U-shaped slot-array antenna for RFID shelf in the UHF

This paper presents a linearly polarized slot-array antenna that consists of slots series-fed by a microstrip line for RFID shelf applications in the UHF band in which the end of the line is shorted to the ground plane by the via-hole. The radiating element of the antenna is the U-shaped slot fed by the travelling and standing current wave formed on the microstrip line left shorted-end. The gain of the designed 3×6 slot-array antenna is about 4dBi and the fractional return-loss bandwidth of less than -10dB about 5.5% at 920MHz.