L-shaped probe feed patch antenna with circular polarization radiation for UHF RFID applications

This paper proposes a patch antenna for Radio Frequency Identification (RFID) applications in the 900 MHz (902-928 MHz) Ultra High Frequency (UHF) band. To achieve optimal impedance matching and 10-dB operating bandwidth at the desired band, the L-shaped probe feed technique is employed as the feeding mechanism of the proposed antenna. In this case, a semi-circular parasitic patch and a slit are loaded into the main radiating triangular patch, so that good circularly polarized (CP) radiation can be generated from the proposed patch antenna. Here, 10-dB impedance bandwidth and 3-dB AR bandwidth of 19.88% (847-1034 MHz) and 4.3% (891-930 MHz) are achieved. Furthermore, stable gain variation of approximately 7 dBic is also exhibited across the desired RFID UHF band.