Broadband UHF RFID tag antenna with quasi-isotropic radiation performance

Based on the theory of microstrip antenna design and electromagnetic radiation, a kind of tag antenna with a bent meandered dipole and two short-circuited strips is studied in ultra high frequency (UHF) RFID bands to provide broadband and omni-directional performance simultaneously. The proposed antenna was fabricated with a thin copper layer printed on a thin lossy PET substrate for low-cost production. Our simulation and measurement results show the proposed antenna provides a quasi-isotropic radiation pattern and can obtain 200 MHz bandwidth under the condition of voltage standing wave ration (VSWR) less than 2, which is 1.5 dBi for worldwide UHF RFID bands. It is confirmed this kind of antenna is suitable for all different UHF RFID tags in passive RFID applications.