Based on basic working principle of passive UHF RFID system

propose a new type tag which intoduces phased array antenna to make the tag has function of positioning and can improve communication distance of UHF RFID system. Theoretical and numerical analysis on parameters of tag phased array antenna is done

for different number of antenna array element and different element space

magnitude and direction parameters of the antenna beam are simulated by Matlab. Simulation results coincide with theoretical analysis.Appropriate parameters of phased array antenna is determined by simulation

which lay theoretical foundation for further study and design.