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Abdelsamad, Ziad

University of British Columbia

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 uses a radio frequency (RF) system, typically operating at 8.2 MHz, to detect shoplifted items. The shoplifting detection uses passive radio frequency resonators that are manufactured to resonate at 8.2 MHz. Current RF EAS systems suffer from inefficiency due to high power consumption and large amounts of electromagnetic interference between the transmitter and the receiver. This thesis presents a systematic approach to the development of RF EAS systems based on electromagnetic analysis techniques. The study investigated the resonant characteristics of three different RF label types. The labels are a 3cm x 3cm square label (30x30), a 4 cm x 4cm square label (die-cut), and a round label with a 4 cm diameter (circular). The analysis showed a variation in the quality factors and resonant frequencies of the labels which deviated significantly from 8.2 MHz. Two methods were then 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 to analyze the transmit and receive signal levels. Current systems also suffer from large voltage spikes caused by the hard switching action of the inductive transmitter coil. Therefore, a class E amplifier was designed to incorporate the transmitter coil in the amplifier’s load network which allows for soft switching and reduces voltage spiking. Finally, two detection methods for RF tags were investigated. The first method is based on time division duplexing with frequency hopping and the second is based on in-band full duplexing. This research project provides tools and method for analyzing inductively coupled systems in the high frequency range.

Text

2023-04-20

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/84366

Electrical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/