M.Sc. Tezi Görüntüleme
Radio Frequency Identification(RFID) systems have been taking a strong interest from many industrial applications, that it smoothly solves many tag reading, identifying, positioning etc. Three kinds of RFID systems are widely accepted by the industry. First Low Frequency (134 Hz) system which is based on magnetic coupling from very short distances (0-10 cm) have been used for almost 20 years. Secondly, High Frequency (13.54 MHz) system which is used for sort distance contactless reading over 30 cm and the most popular RFID systems for personal identity and item markings, have been recently introduced to application areas. The third system is the UHF (868-915 MHz) RFID system which is used with pure electromagnetic coupling over relatively long distance, up to 7 meters and it is quite new to market having no more than a three years of history. But, the UHF RFID system happens to be the most desirable system by industry for more than one reason. Along side to these passive RFID tag systems, a wide range of active RFID systems have been used for toll readings, parking, vehicle identifications where the power is not a problem.Therefore the current trends show that RFID systems are going to be widely used in the industry with the market increase rate of %120, starting from bar code replacement. In particular research on the passive UHF RFID systems continuing and a standard yet to be finalised since it covers longest distance, uses smaller antenna etc. However, because of the essential of UHF system, its signal travels longer distance with high energy therefore when considering an indoor environment, vehicle or market place, the use of more than one RFID reader system would not be possible. On the other hand RFID reader system may have well be responded by an unwanted tag from a log distance. Therefore an interference analysis and propagation model for the RFID systems should be obtained before the system installation.
This thesis considers an experimental analysis of propagation and fading profile of an UHF RFID systems. It deals with antenna design, multipath fading, multipath spreading and signal attenuation of items(things) (i.e. wall, door, glass etc.).
The thesis is concluded with exhibiting interference level over the measured site, in order to guide an RFID insulation system or avoid its effects.
Key Words: RFID, Tag , Reader , Electromagnetic Waves, Electromagnetic Propagation, Attenuation, UHF Band, Channel Measurement , Channel Coefficient.