Microstrip patch antenna array for range extension of RFID applications

In this paper, an UHF band 2times2 microstrip phased antenna array is designed for extending the range of an RFID reader system. The phased antenna array operates at the frequency of 867 MHz, as specified in Gen2 protocol European standards. The phased antenna array has four microstrip patch antennas, three Wilkinson power dividers and a transmission line phase shifter printed on the same Arlon AD450 substrate with a dielectric constant of 4.5 with dimensions of 34times45 cm. The phased array antenna has a measured directivity of 9.5 dB and the main beam direction can be switched between the angles of plusmn 40 degrees with a 3dB beamwidth of 90 degrees. The phased antenna array can be used to extend the RFID system working range.