超高频射频识别读写器芯片的多噪声建模与优化方法研究

Due to the backscatter communication mechanism of the reader supplying energy to passive tags, the ultra-high-frequency radio frequency identification reader integrated chip's sensitivity is limited by the amplitude of continuous carrier leakage and the correlated amplitude and phase noise performance. Using the reader transceiver noise transfer law as starting point and the precise sensitivity test platform as basis, this research is intended to research the noise contribution physics mechanisms of various modules, including the receiver itself amplitude noise, phase noise of the local oscillator, amplitude noise of the transmitter power amplifier, amplitude noise of the transmitter baseband filter, phase-amplitude conversion noise of the transmitter mixer, establish the overall reader receiver noise figure mathematical model and the SpectreRF-based system simulation model. The study aims to dig the essential noise issues behind phenomenon of carrier leakage deteriorating the reader receiver sensitivity and establishes an operable and reliable noise modeling method using modern integrated circuit noise theory and computer processing technology. The study seeks the circuit optimization methods and structure optimization methods and verifies them in a reader chip design instance with the significantly improved sensitivity performance of -90dBm at 10dBm continuous carrier leakage. The research is expected to significantly improve realibility performance of ultra-high-frequency radio frequency identification system and double the recognition distance or more with same reader transmit power and tag sensitivity.

超高频射频识别读写器的灵敏度受限于读写器读取无源标签过程供给标签能量引起的载波泄漏电平及其噪声属性，这已成为当前读写器芯片性能提升的瓶颈。本申请拟以读写器收发机噪声传递规律为切入点，精确灵敏度测试平台为手段，研究多噪声源包括接收机自身AM噪声、本振PM相位噪声、发射机基带滤波器AM噪声、功放AM噪声和混频器PM-AM转换噪声等影响接收机灵敏度的物理机制，建立接收机噪声系数数学模型和系统仿真模型。研究旨在挖掘载波泄漏恶化读写器接收灵敏度问题背后的噪声本质，依据现代集成电路噪声理论、计算机处理技术，提出一种可操作性强、可靠性好的噪声建模方法。以上述研究为基础，寻求接收机噪声系数的系统结构与电路设计优化方法，设计一款灵敏度性能显著提升的读写器芯片样品，10dBm载波泄漏时灵敏度达到－90dBm。研究成果有望显著提高射频识别系统可靠性，在同等读写器发射功率与标签灵敏度时，将识别距离扩展一倍以上。

本课题搭建了具有控制载波泄漏幅度与相位能力的读写器－标签灵敏度测试系统平台，通过测试结果得到了RX端载波泄漏信号与接收路径LO的相关性对接收机灵敏度的影响，即在载波泄漏一定时，当RX接收到的载波泄漏与从发射机回引的LO信号具有良好的相关性，即相移相同时，由于载波泄漏引起的灵敏度恶化问题不明显。如能将RX载波泄漏信号与LO信号做到完全相关，则可获得接收机最佳接收灵敏度。. 基于实验结果，建立了包括接收机相位噪声性能、发射机输出噪声基底、接收机载波泄漏功率、载波泄漏消除电路噪声性能及载波泄漏抵消能力在内的接收机椭圆噪声系数数学模型，制定了“多角度噪声优化+载波泄漏消除”两种方法并行的高灵敏度读写器芯片设计策略。. 为解决UHF RFID读写器射频前端的10dBm级别载波泄漏问题，提出了一种新型的闭环反馈去除载波泄漏的方法，有效提高系统的灵敏度。. 基于以上的数学模型和系统分析，设计完成了一款灵敏度高度优化的射频识别读写器芯片，该芯片采用0.18µm SiGe BiCMOS工艺实现，测试结果显示：误码率为0.1%的条件下，监听模式时接收机的灵敏度为-91.2dBm，读写模式时（存在10dBm载波泄漏）接收机的灵敏度为-85.4dBm。阅读器可在6米的距离稳定识别标签。. 本课题的研究成果为超高频射频识别读写器的高灵敏度优化设计提供了有用的理论依据和较准确的模型，所设计和优化的芯片也可作为企业产品的原型。