Study In The Optimization Of Radio Frequency System And Signal Identification Algorithm

Electronic article surveillance systems were widely used in supermarkets, warehouses etc. for theft protecting. The paper was based on implementation and potential exploitation of a radio frequency EAS system. The contradiction encountered in EAS system commonly existed in any detecting and alarming systems: the higher detecting rate and the lower false alarming rate. In most of the cases, we can't obtain both of them.At first, a survey in EAS design area was provided at length. The pros and cons of six categories of EAS technology were discussed. Five instances based on MCU AT89C51, Microchip PIC and DSP TMS320F206 were analyzed carefully. Some useful concepts in radar technology, such as CFAR were adopted as software strategies.After that, we purposed a concise and inexpensive hardware scheme. 8-pin MCU PIC12C508A was chose as a wave generator in the transmitter. 18-pin MCU PIC16C711 worked as a tiny DSP in the receiver. The whole procedure from transmitter magnetic field, pickup, detecting to filtering was calculated and visualized with the aid of MATLAB.The recognition in EAS systems was not blind recognition. It was a preplanned activity of activation and respond. The characteristics of tag signal should be made full use of. Five characteristics of the tag signal were concluded as the criterions in recognition. They were: intensity, periodicity, symmetry, stabilization, punctuality.Our algorithm was based on simplified self-relation operation combined with dynamic threshold regulation and peak detecting. Its false alarming rate were evaluated and charted by MATLAB. Further artificial neural network experiments output poor results. A major difficulty were the obtaining of train data at various circumstance.In embedded software debugging, the register information could be viewed through 8 bits LED bargraph and one button. 29 suggestions on 4 aspects were proposed to improve the whole performance of EAS system: transmitter, analog part of receiver, digital part of receiver, software.Finally, we took a look at the prospect of RFID technology, a successor of EAS and barcode.