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Description
Radio Frequency Identification (RFID) is a technology that has revolutionized the way contactless identification can be accomplished. Antennas for RFID, known as reader and tag, play an important role in the performance of these systems since the key features of locating and extracting information from an object rely on their appropriate design and performance; consequently, determining the whole system effectiveness. This thesis presents the investigations and design of broadband RFID reader and tag antennas that operate in the Ultra-High Frequency (UHF) band globally designated for this technology: 860 MHz to 960 MHz (11%). The reader model consists of a square microstrip patch antenna on top of an air dielectric layer while low cost FR4 material is proposed to print a 3dB quadrature branch-line coupler that, placed below the patch, serves as the feed network. The simulated model achieves broadband impedance matching w.r.t S__ ≤ -10dB from 830 MHz to 1130 MHz (30.6%) covering in excess the target UHF RFID band. Similarly, the axial ratio bandwidth w.r.t AR < 3dB ranges from 846 MHz to 1050 MHz (21.5%). The antenna exhibits good Circular Polarization throughout the band, and positive gain with a maximum value of 7.8 dBic at 920 MHz. A fabricated prototype is also presented. The tag antenna is also based on a microstrip patch which is printed on a low cost FR4 substrate. It exhibits broadband impedance matching (w.r.t. S__ < -3dB) that ranges from 860 MHz to 990 MHz (14.05%). The antenna can be mounted on metallic surfaces without considerably affecting its performance, which is a highly desirable feature when metallic objects are required to be tracked down. A simulated model and its performance is presented
