Dual-frequency antenna for HF/UHF handheld RFID reader

This paper presents a dual-frequency (HF and UHF) antenna for handheld radio frequency identification (RFID) reader to embrace the benefits offered by both the UHF and HF RFID systems. In the HF (13.56 MHz) band, a spiral-shaped loop antenna is used and placed at the outmost region of the available space. In the UHF (915 MHz) band, a quadrifilar spiral antenna (QSA) is used because it is electrically small and features a low frequency shift by platform size and is placed in the center of the HF antenna. Measurements revealed that the antenna provides a quality factor of 56.5 in the 13.56 MHz and a gain of 2.5 dBic in the 920 MHz band.