TAILIEUCHUNG - Radio Frequency Identification Fundamentals and Applications, Design Methods and Solutions Part 9

Tham khảo tài liệu 'radio frequency identification fundamentals and applications, design methods and solutions part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 192 Radio Frequency Identification Fundamentals and Applications Design Methods and Solutions Fig. 11. Signal in the winding of the tag. Fig. 12. Signal in the reader after the demodulation in the first lock-in amplifier. Figure 13 shows the signal after the second lock-in amplifier. It has the same frequency that the signal produced by the microchip in the tag. It means that a signal with the same frequency that the produced in the PIC of the tag has successfully obtained in the reader. Fig. 13. Signal in the reader after the demodulation in the second lock-in amplifier. These graphs Figures 11 12 and 13 clearly show that the microcontroller in the tag can be powered by a low frequency magnetic field and it can send information. They also show that the fluxgate with the second in-phase demodulation has successfully used as a reader. Theoretical model In Ciudad Rio-Perez et al. 2008 it is given an accurate model to calculate the distance limitation of the ULF RFID system for a particular application. The model is also compared RFID in Metal Environments An Overview on Low LF and Ultra-Low ULF Frequency Systems 193 with experimental data. This distance limitation can be due to failures in the detection or in powering the tag. Detection of the tag minimum sensitivity of the reader fluxgate sensor . The magnetic field in the tag position Hex is assumed to be sinusoidal with amplitude H0 and angular frequency ffl Hex Hoej Bt 5 The magnetic flux through the tag and the induced . in the winding are easily calculated. See Ciudad Rio-Perez et al. 2008 for a detailed deduction. This . is used to charge the capacitors that power the microcontroller. When the PIC in the tag short-circuits the winding the induced . gives rise to the flow of a current through the winding. This current causes a magnetic field. The total magnetic field HR that magnetizes the magnetic core of the tag is the addition of the magnetic fields produced by the antenna Hex and .

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