In this paper, a miniature antenna for a passive UHF RFID tag is designed, which may be built in a portable device. Matching techniques for a Gen2 tag IC are employed to enhance the readable distance of the tag for long-range reading purposes, where quasi-lumped and lumped elements are used to match the chip antenna to the tag IC having complex input impedance. A commercial simulator, HFSS? is used to analyze the performance of the antenna. Also, measurements in an anechoic chamber of the RFID education and research center at National Taiwan University of Science and Technology are performed to evaluate the readable range of the chip tag, which is more than 5 m for a reader with an EIRP equal to 4W. The chip antenna operating in the 900 MHz RFID band proposed here has dimensions of only 10× 9.5 × 0.8 mm~3. Thus, this miniature tag may be flexibly built in a portable device to allow long-range reading.
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