室内环境下超宽带信号透射特性仿真与分析

时域射线跟踪技术是研究室内环境下超宽带信号透射特性的有效方法。本文利用时域射线跟踪方法研究了超宽带信号在室内环境的透射特性。然后对典型室内环境仿真，分析透射对超宽带信号功率延迟分布的影响。     

超宽带信号在室内不同环境下传播特性的研究

详细研究了室内不同环境下超宽带信号传播的特性,通过时域射线跟踪法对两种不同室内环境的场强信号进行预测,仿真表明接收总功率,均方根时延扩展,相干带宽以及多径到达角均和环境有密切的关系。     

复杂室内环境超宽带信号信道模型及仿真结果分析

一种应用于复杂室内环境的超宽带信号信道仿真模型,用以分析和描述超宽带信号经室内透射、反射和绕射传播后的时域电场强度.在已有的由射线法结合反射、绕射系数的仿真模型基础上,增加了对墙壁透射的分析,比较了不同墙壁参数对透射系数的影响.结果表明,在弱损耗情况下,存在较强的透射信号,因而包含透射的仿真模型具有实际意义.     

UWB信号波形失真研究

本文基于射线跟踪法在时域研究超宽带系统的传播特性。经过MATLAB的仿真实现,在发射端和接收端比较电场波形,研究环境因素对波形失真的影响,包括电场的极化类型、墙壁的电磁参数、入射射线的入射角大小等。     

MB-OFDM-UWB系统基于时域扩展的盲频率跟踪算法

对多频带正交频分复用超宽带系统同步技术进行研究,提出一种基于时域扩展技术（TDS）的盲载波频偏（CFO）跟踪算法。利用数据符号与其时域扩展符号的特殊映射关系,在时域和频域分别推导出残余载波频偏的盲估计公式,并构建相应的时频跟踪环路。仿真结果表明,该盲算法具有比导频辅助法更优的跟踪性能。10dB信噪比下,基于TDS进行时频跟踪的残余CFO均方根误差均达到2×10?4,系统误比特率可达10?6数量级。     

SBR/Image时域射线跟踪法对UWB信号的仿真

超宽带（UWB）通信系统因为其良好的抗多径性,及比较高的传输速率引起越来越多的科研人员的研究兴趣。射线跟踪是一种被广泛应用于移动通信和个人通信环境中预测无线电波传播特性的技术,它同样适用于研究室内UWB无线信道的特征,能够提供精确度较高的预测结果。本文采用SBR/Image这种射线跟踪技术对UWB信号的传播特性进行了研究,利用MATLAB语言实现了上述算法,并结合相关文献对特定的室内视距环境进行仿真及数据分析,计算结果与文献结果吻合良好,表明本文方法是正确有效的。     

跳时脉位调制超宽带信号的功率谱密度分析

通过对时域信号的自相关时间均值函数做傅氏变换,推导出定周期跳时脉位调制超宽带脉冲序列的功率谱密度公式,形式更加简明;并分别在时域和频域进行仿真、分析,比较两种仿真结果,同时分析了跳时码周期和时延常数等参数对谱密度结构的影响,验证了推导结果与时域仿真的一致性。     

一种超宽带天线的辐射特性分析

超宽带系统一般采用超宽带短脉冲信号,因而其天线系统也必须为宽带的。给出了一种新型的超宽带天线,该天线为置于镜像面上且具有离散指数电阻加载的单偶极子。通过时域有限差分法分析了电阻加载对天线辐射性能和波形的影响。计算结果表明,通过选择一定的电阻加载形式,可以消除由于天线未端阻抗不匹配而引起的二次反射,使天线具有较好的辐射波形和一定的带宽,从而能够满足实际超宽带系统的需要。     

基于RANPLAN iBuildNet的射线跟踪算法原理及实现

介绍无线信号在自由空间传播的一种确定性传播模型、射线跟踪传播模型的原理以及一种改进的射线跟踪模型：随后介绍RANPLAN公司iBuildNet软件中集成的射线跟踪传播模型模块的实现算法;最后通过一个具体的实验场景,验证射线跟踪传播模型进行无线信号预测的准确性。     

脉冲超宽带测控信号时延精密跟踪方法

脉冲超宽带测控新体制可有效提高测控系统的安全性能,且具有潜在的高精度测距能力.为了实现其高精度测距功能,提出了一种基于延迟锁定环路的脉冲超宽带测控信号时延精密跟踪方法.该方法在传统伪码跟踪环的基础上进行改进,利用基于非相干积分的非线性反馈环路对接收信号的脉冲相位进行精密跟踪.理论分析和仿真结果表明,该延迟锁定环路可以完成对脉冲超宽带测控信号的时延精密跟踪.与直扩测控信号相比,在相同条件下,脉冲超宽带测控信号的时延跟踪相对误差更大,但由于脉冲宽度很窄,在一定载噪比条件下,其测量精度仍可达厘米量级甚至更高.     

Novel method of UWB antenna optimization for specified input signal forms by means of genetic algorithm

A novel optimization procedure for the design of antennas for ultrawideband (UWB) wireless communication systems is presented. The optimization is based on the time-domain characteristics of the antenna. The optimization procedure was applied to a simplified version of the volcano smoke antenna proposed by Kraus. However, any other type of UWB antenna can be treated with the same technique. Our optimization procedure aims at finding an antenna not only with low VSWR but also a low-dispersion one which will ensure high correlation between the time-domain transmitting antenna input signal and the receiving antenna output signal. In pulse communications systems, usually an input signal form suited to a particular purpose is used. Hence, we strive to design the best antenna for a given input signal form. The optimization technique adopted here makes use of genetic algorithm (GA) search concepts. The electromagnetic analysis of the antenna is done by means of a finite-difference time-domain method using the commercially available CST Microwave Studio software.     

