Door Handle Sensor Coil Layout for Compact NFC and Capacitive Sensing
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Solution Overview
Problem
The existing sensor devices in motor vehicle door handles face challenges in optimizing space utilization for both capacitive sensors and near-field transmission devices, leading to reduced sensitivity and efficiency due to limited installation space.
Innovation Solution
A sensor device design where the capacitive sensor electrode is formed within the inner region of the near-field transmission coil, featuring an elongate center conductor and branch conductors arranged in a specific geometry to minimize eddy currents and parasitic capacitances, allowing for a compact and sensitive integration of both components on a single or multilayer printed circuit board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the sensor electrode and near-field transmission coil are arranged on the same circuit board, then the installation space is utilized more efficiently, but the sensitivity of both components is reduced due to space constraints
Solution Approach 1:
The sensor electrode is positioned within the inner area enclosed by the near-field transmission coil winding, creating a nested arrangement where one component is placed inside the spatial envelope of the other. This allows both components to occupy the same general region on the circuit board, maximizing space utilization while maintaining their individual functional areas.
Solution Approach 2:
The sensor electrode is designed with a specific geometry featuring an elongated central conductor and multiple branch conductors that are spaced apart. This local structural optimization minimizes eddy current formation in specific areas while maintaining capacitive sensing functionality, thereby preserving sensitivity despite the compact integrated layout.
2Area of stationary object
If the sensor electrode is placed within the near-field transmission coil, then space is saved, but eddy currents are induced in the sensor electrode that generate opposing magnetic fields and limit communication capability
Solution Approach 1:
The sensor electrode is segmented into a central conductor and multiple branch conductors that are spaced apart rather than forming a continuous solid structure. This segmentation disrupts the formation of large eddy current loops, reducing the magnitude of opposing magnetic fields generated during near-field communication operations.
Solution Approach 2:
The sensor electrode employs an asymmetric design with an elongated central conductor and branch conductors extending in specific directions rather than a symmetric circular or rectangular shape. This asymmetric geometry optimizes the distribution of eddy currents and minimizes their impact on the near-field transmission coil's magnetic field while maintaining effective capacitive sensing.
3Measurement precision
If larger area is allocated to sensor electrode and transmission coil, then sensitivity is improved, but the device size increases beyond available installation space
Solution Approach 1:
The capacitive sensor electrode and near-field transmission coil are merged into a single integrated circuit board layout rather than being separate components. The sensor electrode is positioned within the coil's enclosed area, allowing both components to share the same space and benefit from mutual spatial optimization, achieving high sensitivity for both functions within a compact footprint.
Solution Approach 2:
The design utilizes the two-dimensional plane of the circuit board efficiently by arranging the sensor electrode and transmission coil in the same plane with the sensor nested within the coil's perimeter. This planar integration maximizes the use of available board area without requiring additional vertical stacking or three-dimensional space, achieving compactness while maintaining sensitivity.
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 enables reliable detection by the capacitive sensor and sensitive operation of the near-field transmission device, while reducing unwanted voltages and eddy currents, resulting in improved space utilization and performance.
Implementation Method 1
The control and evaluation circuit measures the capacitance of the electrode relative to ground. When the operator's hand approaches the electrode, the capacitance changes, and this change in capacitance is detected by the control and evaluation circuit.
Implementation Method 2
An inductive near-field transmission device is formed with a near-field transmission coil having at least one turn
Implementation Method 3
During operation of the near-field transmission device, eddy currents are induced in the free interior region of the coil within the sensor electrode. These eddy currents generate a magnetic field that opposes the generating magnetic field
Data Source
Figure 1~2
Figure 3
Figure 4a~4c
AI summary
The invention relates to a sensor device for a motor vehicle, having a printed circuit board (10; 20; 40), on which a sensor electrode (13; 22; 34) of a capacitive sensor is formed. An inductive near-field transmission device is formed with a near-field transmission coil (11; 21; 30), which has at least one turn on the printed circuit board (10; 20; 40). The near-field transmission coil (11; 21; 30) and the sensor electrode (13; 22; 34) are arranged relative to each other in such a way that the sensor electrode lies in the inner region of the near-field transmission coil surrounded by the turn, the sensor electrode having an elongate central conductor (14) and a plurality of branch conductors (15), which extend from the central conductor. The branch conductors extend out from the central conductor with spacing in such a way that the branch conductors (15) are galvanically coupled exclusively by means of the central conductor (14) and are arranged on the central conductor on opposite sides in pairs such that, for each branch conductor, an associated branch conductor is formed on the opposite side of the central conductor.