【作者】 张桂英；

【导师】 戴宇杰；

【作者基本信息】 南开大学 ， 微电子学与固体电子学， 2013， 博士

【摘要】 随着射频识别、信息传感等信息通信技术的发展,信息网络将向无所不在的泛在网络方向演进,“泛在”将成为信息社会的重要特征。泛在网络作为未来信息社会的重要载体和基础设施,已经得到国际普遍范围的重视,各国相继将泛在网络建设提升到国家信息化战略高度。论文在对泛在网络进行了相关介绍的基础之上,提出了一种适用于构建泛在网络的终端系统：半超宽带超高频射频识别(SUUR)系统。并根据从系统分析到模块电路设计再到整体电路仿真与验证的方向对该系统进行了研究设计。首先,对该系统的组成及其基本工作原理进行了论述,并对相关协议标准进行了分析；接着,对SUUR无源电子标签芯片的整体结构进行了分析与设计,对标签芯片的整体性能指标进行了规划；然后,重点研究了SUUR无源电子标签芯片射频模拟前端电路的设计,包括自适应阻抗匹配电路、IR-UWB脉冲发射电路和RF接收电路等。为实现最大功率传输,通常需要设计一个阻抗匹配网络来实现电子标签芯片阻抗和接收天线阻抗之间的共轭匹配。由于在设计中通过仿真得到的天线及芯片的阻抗与实际值总是存在一定的偏差,因此在实际应用中,应采用网络分析仪对芯片阻抗进行测试,然后根据测试结果,对天线设计进行多次修正,调整天线阻抗,最终达到最佳能量传输。事实上,芯片阻抗的实际值也会随着输入功率的变化而产生波动,因此在使用固定的阻抗匹配网络情况下,即使通过反复测试、调试后设计的天线,在实际工作过程中也很难始终保证和芯片处在最佳匹配状态,从而影响标签的阅读距离及其整体性能,甚至有可能出现“死区”现象,不能正常工作。因此,为使电子标签天线设计简单化(在可调电容调谐范围足够大时可直接选用阻抗为50Ω通用天线)、提高标签的阅读距离并消除“死区”现象,本论文设计了一种自适应阻抗匹配系统来实现天线阻抗与芯片阻抗之间的实时、自动匹配,从而实现标签的最佳传输性能。该匹配网络包含2个独立的环路：第1个环路通过对并联LC调谐网络的控制实现对芯片阻抗实部的实时检测与自动校正,而第2个环路通过对串联LC调谐网络的控制实现对芯片阻抗虚部的实时检测与自动校正。在这2个环路中,调谐元件采用的都是与标准CMOS工艺兼容的MOS可变电容,以实现单片集成和连续调节。在第1个环路中,除了检测阻抗的实部信息外,还检测虚部的正负特性作为第2个控制准则来确保环路的稳定性。另外,本文还对该匹配系统的关键电路进行了设计,并在915MHz频率下对不同的芯片阻抗进行了仿真验证,结果表明：对于不同的芯片阻抗,都能快速地校正到目标阻抗。另外,对电容的调谐范围及调谐网络的非理想特性进行了分析,调谐网络的插入损耗低于1.5dB,系统增益可高达2.7dB。UWB一个重要的设计初衷就是希望能够和已有的窄带通信设备共享频谱资源。为确保UWB通信系统不干扰其他窄带系统的正常工作,一个有效的方式就是限制其发射功率谱密度,但这还不足以完全解决UWB信号对其它无线电信号的干扰问题。本论文将相互之间具有延迟时间△t的两个n阶高斯脉冲相加,得到的组合脉冲也满足IR-UWB泳冲的特性,且其功率谱密度是n阶高斯脉冲的功率谱密度与余弦函数的乘积,因此在某些特定频率处将具有陷波(功率谱密度为零),陷波频率的数值与延迟时间成反比,且对于某一个确定的延迟时间,在UWB频带内可存在一个或多个陷波频率,从而可以灵活实现对现有某一个或多个窄带通信系统干扰的抑制。基于Chartered0.18μm2P4M EEPROM工艺,采用低功耗设计技术对SUUR标签芯片射频模拟前端电路进行了设计,并对其进行了整体仿真验证。结果表明,该SUUR标签芯片工作中心频率为915MHz,其工作距离大于10m,很好的满足了设计指标的要求。更多还原

