Vehicle Key 3D Coil Signal Strength Selection
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Solution Overview
Problem
Existing radio keys with 3D coil arrangements for passive entry systems face reliability issues due to inefficient coil selection processes, which affect performance and accuracy in low-frequency signal reception.
Innovation Solution
The central control circuit, equipped with a microcontroller, wakes up after receiving a wake-up signal and then evaluates signals from each coil in the 3D coil arrangement to select the optimal coil for low-frequency signal reception based on signal strength (RSSI) or response times, rather than relying on preselection by the receiving circuit, ensuring improved reliability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the receiving circuit preselects a coil before the central control circuit is activated, then the system can quickly respond to wake-up signals, but the reliability of low-frequency signal reception deteriorates due to inadequate coil evaluation
Solution Approach 1:
The receiving circuit performs preliminary wake-up signal detection and preselects a candidate coil before the central control circuit is fully activated. This preliminary action enables quick response to wake-up calls while the subsequent full evaluation by the activated central control circuit ensures reliable signal reception.
Solution Approach 2:
The receiving circuit acts as an intermediary between the wake-up signal and the central control circuit. It performs initial coil selection and signal evaluation, then transfers control to the central control circuit for final decision-making, ensuring both rapid response and high reliability.
2Reliability
If the central control circuit evaluates all coils after wake-up, then the reliability of coil selection is improved, but the energy consumption increases due to additional processing
Solution Approach 1:
The receiving circuit performs a partial evaluation of coils before the central control circuit is activated, identifying candidate coils that meet basic criteria. The central control circuit then performs a more thorough evaluation only on these candidates, rather than all coils, achieving high reliability with reduced energy consumption.
Solution Approach 2:
The receiving circuit performs preliminary coil evaluation and filtering before the energy-intensive central control circuit is fully activated. This preliminary action reduces the number of coils that require full evaluation, thereby reducing overall energy consumption while maintaining selection reliability.
3Device complexity
If the receiving circuit makes the coil selection, then the system operation is simplified, but the measurement precision of signal strength evaluation deteriorates
Solution Approach 1:
The coil selection process is segmented into two stages: initial filtering by the receiving circuit based on basic criteria, and precise signal strength measurement by the central control circuit. This segmentation allows the system to maintain simplicity in the first stage while achieving high measurement precision in the second stage.
Solution Approach 2:
The receiving circuit serves as an intermediary that performs initial coil filtering based on simple criteria, then transfers control to the central control circuit for precise signal strength measurement. This intermediary approach maintains system simplicity while enabling high-precision evaluation when needed.
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 approach significantly enhances the reliability of low-frequency signal reception and decoding, reducing unnecessary energy consumption and improving system performance by allowing software-based coil selection post-wake-up, making it suitable for retrofitting existing systems.
Implementation Method 1
a coil arrangement which is designed as a so-called 3D coil arrangement for signal reception in the low-frequency (LF) frequency range
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a wireless key (2) for an access system of a motor vehicle, comprising a receiver circuit (10) with at least three LF receiver coils for a low-frequency signal reception. The LF receiver coils are oriented in different spatial directions. A control circuit (11) with a microcontroller is coupled to the receiver circuit (10), and the control circuit with the microcontroller can assume different operating states, at least one operating state of which is an energy-reduced idle state and one operating state is an active operating state. The receiver circuit (10) can wake up the control circuit (11) out of the energy-reduced idle state when a signal is received via the LF receiver coils. The central control circuit (11) actuates each of the LF receiver coils separately after waking up from the idle state and requests a received signal strength. On the basis of the signal strengths, the control circuit selects the LF receiver coil with the highest signal strength for a subsequent signal reception.