| The wireless passive RFID technology that based on the surface acoustic wave is one of the focus of the sensor field in recent years. It has the advantages of the wireless, passive, identification distance, can realize the recognition of the high-speed moving objects and can adapt to the complex environment, thus cause the attention of the researchers.In this article, the detection system of the wireless passive RFID in the dynamic environment is carried on the thorough research. Theoretically it expounds the operating principle that the wireless passive RFID tags can be detected effectively in a dynamic environment and by making the fast frequency sweep reader to read the tag smoothly under the dynamic environment.First of all, the article analyzes the recognition principle of passive tags in a dynamic environment. Through the time domain analysis of the FMCW emission signal and the echo signal, it analyzes the conditional hypothesis of the intermediate frequency signal and derives the key method to identify the sensor tag in dynamic environment effectively.The second, it presents the scheme of the fast scan reader that includes hardware implementation and the program implementation. The hardware part of the fast scan reader is divided into the transmitting part, the receiving part, the signal processing part and the system power source part. The transmitting part is composed of the fast FMCW signal source, the power amplifier, the automatic gain antenna and the circulator; The receiving part is composed of the low noise amplifier, the mixer, the circulator and the antenna; The signal processing part is composed of the analog digital converter and the digital signal processor. The power system consists the self recovery fuse, the EMI filter, the analog circuit and the digital circuit power supply; The fast frequency sweep reader program is divided into the single chip microcomputer control program, the signal processing program and the overall system control program. The MCU control procedures includes the PLL initialization procedures and the sweep frequency procedures, the DDS initialization procedures and the sweep frequency procedures; The signal processing program includes the data window, the end of the data sequence, the fast Fourier transform, the peak value, the calculation code and so on; The overall control program is the running process of the system.At last, the system is tested and analyzed comprehensively, including the test of the transmitting part and the receiving part of the fast scan reader and the test of the sensor tags in the static and dynamic environment, finally it gives the detailed test results and analyzed the results reasonably. |
