基于时域双谱估计的超宽带雷达目标特性分析

本文利用UWB雷达目标冲击响应局部分量,针对复杂目标,提出了一种时域双谱估计算法,能准确地估计出目标的散射中心分布。根据上述算法利用自行研制的冲激雷达实验系统对缩比飞机模型的实测数据作了分析,结果表明了算法的有效性。     

一种性能改进了的大张角四脊型超宽带馈源的研制

超宽带馈源在通信和射电天文等领域有着极高的应用价值。四脊喇叭作为宽带馈源的一种重要形式,存在着反射损耗性能较差,方向图随频率波动严重,照明张角难以拓展等诸多缺陷。本文基于国际上已有的研究基础,设计了一款工作于1.2~6.8 GHz的双极化大张角四脊型超宽带馈源。该设计方案对脊片部件采用了"削出倒角"、"厚度赋形"和"脊片外延"的改进措施,显著改善了馈源在低频段的反射损耗性能,同时也拓展了照明张角,使其能够更好地应用在大张角主焦照明的场合。实测结果显示出,该超宽带馈源的带宽和反射损耗性能均略优于国外样机。在边缘照明角为68°的大张角情况下,该馈源依然可以在1.2~6.8 GHz的带宽(相对带宽5.67:1)内达到低于-10 dB的反射损耗,其中在2.5~5.3 GHz内的反射损耗低于-15 dB。而且,该馈源在E面和D面的-12 dB边缘照明角随频率的波动小于20°。     

Effect and Compensation of Colored Timing Jitter in Pulsed UWB Systems

Ultra-wideband (UWB) systems impose a stringent requirement on the jitter performance of the system clock. So far, only the effect of white Gaussian timing jitter has been considered in the literature via numerical simulation. However, practical clocks commonly exhibit colored jitter. In this paper, we first investigate the bit error rate (BER) performance of a single-user binary pulse position modulation UWB system subjected to white and colored Gaussian jitter. It is shown that colored jitter degrades BER performance much more than white jitter, and the extent of degradation increases as the jitter bandwidth decreases. Motivated by this result, we then propose a new jitter compensation scheme to improve the BER performance under colored jitters with small jitter bandwidth, in which each information-bearing data symbol is coupled with a pilot symbol. The proposed scheme attempts to track first the jitter for the current pilot symbol by making use of the pulse-template correlation function. This information is then used together with the known clock jitter bandwidth and jitter root-mean-square (RMS) value to detect the current data symbol according to the maximum likelihood criterion. Simulation results show that the algorithm is effective in improving the BER performance for colored jitters with small jitter bandwidth. Lei Huang received the B.Sc. degree from Xi'an Jiaotong University, China, in 1993, the M. Sc. degree from South China University of Technology in 1996, and the Ph.D. degree from Victoria University of Technology (VUT), Australia, in 2003, all in Electrical Engineering. From 1996 to 1999, he was a Lecturer at South China University of Technology. From March 2003 to December 2005, he was with National University of Singapore as a Research Fellow. Since January 2006, he has been working in Panasonic Singapore Laboratories as an R & D Engineer. His research interests focus on physical layer aspects on wireless communication systems, especially CDMA, ultrawideband and millimeter wave communications.     

超宽带雷达系统中皮秒级脉冲源的研制

提出一种新型超宽带雷达高斯脉冲信号产生电路的设计方法,该电路利用微波三极管的开关特性和阶跃恢复二极管的阶跃特性,以及电容的充放电过程产生高斯脉冲信号,利用ADS软件对脉冲产生电路进行了仿真与分析。测量结果表明,该电路可以产生脉冲宽度400ps,重复频率1MHz,幅度4.1V的窄脉冲信号,且脉冲振铃很小,与仿真结果基本吻合,从而验证了该方法的合理性。该电路通过调节充放电电容的值实现脉冲幅度可调,当重复频率提高至10 MHz时,可得到3V～8V的幅度可调皮秒级高斯脉冲。该脉冲源能够满足超宽带雷达系统不同的应用要求。     

