Research Of Detection Technology For High Sensitivity Radio Frequency EAS

In the era of prosperous market economy,almost all shopping malls and supermarkets take an open shopping environment to facilitate customers to shop.This kind of sales method promotes consumption and facilitates consumers to purchase goods,but also brings the problem of product security to the store operators.Electronic goods anti-theft systems are increasingly being applied to supermarkets to solve the growing problem of commodity theft to reduce the loss of merchants.Since the birth of the electronic goods anti-theft system in the United States in the 1960 s,the research on EAS has not stopped,and has gradually become one of the key research areas of security industry.At present,the common EAS system in China adopts a hardware design mode in which the transmitter and the receiver are separated.This method has the disadvantages of small detection coverage area and high use cost.The system software design adopts the front-end design mode.In this way,the utilization rate of the main control chip is not high.,detection of low real-time defects.This thesis mainly studies the radio frequency EAS detection technology,and designs a transceiver integrated RF EAS detection system based on TMS320F28335 as the main control chip.When working,the system will form a symmetric electromagnetic field in the space on both sides of the antenna to double the detection area and effectively reduce the detection blind area.The design can improve the detection performance;in the system,the embedded real-time operating system DSP/BIOS cutting and transplanting is realized,and the thread dynamic scheduling is realized according to the task thread priority,which greatly improves the working efficiency of the EAS system;the system sweeping signal center frequency is 8.2MHz,sweep frequency bandwidth is 0.5MHz,and the sweep interval is 6.25 KHz.The received electronic tag signal is first filtered by the filter to remove out-of-band noise,and the demodulator is down-converted into a low-frequency signal for A/D.The digital signal is sampled,and finally the digital signal is processed and judged.In order to ensure the performance of the system,a hardware filter that conforms to the characteristics of the electronic tag signal is designed to suppress the interference of external noise.In the tag identification algorithm,multi-feature joint judgments such as software mean filtering,signal strength statistical analysis,and spectrum analysis based on Fast Fourier Transform are used.In the final decision,the multi-threshold joint judgment method is used to judge whether the tag is invaded or not.Improve the reliability of the judgment.Finally,the hardware prototype production and test platform of the designed system is completed,and multi-scene performance testing is performed.The test results show that the system can realize the detection distance of 124~140cm on one side of the electronic hard label and 248~280cm on both sides.The detection distance of the electronic soft label is 88~96cm on one side and 176~192cm on both sides.The system can achieve continuous and stable operation,with good anti-interference performance,and the false negative rate is less than 5%.