Study And Realization On Key Techniques Of Long Distance HF Radio Frequency Identification

In the information stage, the corporations depend more and more on the information operating system. No matter the inside operation or the outside cooperation, once using the information system, it will involve identification of personnel or commodity data collection (information exchange). So the influences of auto identification become much greater nowadays. The bar code technology is the primogenitor of auto identification, but less and less adapting to the development of information automatization. The RFID (Radio Frequency Identification) technology is a novel information technology, and become more and more important in auto identification system.In practical application, UHF (915MHz) RFID technology is sensitive to material containing water, and it doesn't apply to wet circumstance. Because the UHF signal is high frequency and short wavelength, it can easily be absorbed by the material containing much water. It causes the weakening of the energy and the decline of the performance. However, the long distance HF (13.56MHz) RFID signal is low frequency and long wavelength, so it's not sensitive to the material containing water. Then it can overcome the shortcoming of UHF effectively. The internal retail, medicine and logistic have high demand of the application of long distance HF RFID technology. Therefore, the research of such subject will bring preferable economy and social benefit.Firstly, the radiate model and performance parameter of the frequency identification system antenna are analyzed from the electromagnetic filed and energy transmission. Using the classical theory of electromagnetic induction, the paper discusses the essence of the long distance HF radio frequency identification system and derives the calculation method of the key system parameters. Also the two basic communication methods of passive RFID system are discussed.Secondly, the characteristic of baseband signal and frequency band signal in RFID system are analyzed. The features of channel noise and interference, and the signal potential influence factors are showed in this section. Then discuss the weak reflective signal detection method of loose coupling and bring forward the effective signal enhanced and noise filtered method. Furthermore, use the wavelet analysis method to improve the detection sensitivity.Thirdly, investigate the loop antenna as the major object and bringing forward several optimizing schemes for reader antennas. Also the calculating and measuring...