An Inverted-F Antenna for RFID Tag Mounted on a Full Container of Liquid

This study developed a novel inverted-F antenna for radio frequency identification (RFID) that mounted on a high dielectric materials (liquids). Conjugate matching of the resistance and inductive reactance of the antenna to the desired chip impedance can be performed by simply tuning the distance between the stub and the side strip of the feed loop. An Alien Higgs-4 chip (8.5 - j151 Ω at 915 MHz) was connected to the center of the side strip of the feed loop. The space between the proposed antenna and the high dielectric materials enhanced antenna gain by increasing reflection from the materials. After analysis and optimization of the tag antenna, fabricated tags mounted on a container of water had impedance bandwidths of 4.1%. In tests of an RFID reader with an effective isotropic radiated power (EIRP) of 4.0 W, the maximum read ranges for tags in an outdoor environment was 5.7 m. Measurement data agreed with simulation results.