Multi-Axis PEPS Antenna Assembly for Relay Attack Detection
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Solution Overview
Problem
Traditional passive entry/passive start (PEPS) systems are susceptible to range extender type relay station attacks, where attackers use relay devices to deceive the vehicle into thinking the key fob is closer than it actually is, leading to unauthorized access.
Innovation Solution
The implementation of a multi-axis polarized RF antenna assembly with circular and linear polarized antennas, which provides polarization diversity to accurately determine the distance and location of the key fob relative to the vehicle, preventing cross-polarization and ensuring accurate distance measurements, and includes a method to detect and counter range extender type relay station attacks by measuring time-of-flight and phase differences of RF signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PEPS systems use single-axis polarized antennas for key fob detection, then the system complexity is low, but the system is susceptible to relay station attacks and cannot accurately determine key fob distance and location
Solution Approach 1:
The antenna assembly is segmented into multiple independent antenna elements with different polarization axes (first, second, third, and fourth polarization axes). Each antenna element operates independently to detect RF signals from the key fob, allowing the system to determine both distance and angular position through comparative signal strength analysis across the segmented elements.
Solution Approach 2:
The patent extends the detection capability from a single dimension (distance only) to multiple dimensions by incorporating antennas with different polarization axes. This multi-dimensional approach enables the system to detect not only the distance to the key fob but also its angular position relative to the vehicle, thereby preventing relay station attacks that exploit single-dimensional detection limitations.
2Measurement precision
If the system uses multiple polarized antennas to accurately determine key fob location, then the security against relay attacks is improved, but the device complexity increases
Solution Approach 1:
Each antenna element in the assembly is assigned a specific polarization axis and spatial position, creating local quality variations across the system. The first and second antennas have different polarization orientations than the third and fourth antennas, allowing each element to detect signals with specific characteristics. This local differentiation enables precise determination of the key fob's angular position and distance through comparative analysis.
Solution Approach 2:
The multi-axis polarized antenna assembly serves multiple functions simultaneously: it detects the presence of the key fob, determines the distance to the key fob, determines the angular position of the key fob, and provides security against relay station attacks. This multi-functionality is achieved through a unified antenna structure that processes multiple polarization dimensions, reducing the need for separate detection systems.
3Reliability
If the PEPS system implements round trip time sniffing and multi-axis polarization detection, then relay station attacks are prevented, but the processing time and system complexity increase
Solution Approach 1:
The system performs preliminary detection using the multi-axis polarized antenna assembly to quickly assess the likelihood of a relay station attack before initiating full authentication protocols. By analyzing signal strength patterns across multiple polarization axes in advance, the system can identify suspicious conditions early and prevent unauthorized access without requiring extensive processing time for obvious attack scenarios.
Solution Approach 2:
The system implements feedback mechanisms where the results from multi-axis polarization detection and round trip time measurements continuously inform the authentication decision process. The control unit analyzes the correlation between signal strength variations across different antenna elements and the measured round trip times, using this feedback to dynamically adjust authentication requirements and detect relay station attacks in real-time without excessive processing delays.
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 solution effectively prevents unauthorized access by ensuring accurate distance and location determination of the key fob, thereby enhancing the security of the PEPS system against relay station attacks.
Implementation Method 1
A multi-axis polarized RF antenna assembly includes a circular polarized antenna, a circular isolator, and a linear polarized antenna
Implementation Method 2
measuring time-of-flight and phase differences of RF signals
Implementation Method 3
The circular isolator is connected to the conductive ring-shaped body
Data Source
AI summary
A system for includes master and sniffer devices. The master device includes: first antennas with different polarized axes; a transmitter transmitting a challenge signal via the first antennas from the vehicle to a slave device, where the slave device is a portable access device; and a receiver receiving a response signal in response to the challenge signal from the slave device. The sniffer device includes: second antennas with different polarized axes; and a receiver receiving, via the second antennas, the challenge signal from the transmitter and the response signal from the slave device. The sniffer device measures when the challenge signal and the response signal arrive at the sniffer device to provide arrival times. The master or sniffer device estimates at least one of a distance from the vehicle to the slave device or a location of the slave device relative to the vehicle based on the arrival times.