RFID Security Tag with Tamper-Detection Circuit

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Solution Overview

Problem

Existing RFID-based security systems for merchandise are ineffective in detecting the removal of security tags within the store premises, allowing potential thieves to exit without paying for items if the tags are surreptitiously removed before reaching the exit area.

Innovation Solution

The security tags, either in the form of hang tags or sewn-in-place tags, incorporate an RFID chip, an antenna, and a protection circuit that generates distinct signals to the RFID reader. When the tag is properly attached, it sends an 'all clear' signal; if removed, it triggers an alarm by damaging the protection circuit, which alters the signal sent to the reader, indicating tampering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If RFID readers are installed only at exit locations, then the system can detect items being taken out of the store, but it cannot detect if tags are removed within the store premises

Engineering Contradiction:

Improvetheft detection capabilityVSAvoidmonitoring system configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protection circuit is pre-configured to detect tag removal attempts before they can be completed. The circuit includes a conductive path that is disrupted when the tag is removed, triggering an alarm signal in advance before the item can be taken out of the store.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protection circuit acts as an intermediary between the RFID tag and the RFID reader. It modifies the RFID signal based on the tag's attachment status, allowing a single RFID reader at the exit to detect both legitimate items and removed tags without requiring multiple readers throughout the store.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the security tag is made removable, then it can be taken off purchased items at checkout, but thieves can remove it surreptitiously to avoid detection

Engineering Contradiction:

Improvetag removal for purchased itemsVSAvoidtheft risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The protection circuit is designed to anticipate and prevent theft by detecting the act of removal itself. When the tag is pulled away from the merchandise, the conductive path is disrupted, triggering an alarm that deters the theft before the item can be successfully stolen.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The removal action, which thieves use to their advantage, is converted into a detection trigger. The same mechanical act of pulling the tag off the item that thieves employ to avoid detection now serves to activate the alarm signal, turning the theft attempt into a detected security event.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If the protection circuit is intact, then the tag functions normally, but it sends an ambiguous signal that doesn't indicate removal

Engineering Contradiction:

Improvesignal clarityVSAvoidtag status information

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

Instead of the tag sending different signals when attached versus removed, the system inverts the approach: the intact protection circuit allows normal RFID operation, while damage to the circuit (caused by removal) creates the detectable signal change. The absence of a specific electrical path becomes the detection mechanism.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The protection circuit changes its electrical characteristics (analogous to color change) based on its integrity state. When intact, it provides a complete conductive path; when damaged by removal, the conductive path is disrupted, creating a distinguishable electrical signature that the RFID reader can detect.

Inventive Principle:

Principle #32Color changes

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 ensures that any attempt to remove the security tag within the store triggers an alarm, preventing theft by ensuring continuous monitoring and detection of the tag's presence on merchandise throughout the shopping area.

Implementation Method 1

an antenna electrically connected to the RFID chip and adapted to receive energy from an RF field

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP2777031B1Merchandise tags with removal detection for theft prevention

Publication Date: 2017.03.08 AVERY DENNISON CORP

AI summary

Security tags such as hang tags are provided for mounting on merchandise in a retail setting. The security tags include a substrate, an RFID chip, an antenna, and a protection circuit. The chip is affixed to the substrate, while the antenna and the protection circuit are electrically connected to the chip. The security tag is connected to a piece of merchandise by an attachment element associated with the substrate. The attachment element is configured such that removal of the security tag from a piece of merchandise will damage the protection circuit. The RFID chip is configured to generate a first signal which triggers an alarm if the first signal is received by an RFID reader of a security system. The RFID chip will also trigger an alarm if the protection circuit is damaged by the security tag being removed by a customer in the shopping area or other secure area.