RFID Transponder Positioning via Multi-Antenna Time-of-Flight

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Solution Overview

Problem

RFID systems in motor vehicles are vulnerable to unauthorized activation, allowing thieves to unlock and start vehicles through signal amplification, even when the key with the RFID transponder is in a different location.

Innovation Solution

A method involving the separate emission of at least two electromagnetic alternating fields from distinct antennas to an RFID transponder, determining transit times to calculate distances and position, which can be used to reliably determine the RFID transponder's position relative to the vehicle, preventing unauthorized activation by using differentiated frequencies and cryptographically securing the signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If signal amplification or transmission system is used to extend transmission range, then unlocking or starting can occur at greater distances, but the system becomes vulnerable to unauthorized activation by thieves

Engineering Contradiction:

Improvetransmission rangeVSAvoidsecurity against unauthorized activation

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The system divides the transmission verification process into multiple independent components: multiple antennas transmit signals at different frequencies, and the transponder must respond correctly to all frequencies. This segmentation ensures that signal amplification alone is insufficient for unauthorized activation, as the thief would need to amplify multiple frequency signals simultaneously and correctly.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the frequency parameter of the transmitted signals across multiple antennas. By using different frequencies (e.g., first frequency f1, second frequency f2) and requiring the transponder to recognize and respond to all frequencies, the system prevents unauthorized activation through simple signal amplification, as the frequency discrimination cannot be easily replicated by thieves.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If multiple antennas emit electromagnetic fields at different frequencies, then position determination precision is improved, but device complexity increases

Engineering Contradiction:

Improveposition determination precisionVSAvoidnumber of antennas and frequency management

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The multiple antennas serve dual functions: they simultaneously enable position determination through time-of-flight measurements and provide security through frequency discrimination. Each antenna transmits at a different frequency, and the transponder must respond to all frequencies, making the system both precise in position determination and secure against unauthorized activation without requiring separate systems.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system merges position determination and security verification into a single integrated process. The time-of-flight measurements from multiple antennas at different frequencies are combined to determine position, while the frequency discrimination aspect simultaneously provides security. This merging reduces overall system complexity compared to having separate position determination and security systems.

Inventive Principle:

Principle #5Merging (Combining)

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 allows for precise and secure determination of the RFID transponder's position, preventing unauthorized unlocking and starting of the vehicle, enhancing security by ensuring the transponder is within a specific area for valid activation.

Implementation Method 1

separate emission of at least two electromagnetic alternating fields from at least two antenna to one RFID transponder

Methodology Applied

Scientific EffectElectromagnetic radiation: Electromagnetic Induction

Implementation Method 2

Reflection of the emitted electromagnetic alternating fields to the one RFID transponder so that the reflected electromagnetic alternating fields are sent back to the antenna

Methodology Applied

Scientific EffectElectromagnetic reflection: Reflection

Implementation Method 3

The transit times of the electromagnetic alternating fields are determined from emission to receiving back at antenna

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Data Source

PatentUS10393855B2Method of determining the position of an RFID transponder

Publication Date: 2019.08.27 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A method is disclosed for determining the position of an RFID transponder. Separate signals of at least two electromagnetic alternating fields are emitted from at least two antenna to one RFID transponder. The antenna are spaced at a distance from each other so that the two electromagnetic alternating fields are emitted at a distance from one another. The emitted electromagnetic alternating fields to the one RFID transponder are reflected so that the reflected electromagnetic alternating fields are sent back to the antenna. The transit times of the electromagnetic alternating fields are determined from emission to receiving back at the antenna. The distances between the antenna and the RFID transponder are determined, and the position of the RFID transponder from the at least two distances is determined relative to the at least two antenna.