Research On Reader Chip Design Of RFID And Its Communication Algorithm

RFID is a non-contact automatic identification technology relying on radio frequency waves to identify the objects automatically. RFID system consists of readers, tags and data processing system. As the core of the system, the demand of the reader grows rapidly as RFID technology popularizes. High-performance discrete devices and modules designed reader made the cost higher, while the single-chip reader can reduce the cost, power consumption and size. So high-performance, low-cost reader chip design is important.With the expansion of RFID applications, readers are required to quickly identify hundreds of target. Anti-collision algorithm is the key technology for multi target recognition which can effectively solve the problem of collisions between multi tags. Meanwhile, wireless communications between readers and tags bring out the security risks, which require security authentication protocols and encryption algorithms. Anti-collision algorithm and encryption algorithm are the main algorithms in the RFID communication system, and its research is of great significance.Reader cost, multi-target recognition rate, RFID system security has restrained RFID development. This dissertation is focusing on reader chip design, anti-collision algorithm, security authentication protocols and encryption algorithms.Firstly, the antenna model is deduced from the theoretical foundation and the operation of both near field and far field region are explained. On this basis, the energy and signal transmission model of the RFID system is established. The analysis of inductive coupling model and the load modulation model in the near-field mode provides a theoretical guide for the circuit design.According to the protocol and the functional requirements, RF front-end architecture the high frequency reader is established. The whole chip is divided into demodulation circuit, band pass filter, variable gain amplifier, and pulse shaping circuit. A low-power, low-cost sampling-based switched capacitor circuit is proposed according to the characteristics of load modulation signal and the comparison and analysis of the traditional demodulation circuit. The signal is divided into I, Q channel to remove the carrier signal efficiently. In order to effectively filter the noise, band pass filter is used after the sampling circuit and variable gain amplifiers. Pulse shaping circuit utilizes the Schmitt trigger structure to increase the output drive capability. The circuit is simulated on SMIC 0.35μm embedded EEPROM technology.To solve the collision problem in reading tags, a dynamic frame ALOHA algorithm based on binary splitting and Bayesian estimation is proposed. The algorithm uses the optimal group, the optimum frame length adjustment and binary splitting strategy in collision slots to improve the throughput of the system. Tags are partitioned into groups by "bit mask" to avoid collision generated by excessive number of tags. Bayesian estimation takes the advantage of the evidence in previous frames as the priori information of the current frame which leads to the precise estimation of the tag number and rational frame length adjustment. Binary splitting strategy is used in collision slots which is divided into sub-slots, tags then randomly communicate with the reader. This strategy can exceed the throughput limit of the traditional ALOHA algorithm.Based on the requirements of pseudo-random number in RFID security authentication protocol, the pseudo-random number generator of random parameter is introduced, which increase the unpredictability of pseudo-random number. Then a security authentication protocol based on this pseudo-random number generator of is proposed. The framework of the protocol, the realization of one-time password, and a mathematical method to achieve the low power requirement is introduced, which provide a new solution to the contradiction between improve the security certification level and reduce the complexity and the power consumption.In conclusion, this dissertation provides a complete circuit design for the RFID reader chip, and offers important innovative ideas for communication algorithm between the reader and tag.