Design of Small Low-Profile Universal UHF RFID Reader Antenna

A small low-profile linearly-polarized patch antenna is proposed for universal ultra-high-frequency (UHF) RF identification (RFID) applications. The antenna is composed of a folded patch and an improved L-shaped feeding strip. It works from 834 to 970 MHz with SWR less than 2, thus the proposed antenna is universal for UHF RFID applications worldwide at the UHF band of 840-960MHz. Moreover, the air thickness of the patch antenna is 20mm, reduced to only 0.06λ. Stable unidirectional radiation patterns, low cross-polarization level and stable gain are achieved over the pass-band.