Miniature and Near-3D Omnidirectional Antenna Based on Simple Structure for UHF Band RFID Tag

A novel planar and miniature ($0.14 \times 0.1 \times 0.002$ $\lambda ^{\mathbf{3}}$) UHF band RFID tag antenna is proposed whose radiation pattern is near-3D omnidirectional. The proposed antenna is comprised of two open-loops who are mirror symmetrical to the substrate. The proposed antenna is easy to change its shape in order to match different chips without making great impact on performance. Simulated operating 3 dB bandwidth of the antenna is near 29 MHz and the gain deviation is less than 1.7 dB.