A circularly polarized passive RFID tag on wall

This paper presents the design, measurement and results of a square-shaped microstrip antenna on wall for a passive RFID tag compliant to EPC Global Class 1-Gen2. The tag antenna operates at the European Ultra-High Frequency (UHF) band and is excited by a dual inset feed network to achieve Circular Polarization (CP). The antenna size is reduced as well as the CP bandwidth is extended by inserting a cross slot at the center of the square patch. The proposed tag is characterized in an anechoic chamber and is tested in the laboratory hallway using a commercial UHF RFID reader. In comparing our proposed tag to commercial RFID tags, the read-range of our tag is improved in both cases: tag in free space and tag on wall.