Saw Radio Frequency Identification-based Encoding

The encoding theory, data structure and some performance parameters of SAW Radio-Frequency Identification (RFID) tags are studied. The purpose is to look for a coding method with large data capacity of tags.The purpose of identification is to read out the coding information of SAW tags, so the study for coding of SAW tags is the basis, and also is a key technology of RFID. The work principle of SAW RFID system and physical structure are introduced simply. The mathematic model of pulse response of SAW tags is deduced from the pulse response model of IDT. The information of amplitude, phase and time position included in the pulse response of SAW tags are studied. The coding methods of ON/OFF coding, 2PSK coding and pulse position coding are deduced by using the reflected electrode's physical structure of SAW tags to modulate those parameters of pulse reponse of SAW tags. The theory and data structure of those encoding methods are studied in this paper, moreover, the performance of encoding methods is stuied by a set of parameters. On the base of studies of these three coding methods, a pulse position coding based on stepped-frequency interrogation-pulse-stepped-frequency pulse position coding-was presented and studied. First, the theory of stepped frequency SAW RFID system and performance parameters, ambiguity function and wave parameters design of stepped frequency signal are studied. Second, the theory and data structure are studied emphatically, three group parameters of stepped-frequency pulse position coding system are selected and the performance parameters are analyzed. At last, the good performance such as the bit density, D, the figure of merit, H and the detected distance are showed by comparing these coding methods.In conclusion,three following parts was including:1. The theory of SAW RFID system is studied, and the ON/OFF coding, 2PSK coding and pulse position coding are studied.2. The ambiguity function, performance parameters and wave design principle are discussed. A set of parameters of stepped-frequency signal were designed based on the application environment of SAW RFID system. 3. The encoding theory, data structure and performance parameters of stepped frequency pulse position coding were presented and studied. At last, these coding methods were compared in this paper.