Abstract
In recent years, RFID systems have received much attention in information management and security. For evaluation of RFID systems, study of electromagnetic wave propagation and scattering of UHF wave and microwave transmitted from tag antenna to reader antenna in in-door and out-door is indispensable. In this paper, we describe the characteristics of electromagnetic wave scattering, diffraction and interference by obstacles in propagation channel and show the distribution of received level using FDTD method. In RFID systems, receiving characteristics are strongly influenced by the structure of roads and buildings for out-door environment and rooms, doors and windows for in-door environment. Three-dimensional numerical analysis is studied to evaluate the effects of the earth of roads and building with finite heights for out-door applications and effects of ceil and floor of buildings for in-door applications. Signal processing and control are important to recognize each tag code correctly even if multiple codes from tags are received by a reader simultaneously. In this paper, received characteristics when multiple tags transmit signals modulated by ASK are studied by FDTD method and compared with the analytical results.
