Motor Vehicle Sensor Electrode Layout to Limit NFC Coil Interference
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Solution Overview
Problem
Existing sensor devices for motor vehicle door handles, which combine capacitive sensors and near-field transmission devices, face challenges in minimizing installation space while maintaining sensitivity, as larger sensor elements are required for optimal performance, leading to increased size and interference between the sensor electrode and near-field transmission coil.
Innovation Solution
A sensor device design where the capacitive sensor electrode is partially or completely surrounded by the near-field transmission coil, with sensor sections arranged in a non-parallel, oblique configuration to minimize mutual inductance and reduce field strength interference, allowing for a compact layout without significant disturbance to the electric field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor electrode and near-field transmission coil are arranged side by side or independently on a circuit board, then both components can be implemented, but the installation space becomes large and space-intensive
Solution Approach 1:
The sensor electrode is positioned inside the near-field transmission coil, with the coil extending over at least two, preferably three, and more preferably four sides of the sensor electrode on the substrate. This nested arrangement allows both components to share the same spatial footprint, significantly reducing the overall installation area while maintaining functional integrity of both the capacitive sensor and the inductive near-field transmission device.
2Area of stationary object
If the sensor electrode is placed within the near-field transmission coil to save space, then installation space is reduced, but the field strength of the near-field transmission coil is reduced due to mutual inductance
Solution Approach 1:
The near-field transmission coil is designed with asymmetric winding patterns and non-uniform turn densities in different regions. The coil extends over at least two, preferably three, and more preferably four sides of the sensor electrode, with varying numbers of turns and different winding configurations. This asymmetric design creates non-uniform magnetic field distribution that minimizes coupling with the sensor electrode, thereby reducing mutual inductance effects and preserving field strength while maintaining the space-saving nested arrangement.
Solution Approach 2:
Different sections of the near-field transmission coil are designed with different local characteristics, including varying turn densities, winding directions, and geometrical configurations. Regions closer to the sensor electrode have optimized winding patterns that minimize coupling, while other regions maintain strong field generation. This local optimization allows the coil to simultaneously achieve space efficiency and maintain adequate field strength for NFC communication.
3Measurement precision
If larger sensor elements are used to increase sensitivity, then detection capability is improved, but the device size and installation space requirements increase
Solution Approach 1:
The sensor electrode is positioned inside the near-field transmission coil, allowing the capacitive sensor to utilize the spatial footprint of the coil without requiring additional area. This nested configuration enables both components to share the same installation space, effectively allowing larger sensor elements to be implemented within the constrained door handle geometry without proportionally increasing the overall device size.
Solution Approach 2:
The near-field transmission coil serves dual functions: it generates the magnetic field for NFC communication and simultaneously provides a spatial framework that accommodates the capacitive sensor electrode. This multi-functionality allows the system to achieve both sensitive detection and reliable communication within a compact form factor, as the same structural elements serve multiple purposes.
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 design achieves a highly space-efficient sensor device with minimal interference between the capacitive sensor and near-field transmission components, maintaining strong field strength and simplifying user interaction by reducing visible areas for identification.
Implementation Method 1
a near-field transmission coil with at least one turn of at least one inductive near-field transmission device
Implementation Method 2
the capacitance of the sensor electrode changes. This capacitance change is detected and evaluated by the control and evaluation circuit, thus detecting an approach.
Implementation Method 3
the electric field of the near-field transmission coil couples into the sensor electrode and thereby creates a mutual inductance that counteracts the field strength of the near-field transmission coil
Data Source
Figure 1~3
AI summary
The invention relates to a sensor device (1) for a motor vehicle, comprising a substrate (2) on which a sensor electrode (3) of at least one capacitive sensor and a near-field transmission coil (4) with at least one turn of at least one inductive near-field transmission device are arranged in a planar manner, wherein the sensor electrode (3) is at least partially surrounded by the near-field transmission coil (4), wherein the sensor electrode (3) has a plurality of straight and interconnected sensor sections (5) and at least one connecting section (6), wherein the sensor sections (5) of the plurality of sensor sections (5) are subdivided into groups (7), the sensor sections (5) of which are connected in series and directly to one another, so that a first sensor section of a group transitions directly into a directly following second sensor section of the group.wherein the first sensor section and the second sensor section enclose an angle between each other, wherein each pair of groups (7) of sensor sections are connected in series by a connecting section (6) for signal purposes.