Accelerating Antenna Ramp-Down for PEPS Signal Demodulation
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Solution Overview
Problem
Conventional car entry systems using binary pulse length modulated (BPLM) signals often experience incorrectly demodulated signals due to the strength of the magnetic field varying with distance, leading to failed authentication processes in passive entry/passive start (PEPS) and immobilizer systems, especially when the transponder is close to the antenna.
Innovation Solution
An accelerating ramp-down method is introduced, where a driver signal with specific properties is asserted to synchronize with the antenna signal, allowing for a faster ramp-down of the BPLM signal, reducing the ramp-down period and ensuring the transponder voltage crosses the threshold for gap detection, even when the transponder is close to the antenna.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional BPLM signal is transmitted using standard ramp-down, then the transponder can detect the signal, but the magnetic field strength varies with distance causing incorrect demodulation and failed authentication
Solution Approach 1:
The patent applies dynamics by implementing an accelerating ramp-down sequence where the driver signal dynamically adjusts its frequency to match the antenna's resonant frequency during ramp-down. This dynamic frequency tracking ensures the magnetic field maintains proper characteristics throughout the ramp-down period, enabling accurate gap detection regardless of transponder distance from the antenna.
Solution Approach 2:
The patent changes the temporal parameters of the driver signal by implementing a multi-stage ramp-down process with accelerating frequency adjustment. The driver signal frequency is dynamically changed during the ramp-down period to follow the antenna's resonant frequency, which transforms the magnetic field decay characteristics and ensures reliable gap detection across varying distances.
2Speed
If the transponder is placed close to the antenna, then communication speed improves, but the magnetic field strength causes incorrect demodulation of BPLM signals
Solution Approach 1:
The patent uses dynamics to continuously track and follow the antenna's resonant frequency during the ramp-down period. By dynamically adjusting the driver signal frequency to match the resonant frequency at each moment, the system maintains proper magnetic field characteristics even when the transponder is in close proximity, enabling both fast and reliable authentication.
Solution Approach 2:
The patent implements feedback by using the observed resonant frequency of the antenna to control the driver signal frequency during ramp-down. The system monitors the antenna's resonant characteristics and uses this feedback to adjust the driver signal, ensuring the magnetic field maintains correct properties for accurate signal demodulation at any transponder distance.
3Measurement precision
If the ramp-down period is extended to improve gap detection, then detection accuracy improves, but the authentication process time increases
Solution Approach 1:
The patent applies the skipping principle by implementing an accelerating ramp-down that rapidly follows the resonant frequency decay. Instead of using a slow, conservative ramp-down, the system rushes through the frequency transition by dynamically tracking the resonant frequency, achieving accurate gap detection in a shorter time period.
Solution Approach 2:
The dynamic frequency tracking enables the system to achieve accurate gap detection faster by following the natural resonant decay of the antenna. This dynamic approach eliminates the need for extended ramp-down periods while maintaining detection precision, thus reducing authentication time.
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 method ensures accurate detection of the transmitted gap in BPLM signals, preventing failed authentication processes and improving the reliability of PEPS and immobilizer systems by reducing the likelihood of incorrectly demodulated signals.
Implementation Method 1
a reader (sometimes called an interrogator) in a car transmits an LF interrogation signal that supplies energy through magnetic induction to a storage capacitor in a fob
Implementation Method 2
a modulated carrier wave that during at least one operational mode exhibits a shorter ramp-down period than a resonant ramp-down of the low frequency antenna
Data Source
AI summary
Various embodiments relate to accelerating ramp-down of a modulated signal. In one embodiment, an antenna driver signal is defined and asserted to accelerate ramp-down. The accelerating ramp-down driver signal may include a series of sinusoidal-like pulses asserted at a driver output. The sinusoidal-like pulse may be synchronized by phase to a declining antenna current. Signal properties—such as phase, amplitude, delay, shape and frequency—of the sinusoidal-like pulse may be adopted to affect the ramp-down of the modulated signal.