Radiation analysis of an equivalent magnetic UHF-RFID tag located on a coated metallic sphere using UTD method

Abstract

The radiation analysis of an equivalent magnetic UHF-RFID tag antenna located on a coated metallic sphere using UTD method is illustrated in this work. The conventional UHF-RFID tag can be represented by electric current source and is designed by employing the dipole antenna concept. The electromagnetic (EM) radiation characteristic of UHF-RFID tag mounted on the metallic and material coated metallic curved objects can be distorted because the electric field is parallel to the metallic surface. It is very important to include the metallic objects when designing the UHF-RFID tag. In this work, the uniform geometrical theory of diffraction (UTD) method is employed to predict the EM radiation characteristic of the electric current source and equivalent magnetic current sources mounted on a coated metallic sphere. It is noted that the equivalent magnetic current source provides broader beamwidth. This makes the communication area wider than the electric current source case. An example of UHF-RFID tag is designed in this work based on the equivalent magnetic current source or slotted antenna concept. The calculated result is confirmed by comparing with the CST Microwave studio simulation. It is confirmed that the UTD method is suitable for the radiation calculation of the tag mounted on material coated metallic curved objects.