一种针对超宽带标准的CMOS Gm-C低通滤波器

采用TSMC 0.18µm CMOS工艺实现了一种针对超宽带标准的264MHz低通滤波器。该4阶滤波器由两个二阶滤波器级联而成,相对于传统的二阶Gm-C滤波器设计,本文提出的二阶拓扑结构十分简单有效,节约了1个跨导单元,3个共模反馈网络,2个电容。因此芯片功耗和芯片面积大大降低,其他指标并无牺牲。测试表明该滤波器增益-0.5dB,频率响应实测结果与仿真吻合良好,芯片面积为〖0.06mm〗^2,远小于同类设计,在1.8V电源电压下,电流消耗为3mA。     

一种应用于6-9GHz UWB系统的低噪声CMOS射频前端设计

本文介绍了一种应用于6-9 GHz超宽带系统的全集成差分CMOS射频前端电路设计。在该前端电路中应用了一种电阻负反馈形式的低噪声放大器和IQ两路合并结构的增益可变的折叠式正交混频器。芯片通过TSMC 0.13µm RF CMOS工艺流片,含ESD保护电路。经测试得该前端电路大电压增益为23~26dB,小电压增益为16~19dB;大增益下前端电路平均噪声系数为3.3-4.6dB,小增益下的带内输入三阶交调量(IIP3)为-12.6dBm。在1.2V电压下,消耗的总电流约为17mA。     

Adapting the Ranging Algorithm to the Positioning Technique in UWB Sensor Networks

Ultra-Wideband (UWB) is an emerging technology for short-range wireless communications. Due to the high bandwidth of UWB signals, accurate ranging and positioning is possible, which is one of many reasons why UWB is a candidate physical layer for another emerging research area, that of wireless sensor networks (WSNs). In this work, we argue that the ranging algorithm design should be made with the characteristics of the positioning algorithm in mind. In considering ranging and positioning in parallel, we are able to construct a range estimator that is tailored to the positioning algorithm, thereby achieving robustness to non-line-of-sight (NLOS) effects, reasonable overall complexity, and good performance in terms of positioning error. The analysis and simulations in this work are based on the channel models adopted by the IEEE 802.15.4a working group, and highlight the benefits and drawbacks of the proposed approach.     

Novel analysis and optimization of gm-boosted common-gate UWB LNA

This paper focuses on the design optimization of g_m-boosted common gate (CG) CMOS low-noise amplifier (LNA) for ultra-wideband (UWB) wireless technology. In this regard, a detailed novel analysis of the UWB g_m-boosted CG amplifier topology is presented, which includes the finite g_ds (=1/r_eds) effects. For UWB systems, signal-to-noise ratio (SNR) can be defined as the matched filter bound (MFB). Using this definition, the noise performance of the UWB CG LNA in the presence of the g_m-boosting gain and the input noise-matching network are analyzed. It is found that the optimal noise factor of the UWB LNA collapses to the published narrowband g_m-boosted CG LNA noise factor when an assumption of narrowband is applied. It is also proved that the noise performance of the g_m-boosted UWB CG LNA is independent of the bandwidth of the input UWB signal. A new technique is presented for the design of optimal noise-matching network using passive components at the input of the UWB CG LNA. In this regard, role of the g_m-boosting stage and its effect on the SNR and the gain of the overall system are analyzed, and, in addition, its non-idealities are simulated in detail.     

时域分析钢筋混凝土砖墙对电磁脉冲短径传播的影响

用时域有限差分法分析了钢筋混凝土砖墙对电磁脉冲传播的影响。考虑到天线对时域脉冲的滤波效应，分析的传播脉冲信号是从一个宽带圆锥柱形天线上数值生成的。计算结果给出了钢筋混凝土砖墙对脉冲信号传播的影响，包括辐射天线产生的脉冲波形的畸变效应、脉冲穿透钢筋混凝土砖墙时的场型分布、墙面对入射脉冲峰值的反射效应以及反射和透射脉冲的波形。     

早期乳腺肿瘤的超宽带微波成像

通过采用时域有限差分方法探讨了一种收发天线分离的早期乳腺癌超宽带微波成像检测方案.在收发共用的超宽带天线设计中要求天线的终端反射不超过-120dB,而采用收发天线分离方案则避免了这一苛刻要求.采用共焦成像算法给出的成像结果表明,该方案亦可探测直径10mm以下的早期乳腺肿瘤.