Research Of Chipless RFID Tag Based On The Technology Of DGS

RFID is a radio frequency identification which begins to apply in business on a large scale in the1990. RFID has the anvantage of small size of tag, high scanning speed, large capacity of data and reliable security. It has been used in transportation, logistics management and medical industries. RFID system mainly includes RFID tag, card reader and computer and RFID tag decides the design principle of the other two modules. Since the memory chip inside is the costliest part of the tag, it is the key problem restricting the development of RFID. Because the operation of the chipless RFID doesn’t need memory chip, it has the lower cost and better prospect of development. Chipless RFID tag has become a hot research field of RFID. This article studies chipless RFID tag mainly from the following aspects.The first part discusses the system composition and working principle of chipless RFID tag, analyes the code label in detail based on frequency characteristics, and summarizes the designment principles of tag:realizing multi-bandstop filter, smaller3dB bandwith and small size of tag, freely controlling the stopband center frequency. According to this principle, the article raises the tag designing scheme.The second part researches the change rule between stopband frequency and size parameters, proposes a stopband control method based on simulation data and proves that the two stopband frequency of double C shaped DGS can be controlled idependently. Based on the analysis above the article produces the physical model of single and double C shaped DGS and measures them by using vector network analyzer. The result shows that the actual measurement results and simulation results are similar. This article also designs a4bit chipless RFID tag based on C shaped DGS. This tag can weaken the specific frequency of the received signal and create specific frequency spectrum to identify the tag with an unique ID.The third part proposes a kind of chipless RFID tag based on loading parallel line and symmetric arc open loop DGS. This structure has the characteristic of small size and simpleness of achiving stopband. Especially this structure can control the stopband without changing the external size. In addition, this part rasearches the frequency bandwith characteristic and stopband control method of loading parallel line and symmetric arc open loop DGS, produces and measures6bit chipless RFID tag with the step frequency of0.5GHz and the relationship between the geometric size and electrical characteristics. The measured results inosculate with the simulation results. Finally, the chipless RFID tag can be equivalent to a cascade microwave network, according to the microwave network theory. On the basis of the input impedance of antenna and the simulation S-parameters of multi bandstop filter the article calculates the S parameters of the complete tag, and futheril analyzes the transmission performance of the tag.