Analysis And Research On Antenna Radiation Field Of RFID System

With the development of RFID technology, the radiation field between the reader antenna and the tag will become a new hotspot for research. Many phenomena and problems in RFID application have something to do with radiation field, but research on antenna radiation field of RFID system is scarce at present. The theory of electromagnetic field and RFID technology are combined in this paper and some exploring work for research on RFID antenna radiation field and RFID application is done.By the research means such as theoretic analysis, modeling, simulation and actual measure, the work in this paper are as follow:1. The books and literature about the theory of antenna and electromagnetic field are read comprehensively and systematically, the theory is combined with RFID technology and the theoretical basis needed in analyzing antenna and radiation field is compiled.2. For the dielectric is an important factor to influence antenna performance and electromagnetic wave propagation, a new way to measure the dielectric constant is put forward on the base of existent method. Experiments prove that the results' errors are within permission.3. The three ideal models in ISO 18046: anechoic chamber, anechoic chamber with a conductive ground plane and open area test site are introduced. Then on the base of the three ideal models, a semi-open test site: corridor model is found. An effective analyzing way: ray-tracing method is introduced, its theory is explained and the calculation formulas are given.4. The theory of antenna and radiation field is applied to practical case: the problem of interference between adjacent driveways in RFID ETC system. Three solutions: time division, frequency division and space division are put forward. Timedivision is introduced simply. As for frequency division, the effect of frequency hopping is analyzed from the angle of field distribution. For space division, a microstrip antenna array whose lobe width is very narrow is designed on the base of a four-element antenna. Their directivity diagrams are simulated in HFSS. The results prove that the lobe width becomes much narrower and the directive coefficient and gain increases obviously. The result of actual measure is the readable range is 20 meters long and 4 meters wide.