| Electromagnetic field exists in all aspects of human life and affects human survival and development.Human beings have been committed to the use and monitoring of electromagnetic fields,especially in some special fields,such as military reconnaissance,industrial production and so on.At present,the vast majority of electromagnetic field monitoring equipment has a good measurement accuracy,but due to its large size,high power consumption,high cost,and the need for human intervention to complete the monitoring,so it is not suitable for some special occasions to carry out high-precision,high-frequency,high intelligent monitoring of electromagnetic field.This paper combined RFID(radio frequency identification)technology,which has developed rapidly in recent years,with electromagnetic sensing technology,making full use of the advantages of low cost and easy deployment of RFID technology to realize passive wireless electromagnetic field measurement tag for electromagnetic field monitoring,finally a wireless electromagnetic field measurement system was constructed.The main research results of this paper are as follows:1.Passive impedance type electromagnetic field sensor is integrated in passive wireless RFID electronic tag,and a low power consumption and high stability 200 kHz active crystal brace is used as the excitation source of the electromagnetic sensor;based on operational amplifier,bandpass /low-pass filter and detector realize low-power,high signal-to-noise ratio electromagnetic field sensing circuit,and realize high-precision sensing of electrostatic magnetic field(0 Hz)and alternating electromagnetic field(50 Hz-60 Hz).2.Design miniaturized,high-efficiency energy collection and power management circuits to achieve energy self-sustainment of tags.The designed and implemented rectifier circuit for 920 MHz-925 MHz frequency band,the rectification efficiency can reach 50% when the input power is 3 dBm.The two-level micro-power LDO cascade structure is used to provide a high-precision DC power supply for the tag to ensure the high stability of the electromagnetic field sensing signal.The fluctuation of the sensing data of the final test result is less than 0.5%.3.Realized the design and layout of the label's anti-strong electromagnetic interference,designed the label shielding cover based on white copper material,to make ensure the label can work normally in the strong electromagnetic field(H?100Oe;E?400kV/m).4.Selected the MSP430FR5969 microcontroller as the carrier of the protocol implementation,realized all mandatory commands stipulated in the ISO/IEC18000-6C communication protocol,finally achieved to communicate with the UHF RFID reader.Moreover,by adding special parameters to Read command customed electromagnetic acquisition instruction,finally realized the perception and measurement of the magnetic field parameters..5.Constructed a wireless magnetic field sensing system with UHF RFID reader and host computer,and obtained the magnitude of the static electromagnetic field through experiments.The passive wireless magnetic field sensor tag developed in this paper has a broad space for secondary development,which is suitable for power plants,power transfer station and other large electricity production and transmission equipment to monitor electromagnetic field with the advantage of low power consumption,low cost,long distance,high precision.At the same time,it provides a plate-level verification platform and experience for the development of such passive wireless sensor tag chip. |
PDF Full Text Request