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UHF RFID reader using slanted slot patch metasurface on microstrip patch antenna

In this paper, a slanted slot patch metasurface (MS) is placed over microstrip patch antenna for Ultra High Frequency (UHF) radio frequency identification (RFID) reader. With effective parameters on permittivity and permeability of metasurface, a mu near zero features is obtained over the operating frequency range of universal RFID system. The MS property is used to improve the antenna performance such as gain. Then, oblique slot structure of unit cell on MS can provide and support the circular polarization (CP) of the proposed antenna. The measured results perform that the antenna has impedance bandwidth of 8.08% (854-928 MHz), axial ratio bandwidth (ARBW) of 4.37% (895-953 MHz), and a realized gain level of 5.1 dBi. It is clearly suitable for Thai UHF-band (902-928 MHz).