| Radio frequency identification(RFID) is one kind of the non-contacttype automatic identification technology. This technology uses radiowaves carrying information stored about the identified object orcommands to identify objects via space electromagnetic coupling. Radiofrequency identification system mainly includes tags, readers, middlewareand so on. Radio frequency identification technology has manyadvantages, with the development of radio technology and the continuousimprovement of manufacturing techniques, RFID technology graduallyreflects the advantages, in freightage and supply chain management,manufacturing, transportation, public safety and other areas, RFIDtechnology reflects the tremendous value.This makes radio frequencyidentification system for the study and design of the antenna into atheoretical and practical value of an important subject.First of all,this article begins with a brief introduction of the radiofrequency identification system-related knowledge, and particularlydescribes the system of radio frequency identification and classification ofthe working principle. At the same time introduced the classification ofRFID antenna and the main performance indicators.Secondly,the basictheory of microstrip antenna is introduced,such as the definition and the basic structure of microstrip antenna, at the same time introduces the threecommonly used microstrip antenna analysis method, (Transmission linemodel, cavity model, finite element method), through analysis andcomparison of three methods , determined using HFSS finite elementmethod for the analysis of the antenna design,provide a theoretical basisfor the follow-up.Through the analysis and research of multiple antenna model, designedan antenna which applies to long-range radio frequency identificationsystem using coplanar waveguide-fed slot antenna model as the basicstructure of the antenna design in this paper ,the general model structuredivided into the metal flooring, coplanar waveguide feed belt and feedsource.The use of non-symmetry metal floor structure can enhance theantenna bandwidth characteristics , add a round side at the coplanarwaveguide band terminal as feed source , and further improve thematching characteristics of antenna and bandwidth characteristics byincrease circular slotted feed structure and the metal side.Test the antennadielectric substrate thickness of 1.0mm, 1.6mm, 2.0mm by usingsimulation software HFSS on the simulation results of the standing waveratio, return loss, gain and other parameters. the final comparative analysishas been done to determine the antenna dielectric substrate thickness of1.6mm, the simulation results are very good, but the polarization characteristics is not ideal, therefore the coplanar waveguide-fed slotantenna model has been improved .Through the analysis and research of long-range radio frequencyidentification system and antenna structures, the slotted structure has beenchanged, at last analyzes the long-range radio frequency identificationsystem of the antenna structure, through the application of the value of theresearch, a final decision has been made to design a coplanar waveguidefedmicrostrip antenna which works in the 5.8GHz of the resonantfrequency in UHF, the antenna parameters have been simulated andanalyses by the use of electromagnetic simulation software Ansoft HFSS,including antenna VSWR, return loss, gain pattern, gain frequency graph,the antenna impedance, the antenna axial ratio and so on, making theconclusions that Slotted structure can affect the change in bandwidth andpolarization characteristics of antenna, providing the basis for the futuredesign of similar antenna. Through testing the antenna parameters ,thefinal design of the structure can achieve a small, ultra-bandwidth, low-cost,high-gain, omni-directional, and good mechanical design objectives. Theresult is much better.Due to the time constraints and other objective conditions, this articleonly designed the model of the antenna and software simulation, a lot ofwork has to been done for the practical application, and the simulation hasbeen carried out under ideal, in practical applications should note the following:1)Due to the frequency of the antenna is very high , the antennamanufacturing and materials requirements for the standard is also high, thehigh-precision measurement instrument has to been used to achieve thedesired effect of the simulation.2)In order to further enhance the antenna standard for the long-range radiofrequency identification systems,the performance has to been improved tomeet the higher requirements,such as antenna miniaturization, low-cost,polarization characteristics, as well as gain, etc.Because the antenna is more and more application areas, the cost of theantenna, the antenna size, polarization characteristics, gain characteristicshave become more sophisticated, taking into account various requirementsof integrated design, the design of the antenna which not only demandsexcellent performance but also needs to meet the actual production of thelong-range radio frequency identification system will be a trend. |
