, effectively using spatial dimensionality to overcome the size-efficiency trade-off
2Volume of moving object
If a smaller antenna is used to fit within the wheel unit, then the space constraint is satisfied, but radiation efficiency deteriorates
Solution Approach 1:
By transitioning to UWB frequencies with shorter wavelengths, the patent enables the use of electrically small antennas (physically small relative to wavelength) that can fit within the wheel unit while maintaining adequate radiation efficiency through proper impedance matching and positioning
Solution Approach 2:
The patent introduces capacitive loading as an intermediary element that electrically extends the effective length of the physically short antenna. This capacitive reactance compensation technique allows the small antenna to resonate at the desired UWB frequencies, improving radiation efficiency without increasing physical dimensions
3Loss of energy
If traditional resonant antennas are used, then radiation efficiency is improved, but the antenna becomes too large for the wheel unit
Solution Approach 1:
The patent changes the resonance condition by operating in the UWB frequency range where quarter-wavelength dimensions are much smaller. This parameter change allows resonant antennas to achieve efficient radiation with lengths of λ/10 or less, fitting within the wheel unit constraints
Solution Approach 2:
The patent employs adjustable and reconfigurable antenna elements that can dynamically adapt their electrical characteristics through capacitive loading and positioning adjustments. This dynamic tuning enables the antenna to achieve resonance and optimal radiation efficiency at different UWB frequencies while maintaining a compact physical size
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 achieves improved radiation efficiency across a wide frequency range, outperforming traditional quarter-wave antennas by optimizing antenna placement and electromagnetic mode excitation within the wheel structure.
Implementation Method 1
A non-resonant, electrically small antenna is positioned and oriented to excite electromagnetic modes in the wheel structure, treating it as a waveguide
Implementation Method 2
treating it as a waveguide, enhancing radiation efficiency through simulation and capacitive loading
Implementation Method 3
enhancing radiation efficiency through simulation and capacitive loading
Data Source
AI summary
A wheel unit antenna for use in a TPMS and corresponding wheel structure, in which the antenna is sized and oriented such that complete wheel structure including tire will act as a waveguide. The antenna may be non-resonant, in the form of a monopole perpendicular to a ground plane. In addition, the antenna has a length substantially shorter than a quarter wavelength, for example λ/10 or less.