The Circularly Polarized Corner-Truncated Rectangular Patch Antenna with Double Slits for UHF RFID System

This paper presents a circularly polarised rectangular patch antenna for ultra-high-frequency (UHF) radio frequency identification (RFID) applications using for Thailand standard. The antenna consists of a corner-truncated patch with double slits and a ground plane. The rectangular patch is fed by a single probe. The circular polarisation can be achieved by using three techniques such as adding double slits, using square shape and using a slanted cutting corner. The antenna has a compact size and appropriate for RFID system of Thailand standard. The measurement results show that |S11| (dB) is less than -10 dB. The antenna gain is 8.83 dBic with the unidirectional radiation pattern. The 3-dB axial ratio beamwidth is 65º over the frequency band of 914.4 - 929.9 MHz covering the UHF RFID applications for Thailand standard