UWB信号波形传播特性研究

研究超宽带（UWB，ultra-wideband）的传播特性，是UWB信道理论研究的核心内容。利用Fourier变换对各种超宽带（UWB）脉冲波形的室内反射、透射和绕射进行了研究，并提出了一种新的n阶修正Bessel函数的渐近公式，仿真结果和时域的精确结果对比，一致性吻合较好。     

一种小型平面超宽带天线的设计与研究

提出了一种新颖的小型平面超宽带(UWB)天线.该天线由微带槽天线的基本结构变形而来,为获得超宽带频率特性,设计时馈电微带线采用了渐变结构的叉形调谐支节,金属底板的开槽设计成对称多边形.首先通过数值计算来获得最佳的天线几何尺寸,并制作了实际的样品.对天线的反射特性、方向图以及增益都进行了测试,然后利用时域有限差分(FDTD)方法计算了天线收发脉冲信号的保真度.研究结果显示该天线具有良好的超宽带特性.     

On the Development of an Integrated CMOS-Based UWB Tunable-Pulse Transmit Module

A novel low-cost low-power fully integrated tunable transmit module composed of a tunable CMOS monocycle pulse generator and compact uniplanar antenna was designed, built, and tested for ultra-wideband (UWB) impulse systems. The CMOS tunable pulse generator integrates a tuning delay circuit, square-wave generator, impulse-forming circuit, and pulse-shaping circuit in a single chip using a standard low-cost 0.25-$muhbox m$CMOS process. It can generate a monocycle pulse and Gaussian-type impulse (without the pulse-shaping circuitry) signals with tunable pulse duration. A compact uniplanar UWB antenna was also developed and integrated directly with the CMOS pulse generator chip to form the complete integrated tunable UWB transmit module. Measured results show that the CMOS tunable pulse generator can produce a 0.3–0.6-V peak-to-peak monocycle pulse with 140–350-ps tunable pulse duration and a 0.5–1.3-V peak-to-peak impulse signal with 100–300-ps tunable pulse-duration, and the uniplanar antenna has less than a 18-dB return loss and is suitable for transmitting/receiving UWB time-domain impulse signals covering the entire UWB bandwidth of 3.1–10.6 GHz. Good agreement between measured and calculated performance is also achieved. The UWB transmit module was experimentally characterized and its performance is verified. This UWB module finds applications in various time-domain UWB systems including wireless communications and radar.     

Compressed sensing based deconvolution algorithm for time-domain UWB channel modeling

Extracting the parameters of the multipath with high accuracy can be achieved by using high-resolution algorithm for time-domain ultra wideband (UWB) channel modeling.The CLEAN algorithm has been used ...     

Measurement and Analysis of Ultra-Wideband Time Reversal for Indoor Propagation Channels

The experiments of time reversal (TR) technique with ultra-wideband (UWB) signals are conducted in indoor propagation channel by using time-domain technique. The UWB propagation channel response of a typical indoor environment is measured and time reversal technique is applied for signal transmission. The characteristics of the TR scheme for different propagation scenarios, line-of-sight (LOS) and non-LOS with different wideband receiving antennas are evaluated. The measurement results of signals focusing gain, temporal sidelobes and average signal energy for different propagation scenarios are presented. The spectral analysis of TR-UWB signals is conducted and an inherent bandwidth limit of the classical TR-UWB scheme is observed. To overcome the bandwidth restrictions, novel design architecture is proposed. The new design adjusts the TR signal by a way to support ultra-wide bandwidth and provides better matching to the UWB spectral mask with better temporal focusing features.     

超宽带冲激脉冲正交解调接收机系统反射校正算法及其实现

基于超宽带冲激脉冲的信号特征,提出了超宽带正交解调接收机系统中脉冲信号的反射模型与校正算法。通过时域瞬态传输线模型、信号流图模型分析,指出整个系统可等效为一个延时滤波网络。最后提出了拟合该等效延时滤波网络,求解其补偿网络的具体校正算法。在实际系统目标探测的外场试验中,也验证了模型分析与校正算法的正确性和有效性。     

A 0.25-mm CMOS T/R switch for UWB wireless communications

A T/R switch, fabricated using standard 0.25-/spl mu/m CMOS process, for ultra wide-band (UWB) wireless communications is presented. The switch is designed based on the concept of synthetic transmission line, utilizing both CPW and CMOS transistors, to achieve not only an extremely wide bandwidth but also a linear phase response necessary for time-domain UWB applications. On-chip measurement is completed in both frequency and time domains. Frequency-domain measured results show insertion loss of 2.2-4.2 dB, isolation from 34-48 dB, and highly linear transmission phase from 0.45 MHz to 13 GHz. These results are quite consistent with the calculations. Particularly, the time-domain pulse measurement shows that the output pulses resemble closely the input pulses with very little reflection, demonstrating the switch's suitability for true time-domain UWB applications. The developed switch is ready to be integrated with other CMOS RFICs to form on-chip transceivers for various UWB applications.     

超宽带载波包络调制及其频谱相关解调

针对超宽带载波包络调制的频谱特性,提出新颖的正交梳状频谱相关解调方法,将超宽带脉冲信号的处理从时域扩展到了频域。阐述了该解调方式的基本原理和设计思路,推导了正交梳状频谱的载波选择原则。对系统性能的分析和仿真证明了频域相关解调的方法有着和时域解调相同的误码率性能。该方法接收机结构简单、成本低,可由全数字电路实现,便于采用其它数字信号处理技术进一步提高系统性能。