【Abstract】 With the development of the information and communication technology, information network will develop to ubiquitous network. Ubiquitousness will become an important feature of the information society. As an important carrier and infrastructure in the future information society, ubiquitous network has attracted the international widespread attention, and many countries have promoted the ubiquitous network construction to national informatization strategy.In this thesis, a terminal system named semi-UWB Ultra-high frequency radio frequency identification (SUUR) is presented based on the introduction of ubiquitous network. The research and design is organized as follow:from the system analysis to cell block circuits design and finally to the whole RF analog front-end circuit simulation and verification. Firstly, the system structure and the operating principle are discussed, and the relevant protocols are analyzed. Secondly, the system architecture of the passive SUUR tag IC is analyzed and designed. The specifications of the SUUR tag IC are presented. Furthermore, the system architectures of the radio frequency analog front end (RF AFE) for the passive SUUR tag are studied and designed with low-power design techniques. The RF AFE circuit includes adaptive impedance matching network, RF receiver and IR-UWB pulse generator, and so on.To realize power transfer maximization, an impedance matching network which is used to transform the tag microchip impedance to the complex conjugate of the antenna impedance is usually designed. Usually, there is a certain deviation between the real and simulation values of chip impedance, in practical applications, a network analyzer should be used to test the chip impedance and according to the test results, adjust the antenna impedance again and again, and ultimately achieve the best energy transfer. Actually, the impedance of the microchip may also vary with the received power on the chip. Therefore, if a fixed impedance matching network is used, serious mismatching may be still exist and thus create a "dead-zone" where the tag is non-responsive even the tag is deployed in the reading range (especially closed to the reader). To simplify the design of the tag antenna (50ohms can be used if the capacitance tuning range is large enough), to improve the reading area, and to eliminate "dead zones" phenomenon, in this thesis, an adaptive impedance matching network is designed to realize real-time and automatic impedance matching between the tag and antenna thus realize the maximum power transfer and the best link quality. The adaptive impedance matching network consists of two independent loops. The first loop realizes real-time measurement and automatic correction of resistance by controlling a parallel LC tuning network, whereas the second loop achieves automatic reactance compensation by controlling a series LC tuning network. In both loops, MOS varactors which are compatible with standard CMOS processing were applied as tunable elements to realize monolithic and sequential tuning. For the first loop, besides the intermediate resistance, the sign of the intermediate reactance was also detected as the second control criterion to enforce operation into a stable region. In addition, the key circuits of the matching system are designed. For different chip impedance, the adaptive impedance matching system was simulated at frequency of915MHz, and the results showed that:all the chips impedance can be quickly corrected to the target impedance. In addition, the analysis are carried out on the non-ideal characteristics of the tuning network and the tuning range of capacitance, it is indicated that the insertion loss is less than1.5dB and the system gain can be as high as2.7dB.One of the important design intentions of UWB is sharing spectrum with exiting narrow band communication systems. In order to ensure that the UWB will not interfere the narrowband communication systems, an effective way is to limit the transmit power spectral density. However, it is not enough to completely solve this problem. In this thesis, a composite pulse was generated by combining two n-th derivative Gaussian pulses with delay time of At. This pulse satisfies the characteristic of the IR-UWB pulse, and its power spectral density is the product of the power spectral density of n-th derivative Gaussian pulse with cosine function. So notch frequencies will be generated at some certain frequencies and inversely proportional to the delay time. In addition, there are one or more notch frequencies in the UWB band for a certain delay time. Therefore, it is flexible to suppress interferences on one or more narrow-band communication systems.An overall design and simulation are conducted for the RF AFE of passive SUUR tag IC based Chartered0.18μm two-poly four-metal (2P4M) CMOS process with Schottky diodes and EEPROM. The results show that the chip’s reading range is more than10m at the915MHz ISM band. The tag IC meets the requirements of the design specifications.更多还原