Antenna Circuit Frequency Tuning for Passive Entry
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Solution Overview
Problem
Existing passive entry and immobilizer key systems require additional antenna circuits when operating at different frequency ranges for passive entry and immobilizer functions, leading to noise issues and inefficiencies.
Innovation Solution
A passive entry and immobilizer key system with three antenna circuits, where one circuit has a dual function by selectively changing its resonant frequency between very low frequency (VLF) and low frequency (LF) ranges using an inductor-capacitor combination, allowing for combined operation without the need for a fourth antenna circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fourth antenna circuit tuned to low frequency is added to support both very low frequency passive entry and low frequency immobilizer functions, then both functions can operate simultaneously, but device complexity and manufacturing cost increase
Solution Approach 1:
One antenna circuit is designed to perform dual functions by operating at different frequencies. The circuit can be tuned to very low frequency (around 20 kHz) for passive entry functionality and to low frequency (around 125 kHz or 135 kHz) for immobilizer functionality, eliminating the need for a fourth dedicated antenna circuit
Solution Approach 2:
The antenna circuit incorporates dynamic frequency tuning capability through switched capacitor networks that can change the resonant frequency of the LC circuit. This allows the same physical antenna structure to adapt its operating frequency based on the required function, transitioning between VLF and LF ranges as needed
2Reliability
If separate antenna circuits are used for very low frequency passive entry and low frequency immobilizer functions, then each function operates optimally, but manufacturing cost and device size increase
Solution Approach 1:
The patent merges the functions of separate antenna circuits into a single multi-functional antenna system. By combining the passive entry antenna and immobilizer antenna into one physical structure with frequency-tuning capability, manufacturing costs are reduced while maintaining the reliability of both functions through optimized frequency separation
3Duration of action of moving object
If battery-powered operation is implemented for extended range, then operating range increases, but energy consumption increases
Solution Approach 1:
The system uses periodic wake-up operation where the key remains in a low-power state and only activates when triggered by a vehicle signal. The battery-powered amplifier is engaged only during active communication periods, reducing overall energy consumption while maintaining extended operating range when needed
Solution Approach 2:
The key incorporates energy harvesting capability through the antenna circuit that can rectify and store electromagnetic energy from received signals in a storage capacitor. This allows the key to operate in battery-less mode for immobilizer functions by self-sufficiently harvesting energy from the vehicle's transceiver signals
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
Enables efficient operation of both passive entry and immobilizer functions using only three antenna circuits, optimizing energy use and reducing noise by automatically switching resonant frequencies based on battery voltage and received signals.
Implementation Method 1
an inductor-capacitor combination having a resonant frequency in the very low frequency range
Implementation Method 2
The transponder antenna circuit shares at least an inductive component with the antenna circuit of one of the three receiver channels
Implementation Method 3
A capacitor in the transponder antenna circuit is selectively disconnected to change the resonant frequency from a frequency in the very low frequency range to a frequency in the low frequency range
Implementation Method 4
The transponder antenna circuit includes an inductor-capacitor combination having a resonant frequency in the low frequency range. The transponder is supplied by energy received from an external transponder antenna circuit and stored in a storage capacitor
Data Source
AI summary
A passive entry and immobilizer key for vehicles comprises an integrated front-end circuit (12b) with three battery-supplied receiver channels (14, 16, 18), each connected to an associated external antenna circuit with an inductor-capacitor combination (LR, CR) having a resonant frequency in the very low frequency range. The three antennas are arranged in a three-dimensional configuration. An immobilizer transponder (22) is supplied by energy received from an external transponder antenna circuit and stored in a storage capacitor (CL). The transponder antenna circuit includes an inductor-capacitor combination (LR, CR, CL) having a resonant frequency in the low frequency range. The transponder antenna circuit shares at least one inductive component (LR) with the antenna circuit of one of the three receiver channels. A capacitor in the transponder antenna circuit is selectively disconnected to change the resonant frequency from a frequency in the very low frequency range to a frequency in the low frequency range. Accordingly, one of the three antenna circuits has a dual function. A first function is that in a three-dimensional analog front end of a passive entry system that operates in the very low frequency range. A second function is that in a transponder of an immobilizer system that operates in the much higher low frequency range. As a result, only three antenna coils need to be implemented in the key.