Vehicle Access Sensor Coil Layout for Guard Ring and RF Detection
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Solution Overview
Problem
Existing vehicle access control systems face challenges in accurately detecting user approach and recognition, particularly in improving sensitivity and compactness while minimizing parasitic magnetic fields that can impair radiofrequency signal performance.
Innovation Solution
A vehicle access control device featuring a main electrode for capacitive-type detection surrounded by a coil with a guard turn, which includes a first and second portion with notches, optimizing the guard ring function and radiofrequency transmission/reception performance, and allowing for compact design with reduced parasitic magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a radiofrequency antenna coil surrounds the main electrode to form a guard ring, then the sensitivity of capacitive detection is improved, but parasitic magnetic fields are generated that impair radiofrequency signal performance
Solution Approach 1:
The coil is divided into multiple turns, with only the first turn (guard turn) surrounding the main electrode to provide guarding function. The subsequent turns are positioned away from the electrode, reducing parasitic magnetic field generation while maintaining radiofrequency signal performance. This segmentation allows the coil to fulfill both guarding and antenna functions with reduced interference.
2Reliability
If the coil is designed with multiple turns for radiofrequency transmission, then the antenna performance is improved, but the device size increases reducing compactness
Solution Approach 1:
The coil turns are arranged in a nested configuration where multiple turns are closely coupled together. The first turn surrounds the main electrode, and subsequent turns are positioned in proximity to the first turn, creating a compact nested structure. This nesting allows multiple turns for improved radiofrequency performance while minimizing the overall device volume.
3Measurement precision
If the guard ring is brought to predetermined potential to focus electric field lines, then the detection sensitivity is improved, but the device complexity increases
Solution Approach 1:
The coil serves multiple functions: the first turn acts as a guard ring for capacitive detection by being brought to predetermined potential to focus electric field lines, while subsequent turns function as radiofrequency antenna elements. This multi-functionality reduces device complexity by eliminating the need for separate guard ring and antenna structures, as the coil performs both roles.
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
Enhances user approach detection and recognition performance with improved sensitivity and compactness, maintaining effective radiofrequency signal transmission and reception while minimizing interference from parasitic magnetic fields.
Implementation Method 1
a so-called main electrode, intended to form a capacitor with a user for carrying out a capacitive-type approach detection
Implementation Method 2
a transmitting and receiving antenna which is formed by a coil having a plurality of turns and is configured to transmit and receive a radiofrequency signal in order to identify a user
Implementation Method 3
By bringing the guard ring to a predetermined potential, for example the same potential as the main electrode, electric field lines are guided to focus on the main electrode
Data Source
AI summary
A device for a vehicle access control system, includes: a main electrode for carrying out a capacitive-type approach detection; and a transmitting and receiving antenna which is formed by a coil and is configured to transmit and receive a radiofrequency signal in order to identify a user. One turn of the coil includes: a first portion which delimits a region inside of which the main electrode is located; a second portion is offset relative to the main electrode, and at least one notch extends along one edge of the main electrode and connects the first portion and the second portion together. Each notch including two sections which are parallel to one another and connected together by a portion of the turn located at the bottom of the notch. It is thus possible to obtain a large antenna, which at the same time effectively performs a guard ring function for the main electrode.