超宽带虚拟孔径雷达非正交旁瓣抑制方法

在超宽带雷达成像中,雷达图像存在非正交旁瓣,影响图像质量。该文通过分析虚拟孔径成像的空间谱支撑区分布与点扩展函数的关系,提出一种基于虚拟子孔径的雷达图像非正交旁瓣抑制方法。该方法通过分离主瓣和旁瓣,在保持分辨率的同时有效抑制旁瓣,仿真数据处理结果验证了该文方法的有效性。     

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.     

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.     

无线通信技术在电力通信中的应用

当今全球无线通信领域热点不断出现,如何利用包括3 G、W iMAX、MMDS、LMDS、WLAN等新技术,构建坚强可靠的电力通信网,已成为电力通信一个课题。文章结合电力通信的特点,通过对无线新技术特性的分析,展望了其在电力通信系统的应用前景,目的是将电力通信专网建设成高带宽、IP化、具有强QoS保证的信息通信网络平台。     

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.     

超宽带信号在室内环境下的性能分析

在对高斯脉冲波形的时域和频域特性进行分析的基础上,采用直接序列扩频方式,进行脉幅调制产生超宽带信号.通过参考IEEE推荐的室内信道模型,重点对室内传播的链路预算进行仿真,对信号的性能进行分析和比较.经过一系列的仿真后,得出高斯四阶导数脉冲波形在实际系统中更具有实用价值的结论.     

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。