A Coupled-fed Compact Size UHF RFID Reader Antenna with Parasitic Slotted Element

In this paper, a coupled-fed slotted antenna for ultra-high-frequency (UHF) radio frequency identification (RFID) reader antenna is proposed. In this case, the antenna has a planar size of $80\ \mathbf{mm} \times 64\ \mathbf{mm}$, and it is standing vertically on a small ground plane of size $80\ \mathbf{mm} \times 39\ \mathbf{mm}$. To increase the impedance bandwidth of the proposed reader antenna, so that it can works within the required 902–928 MHz band for UHF RFID, a stepped type feeding structure is utilized, and it is coupled to a parasitic element. The parasitic element is loaded with two open-end slots for increasing the electrical path, so that is can achieve compact size at a lower frequency. The measured result has shown that the proposed antenna can yield a 10-dB impedance bandwidth of 3.6% (897–930 MHz).