Thesis Defence: The Design and Implementation of an Electronic Article Surveillance System in the HF Band

Ziad Abdelsamad, supervised by Dr. Thomas Johnson, will defend their thesis titled “The Design and Implementation of an Electronic Article Surveillance System in the HF Band” in partial fulfillment of the requirements for the degree of Master of Applied Science in Electrical Engineering.

An abstract for Ziad’s thesis is included below.

Examinations are open to all members of the campus community as well as the general public.

Please email thomas.johnson@ubc.ca to receive the zoom link for this defence.

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ABSTRACT

Electronic Article Surveillance (EAS) is a well-established technology used worldwide to protect retailers against shoplifting and inventory losses. A commonly used type of EAS system uses a radio frequency (RF) system, typically operating at 8.2 MHz, to detect stolen items as they are carried through the theft detection gates of a retail store. The shoplifting detection uses passive radio frequency resonators tuned at 8.2 MHz. Despite their long history, EAS systems have seen minimal technological advancement. The currently used systems are highly inefficient and often ineffective in detecting stolen items. This thesis presents a systematic approach to the analysis and development of EAS systems, emphasizing precise measurement techniques and novel detection methods.

The resonators are attached as labels to the items on display in retail stores. A clerk deactivates the label when a customer purchases an article to avoid triggering the alarm. The RF system currently in use suffers from inefficiency due to high power consumption and a lack of robustness due to large amounts of electromagnetic interference between the transmitter and the receiver embedded inside the security gates. This study investigated the resonant characteristics of three different types of labels. The labels are with a 4 cm diameter (circular). The analysis showed a significant variation amongst the labels in terms of quality factor and resonant frequency. Following the characterization of the labels, two methods were developed to measure the strength of the magnetic coupling between the gates and the labels. The data gathered from this analysis was used to create an equivalent circuit model of the system. Subsequently, a class E amplifier is designed to drive the transmitter coil. Current systems suffer from large voltage spikes generated by the inductive transmitter coil switching on and off. The transmitter coil was used as the series inductor of the class E amplifier’s tuned load circuit to eliminate these voltage spikes. Finally, the investigation of a combination of analog and digital methods showed that cancelling the interference coupled from the transmitter to the RF spectrum of the receiver is achievable both in transient and steady-state operation. This research project provides methods based on microwave theory for analyzing and developing EAS systems. The circuit models of the developed system offer a vital tool for testing and analyzing detection algorithms for EAS systems methodically.