【作者】 范志广；

【导师】 冉立新； 陈抗生；

【作者基本信息】 浙江大学 ， 电子科学与技术， 2007， 博士

【摘要】 本学位论文的工作在超高频射频识别(UHF RFID)系统的理论研究和设计实践领域进行，包括了长距离无源后向散射UHF RFID阅读器射频前端的研制、UWB(超宽带)RFID系统源脉冲波形的优化设计、UHF RFID阅读器小型化天线的研制和UHF RFID标签天线的优化设计四个方面的研究内容。本论文为研制长距离UHF频段无源后向散射RFID阅读器射频前端提供了数学公式化理论模型和工程设计方案，填补了该领域的研究空白。论文研究了阅读器射频前端的工作原理并进行了详细的系统信号描述和分析，给出了整机结构及其射频前端的设计细节。通过计算标签的时间平均吸收功率和接收机解调输出信号的信噪比，论文给出了阅读器工作距离的数学公式模型，并概括了如何增加阅读距离的一系列关键设计建议。论文也给出了915 MHz和2.45 GHz两个频段阅读器射频前端的详细硬件设计和工程实现方案，对它们进行了测试评估，获得工作距离为11.8米的阅读器原型机，其性能达到了国际上一流阅读器设备的水平。测试结果和理论计算结果也显示了很好的一致性，验证了论文所给出的数学公式模型和设计方法的有效性。本论文为UWB RFID系统的源脉冲波形优化提供了创新性的数学公式化理论模型和设计实现方法。论文研究了基于延迟反射脉冲序列无源标签的UWB RFID系统的基本工作原理并进行了详细的信号描述和分析，通过建立基于接收脉冲“有效能量”概念的源脉冲波形函数的泛函和使用变分计算泛函极值，得到了相关于第二类齐次Fredholm线性积分方程特征函数的源脉冲波形最优解数学公式模型，并开发了一套有效的数值求解算法。论文也展示了一个UWB脉冲传输系统的设计例子，给出了优化所得的源脉冲信号波形，并比较了它和一些常见脉冲的传输性能差异，验证了所给出的优化模型和设计方法的有效性。基于论文所给出的数学模型，在设计UWB RFID系统时，通过优化阅读器的查询脉冲波形，就能增加阅读距离，获得最佳的系统性能。本论文研制了工作在2.45 GHz频段的小型化具有方向性增益的平面印制偶极子形式的UHF RFID阅读器天线。论文设计了新型的V形地平面反射结构，增加了天线的阻抗带宽和改善了它的辐射方向性，并通过电磁仿真优化得到了尺寸仅为51mm×40mm×1.6mm的小型化阅读器天线。测量结果表明，其百分比阻抗带宽大于33％，峰值天线增益超过了2dBi，后向辐射抑制超过7dB，性能优于无V形反射结构的传统天线。本论文开发了工作在2.45GHz频段的小型化平面印制偶极子形式的UHFRFID标签天线。论文设计了新型的阻抗变换器结构以对短偶极子进行电阻提升和感性补偿，有效地小型化了天线设计，并通过电磁仿真优化得到了尺寸仅为33.55mm×8.54mm×0.50mm的小型化标签天线。所设计天线实现了与标签芯片的良好共轭阻抗匹配，其方向图具有理想的全向辐射特性，峰值增益也达到-0.2dBi，满足了小型化标签天线的设计要求。更多还原

【Abstract】 This dissertation focuses on theoretical investigations and design practices of ultra-high-frequency radio frequency identification (UHF RFID) systems, which are carried out in four research areas as follows: a) Design of the RF front-ends of long range passive backscatter UHF RFID readers; b) Source pulse waveforms optimizations for Ultra-wideband (UWB) RFID systems; c) Miniaturized antenna designs for UHF RFID readers; d) Design optimizations for UHF RFID tag antennas.This dissertation provides mathematically formulated theoretical models and practical engineering designs for developing the RF front-ends of UHF-band long range passive backscatter RFID readers, which fill the gap in the relevant research area. The operational principles of the reader’s RF front-end are investigated and the signals in the system are described and analyzed in detail. The reader’s structure is proposed and particularly the design details of its RF front-end are presented. Through evaluating the time-averaged absorption power of the tag and the demodulation output signal-noise-ratio of the receiver, the mathematical models of the read range are figured out. Based on the models, several key design suggestions are concluded to improve the performance of read range. This dissertation also presents the detailed hardware implementations and engineering designs for the RF front-ends of two readers, of which one works at 915 MHz and the other one at 2.45 GHz. The prototype readers are manufactured and measured, which achieve the read range of 11.8 meters and are comparable to the first-class readers in the international markets. The measurement results also show good agreement with the calculated ones, which validate the proposed mathematical models and design methods well.This dissertation creatively provides mathematically formulated theoretical models and design methods for optimizing the source pulse waveforms of UWB RFID systems. The basic operational principles of UWB RFID systems that are based on the delay-reflection-pulse-sequence passive tags are investigated and itssignals are described and analyzed in detail. Through establishing the functional of the source pulse which is based on the concept of "usable energy" in the received pulse and then extremizing the functional by means of the calculus of variations, the mathematical models of the optimized source pulse waveforms are shown to be associated with the eigenfunctions of a homogeneous Fredholm linear integral equation of the second kind. An efficient algorithm is developed for numerically solving the integral equation models. A design example of UWB pulse transmission system is also demonstrated and the optimized source pulse waveforms are figured out. Specially, the transmission performance of the optimized pulse is compared with that of several common pulse waveforms, which validates the proposed optimization models and design methods well. Based on the proposed mathematical model, through optimizing the interrogating pulse waveforms of the reader, its read range can be maximized to efficiently improve the overall performance of UWB RFID systems.This dissertation develops a 2.45 GHz miniaturized planar printed-dipole-type UHF RFID reader antenna having necessary directive gain. The novel V-shaped ground plane reflection structure is proposed, which increases the antenna’s impedance bandwidth and improve its radiation directivity. The antenna’s dimensions are optimized by means of electromagnetic simulation and the finalized antenna’s size is only 51 mm x 40 mm x 1.6 mm. The measurement results show that the antenna’s percent impedance bandwidth is 33%, the peak antenna gain is more than 2 dBi, and the backward radiation suppression is beyond 7 dB, which all demonstrate better performance than the traditional antenna without such a V-shaped reflection structure.This dissertation develops a 2.45 GHz miniaturized planar printed-dipole-type UHF RFID tag antenna. The novel impedance transformer is proposed to boost the resistance of the short dipole and simultaneously compensate its reactance inductively, which contributes to miniaturizing the tag antenna efficiently. The antenna’s dimensions are optimized by means of electromagnetic simulation and thefinalized antenna’s size is only 33.55 mm × 8.54 mm × 0.50 mm. The antenna achieves good conjugated-impedance matching with its terminated microchip, its radiation pattern has the ideal omni-directionality and the peak antenna gain reaches -0.2 dBi, which all meet the design requirements for the miniaturized tag antennas well.更多还原