A Universal UHF RFID Reader Antenna

A broadband circularly polarized patch antenna is proposed for universal ultra-high-frequency (UHF) RF identification (RFID) applications. The antenna is composed of two corner-truncated patches and a suspended microstrip line with open-circuited termination. The main patch is fed by four probes which are sequentially connected to the suspended microstrip feed line. The measurement shows that the antenna achieves a return loss of -15 dB, gain of 8.3 dBic, axial ratio (AR) of 3 dB, and 3-dB AR beamwidth of 75^deg over the UHF band of 818-964 MHz or 16.4%. Therefore, the proposed antenna is universal for UHF RFID applications worldwide at the UHF band of 840-960 MHz. In addition, a parametric study is conducted to facilitate the design and optimization processes for engineers.