Research And Simulation Of RFID Planar Spiral Coil For Detection Of Milk Freshness

Milk is a common source of nutrition in daily life, but problems on milk quality has been frequently reported. Nowadays, existing milk detection technology has the disadvantages of contact measurement, large measuring instrument, High detection cost, needing professional operator and so on. The research of this topic, with radio frequency identify(RFID) technology, on detecting the freshness of milk, is characterized by being passive, low cost manufacturing, selected response, non-contact measurement and small size.In this paper, with the theoretical, emulational and experimental methods, the effect of the frequency of the RFID antenna in the process of milk storage is studied, and a radio frequency identification system, used to manage milk information, is designed and implemented.A lumped circuit model is established for the coupling of radio frequency antennas in milk environment. With a tag being attached to the surface of the milk cartoon, parasitic capacitance is generated between the tag and the milk box and the milk, which is directly related to the dielectric properties of milk. When the dielectric properties of milk changes, parasitic capacitance then changes, which eventually leads to the frequency offset of the RFID antenna. Simulation is done with full wave 3D electromagnetic simulation software(High Frequency Structure Simulator, HFSS). A sensitive antenna design method for milk modification is proposed, and the RFID 13.56 MHz coil antenna is designed. The basic model of milk is established, and the characteristics of different dielectric properties of milk in RFID magnetic field are analyzed. In the experiment, a vector network analyzer and a pair of radio frequency identification antenna are used to detect the freshness of milk. Theoretical modeling, simulation modeling and experimental results show that during the storage under normal temperature, with the dielectric properties of milk changing, the resonant frequency of the antenna increases gradually; in succession, dielectric properties of the milk stored at room temperature almost have no change and, therefore, there is no influence to the resonant frequency.The research results of this paper provide a theoretical basis and reference for the use of radio frequency identification technology to detect the freshness of milk.