A Small and Lightweight Antenna for Handheld RFID Reader Applications

This letter presents a circularly polarized antenna suitable for handheld radio frequency identification (RFID) reader applications. The proposed antenna consists of four meandered monopole elements fed by a series feed network, each segment having an equal magnitude and a successive 90°phase difference. The monopole elements and the feed network are created on two separate printed circuit boards. Four coaxial lines are used to connect the feed network to the monopoles. Short-circuited tuning stubs are employed for impedance matching. A prototype antenna measuring 45 × 45 × 9 mm3and weighing 13 g is designed, fabricated, and tested. Measurements show that the fabricated antenna has at 919 MHz a gain of 2.2 dBic, a 3-dB gain beamwidth of 150°, and a 3-dB axial-ratio beamwidth of 146°.