Research And Design Of Radio Frequency Identification Reader

The research and development on UHF RPID reader and tag are driven by the requirements in application of UHF RFID systems in recent years. Simultaneously, CMOS RFIC developed very fast and it is possible to integrate a wireless transceiver into a chip via CMOS process.Theoretical analysis about UHF RFID system and reader is described in this thesis, and most of the efforts are distributed on the key technologies of RFID system.At first, theories on propagation of eltromagnetic wave, antenna model, and antenna link, the most pivotal parts in wireless communications system, are introduced in this thesis. Based on ground two-ray propagation model, an electromagnetic wave propagation model is developed. As is pointed out by this model, tag could not setup communication link with reader successfully when it is located at somewhere due to not enough received power induced by channel fading.Secondly, a power distribution model of tag is researched in the system link analysis. It concludes that the maximum operation range is determined by the power consumption of tag and the sensitivity of reader. A comparison of the tag reflection power is made between the calculation and measurement. The similar results of calculation and measurement proved that calculation is correct.Thirdly, the architecture of reader front end is determined based on the analysis of RFID protocols and wireless frequency regulations. Both of the transmitter and the receiver are on direct conversion architectures with IQ branches. The architecture is flexible for multi-modulation types, and upgradeable. The out band spurious spectrum is limited by raised cosine filter in transmitter, and the shadow effect can be removed by combining the signal power of two branches in receiver.Fourthly, most of the effects in the front end of reader are analyzed systemically, and especially focused on spectrum suppression for transmitter, and input noise and signal, DC offset cancellation, and system parameters calculation for receiver. Base on theoretical analysis, a system model of RFID is developed. Theories are verified by system simulation.Finally, system parameters are optimized for CMOS chip design. That is to say, choose a proper transmitting power, the operation distance will tend to reach a relative maximum, under the limitation of reader sensitivity. Part of the building blocks are designed and implemented.