Microstrip Antenna Design For 915mhz Rfid System

Because of many outstanding structure advantages the microstri p antenna has become the main current development direction of an tenna, and the traditional testing methods like full-scale making are gradually replaced by modern computer simulation and verification using the numerical calculating method on electromagnetic model, it makes the time and costs of engineering design from designing to realization shorten. This paper discuss the design of microstrip pat ch antenna array for 915MHz RFID asset management system, and the process of simulation and verification based on the electromagn etic simulation software HFSS which use the numerical. analysis me thod FEM.First, the paper makes a brief introduction including source, ba ckground and research situation of the project, and then gives some expositions and explanations about the microstrip theory and formu las which is involved in the coming paper. Second, according to th e research object, focusing on the require indicators of antenna that using in RFID asset management system, we design a rectangle m icrostrip patch radiation unit working in 915MHz frequency and the impedance matching feeding structure of quaternary planar array b y the classical transmission-line theory and formulas. We also desig n the impedance match feed system for two feeding modes which a re called microstrip line-fed and coaxial probe-fed and take a simpl e comparison between them. The line-fed mode is easier to compos e array which is uniform and the key point of which is to design a feed network that transmits the same excitation wave on amplitud e and phase to every single chip. Third, according to initial parame ters, the paper discuss the following steps of modeling, setting, veri fication calculation and optimization in the computer-assistant design software HFSS. We make adjustments on parameters by using the function of optimization through the simulation results, and finally t he antenna performance indexes meet the requirements put forward previously, and satisfy the real application condition for RFID syste m. The last, we make summaries and prospects about the research achievement, and point the deficiency and the coming work of impr ovement.