A NOVEL DOUBLE-LAYER MICROSTRIP ANTENNA ARRAY FOR UHF RFID

A novel RFID reader antenna is designed for UHF band. The proposed antenna consists of double-layer two elements rectangular patches and impedance tuning stub. The lower-layer patches are the chief radiation elements. The upper-layer patches could perfectly improve impedance matching and broaden impedance bandwidth. Meanwhile, the antenna adopts series-fed at one edge to simplify the feeding-net. The simulated and measured results demonstrate that the proposed antenna has a lower VSWR (<= 1.2) in a wide bandwidth (882-945 MHz, 6.88%), which greatly covers the operated band (902-928 MHz). In H-plane, the gain gets 11.45 dBi and 7.15 dBi at 0 degrees and +/- 50 degrees. respectively, that could make the reader have a farther identification distance in the horizontal direction in the case of vehicle identification.