Study On The Design Of Chipless RFID Tag Based On Amplitude Coding

Radio frequency identification(RFID)is a kind of technology of identifying targets,which using radio frequency signal to read the target storage information.It has been widely used in many fields,such as the cargo circulation,libraries and so on.Compared with the bar code technology,the cost of RFID tags is still high,which makes the application of RFID seriously constrained.In this case,chipless tag was raised.The chipless tag is designed as a series of different electromagnetic scattering structures to recognize the label by the difference of the scattered signal itself.If the scattered signal of a resonant structure will appear on a peak in its resonant frequency point,then the presence of peak can be used as the encoding of the two states.However,the spectrum utilization rate of this method is not high.If the scattered signal waves are encoded at different amplitude levels,the efficiency of the spectrum can be effectively improved.First,an "L" shaped slot resonator is designed in this paper.The different positions of the "L" shaped slot in the tag resonator lead to different RCS amplitude levels.Based on this resonator,the tags with about 7bits capacity are designed.Then,a tag resonator based on fractal technology is presented.The element structures are deformed using fractal technology,and the length of slot in the cell structure is adjusted so that the resonators can work at the same single frequency with multiple RCS amplitudes.Based on this resonator,the tags with about 8 bits capacity are designed.The third chipless RFID tag is based on the cross-ring slot structure.The tag resonators adopt cross-ring slot unit structure.By adjusting the width of the unit structure multiple times,the cell structure is adjusted so that the resonators can work at the same frequency with a variety of RCS amplitude.The tags which are presented can be multi-bit coding on amplitude at the same resonant frequency,so it improves the band utilization and coding efficiency,simplifying the requirements of the card reader.As the tag resonator can work at the same single frequency,and the occupied band is narrow,which improve reader's sensitivity and simplify the circuit structure.Due to the symmetrical structure of the resonator,the tags are not sensitive to the direction of polarization.