Research Of Chipless RFID System Based On Backscatter Theory

Radio Frequency Identification (RFID) is a non-contact automatic identification technology, identifying specific target and Reading the specific information contained in the target by transmitting electromagnetic signals. Compared to bar code technology, RFID technology has characteristics of longer reading distance, penetration, Larger information, interference and so on. Currently, most RFID tags consist of active or semi-active devices, whose high production costs hinder the promotion and application of RFID technology seriously. So, chipless RFID technology with lower production cost widespread attention by scholars. This paper applied the theory of backscatter characteristics, focused on Chipless RFID tags and readers systems based on this feature, and completed the work as the following aspects.Firstly, this paper elaborated RFID system components and how they work, and analysis of the basic parameters and time-domain scattering model of single port antenna.Secondly, this paper focused on the model of tags based on the time domain tag backscatter principle and design the tag. An ultra-wideband antenna is used as the tag antenna, and performance parameters of the antenna are simulated which to determine the suitability. Performing transient simulation of the tag by electromagnetic simulation software CST, Analyzing the impact of labeling scattered signal by length of transmission lines, intensity of transmission lines, and loads. Two chipless RFID tags are presented:single-port load tag And dual-port loads tag.Single-port load tag is encoded according to Influence on scattering signal by the length of transmission line. Dual-port loads tag is encoded according to Influence on scattering signal by the loads.Thirdly, RFID reader system was designed according to chipless RFID tag based on the principle of backscatter. The generation and reception of ultra-wideband signal is the important and difficult to the system. The transmitter section generate ultra-wideband pulse as the reader signal based on avalanche principle. In the receiver section, sampling gate circuit, the sampling pulse generating circuit, the sampling pulse drive circuit, a variable delay circuit stepper were designed. The transmitter and receiver were simulated by software ADS, The results show that backscattered signal get a well analysis and recognition.