A planar reversed log-periodic UHF near-field antenna for RFID application

A planar reversed log-periodic near-field antenna is proposed for ultra-high frequency (UHF) radio frequency identification (RFID) application in this letter. The proposed antenna is composed of two planar reversed log-periodic dipole antenna (LPDA) units. The concept of two closely spaced, oppositely directed currents (ODCs) and the design guideline of LPDA are adopted to achieve strong and uniform magnetic field in the near-field zone of the antenna with a broad bandwidth. The proposed antenna is printed on a 170×170×1 mm³ FR4 substrate. Except strong and uniform z-orientation magnetic field (Hz), the simulated results also show the antenna can achieve a broad bandwidth of 133MHz (833-966MHz) as well.