A Low-Profile Antenna With Quasi-Isotropic Pattern for UHF RFID Applications

This letter presents a simple low-profile antenna for active UHF radio frequency identification (RFID) applications in the North American band. The antenna has a simple layout and a quasi-isotropic radiation pattern. The antenna layout consists of a bent dipole with a T-matching network and a ground plane with two slots. These features produce a pair of crossed electric and magnetic dipoles, which collectively produce a quasi-isotropic radiation pattern. The simplicity of the layout facilitates electronic circuit placement necessary for operation of an active RFID tag.