Simple Patch Antenna Design with Multiple Linear Polarizations for RFID Readers

This paper proposed a compact antenna with multiple linear polarization realization for radio frequency identification (RFID) operating at ultra-high frequency (UHF) band. The main radiator is a crossed patch, which is excited by different feeding positions to adjust the current flowing on the patch. To minimize the unwanted effect of the biasing circuit on the antenna radiation performance, the antenna is excited through a reconfigurable feeding network with one input and three outputs. By controlling the ON/OFF states of three PIN diodes integrated into the feeding network, four different modes including horizontal, vertical, and both diagonal polarizations can be realized. The final antenna design with overall dimensions of 0.67 0.67 0.04 at 915 MHz shows good matching performance from 910 to 925 MHz. Within this band, the broadside gain values for all polarization states are better than 6.2 dBi.