多极化低频UWB SAR图像的失真补偿

多极化、低频、超宽带合成孔径雷达（UWB SAR）可以获得目标的多极化散射特性,并具有一定的叶簇穿透能力,是未来雷达技术发展的一个重要方向.为了获得较高的方位向分辨率,该系统通常具有较大的方位向处理角,因此天线方向图沿方位向的变化不能忽略.该系统的超宽带特性使得天线方向图随频率的变化也不能忽略.本文假定天线方向图完全已知,提出了多极化低频UWB SAR的系统模型,并在图像的变换域上实现对天线方向图的补偿.最后利用计算机仿真验证了该方法的有效性.     

一种Ⅹ-KU波段TSA天线设计

渐变开槽天线（Tapered Slot Antenna）具有宽频带、结构灵巧、易于电路集成和组成相控阵列等优点,但是通过分析和设计常规的指数型TSA天线,发现其存在后瓣和旁瓣较大、增益较低的缺点.通过改进天线整体结构和局部开槽的方法,优化了常规TSA天线表面和渐变槽线边缘的电流分布,并利用HFSS设计了一付工作于X波段、KU波段改进型TSA天线,与设计的常规天线TSA相比,天线主辐射方向3dB波瓣宽度增大,最大增益提高,后瓣和副瓣得到了一定的抑制.     

m=0角向模表面波等离子体柱天线辐射特性

根据表面波在非磁化等离子体柱中的色散关系,理论计算得到存在电子-中性原子碰撞、径向与轴向等离子体密度非均匀分布条件下m=0角向模表面波波矢实部与虚部随信号频率、等离子体密度的变化关系.然后利用波矢的实部与虚部、等离子体柱天线表面指数分布电流模型、等离子体阻抗,推导得到等离子体柱天线的辐射方向图随信号频率、等离子体密度的变化关系;最大增益、天线辐射阻抗随信号频率的变化关系;天线径向能量辐射随等离子体密度的变化关系.理论计算结果表明等离子体柱天线辐射方向图随信号频率、等离子体密度的改变而变化非常明显,信号频率对最大增益、天线辐射阻抗的影响显著;同时,这些理论计算结果与他人实验实测结果吻合,这对于设计高精度要求的等离子体天线提供了重要的理论参考价值.     

一种X-KU波段TSA天线设计

渐变开槽天线(Tapered Slot Antenna)具有宽频带、结构灵巧、易于电路集成和组成相控阵列等优点,但是通过分析和设计常规的指数型TSA天线,发现其存在后瓣和旁瓣较大、增益较低的缺点。通过改进天线整体结构和局部开槽的方法,优化了常规TSA天线表面和渐变槽线边缘的电流分布,并利用HFSS设计了一付工作于X波段、KU波段改进型TSA天线,与设计的常规天线TSA相比,天线主辐射方向3dB波瓣宽度增大,最大增益提高,后瓣和副瓣得到了一定的抑制。     

一种基于微带槽天线的带阻性UWB天线的研究

提出了一种新颖的小型平面超宽带天线。该天线由微带槽天线的基本结构变形而来,为获得超宽带的频率特性,设计时馈电微带采用了圆弧形调谐枝节,金属底板的开槽设计成对称多边形之后通过数值计算获得最佳的天线几何尺寸。通过HFSS仿真和测试设计了一种频率覆盖3.1～10.6 GHz的超宽带UWB天线,其对包含在超宽带频段范围内的民用频率范围有一定的滤除作用,结构简单并且驻波特性良好,方向图具有准全向性。     

电磁波激励下天线的响应特性分析

应用互易定理推导出了电磁波激励下天线的耦合长度和耦合面积的表达式,这两个物理量可以表征天线的响应特性.针对对称振子天线,在不同来波照射方向和端接不同带宽的接收机这两种情况下,计算获得了耦合长度和耦合面积.计算结果表明,工作频率为2GHz的对称振子天线的耦合长度随着接收机带宽的变化在频率f=2 4n (GHz) (n=0,1,2...)或f=4n (GHz) (n=1,2...)附近出现谐振峰;而耦合面积随来波入射角度的增大而增大,随接收机带宽的减小而减小.     

天线隔离度的频率依赖特性

明确地指出了在计算2个不同频系统的天线隔离度时,天线的功率效率和方向图是随频率变化的,一些情况下是需要使用天线在失配区特性的;详细地阐述了一种估算单频段垂直极化偶极子阵列结构的基站天线方向图参数随频率变化的方法;通过计算电磁学仿真对该方法进行了验证;实际测量实验也表明隔离度和天线频率特性是密切相关的。     

一种具有陷波特性的多模态频率可重构UWB天线

为了应对在超宽带(Ultra-Wide Band, UWB)系统中频率可重构天线尺寸偏大、模式单一等问题,提出了一种具有陷波特性的多模态频率可重构UWB天线。该天线通过在圆形单极子的辐射贴片上添加T型枝节和刻蚀I型槽、倒U型槽,以获得UWB覆盖范围为2.7～11.6 GHz的宽阻抗带宽,并产生四个陷波带。仿真与实测表明：控制PIN二极管的偏置状态,可以实现单频段、双频段、三频段、四频段和五频段共五种频段下八种工作模式的多模态切换。此天线大小为16 mm×19 mm,较传统单极子天线体积减小了40%以上,实现了小型化。天线的最大增益为4.13 dBi,具有良好的辐射特性。     

一种新型超宽带天线的设计

针对无线通信系统对超宽带(Ultra-Wideband,UWB)天线小型化的需求,提出了一种同轴馈电的UWB天线,由常规的椭圆单极子天线演变而成.为了获得UWB特性,天线的辐射单元由7个完全相同的椭圆单极子合理组合而成.该天线印刷在相对介电常数为4.4、 厚度为1.6 mm的FR4介质板上,并通过同轴进行馈电,天线的结...     

超宽带双圆锥天线的FDTD分析

UWB(Ultra-Wide Band超宽带)技术是新一代的无线电通信技术,具有低功耗,高带宽,并且相对简单的特点,在低费用的中短距离的无线通信应用中越来越具有吸引力.该研究可望用于UWB系统的一种超宽带天线-双锥天线.采用FDTD法分析了不同锥角的天线,给出了它们的频域反射损耗结果.     

Low-cost small-size tapered slot antenna for lower band UWB applications

A low-cost small-size tapered slot antenna (TSA) is investigated in view of ultra-wideband (UWB) applications. First, the bandwidth of the antenna is studied for the lower UWB band: 3.1-4.85 GHz. Secondly, the design is made as small as possible. Thirdly, the pulse distortion of a modulated Gaussian pulse in the lower UWB band, between 3.5 and 4.5 GHz, is investigated based on the measured S/sub 21/-parameter. The low distortion observed indicates that this TSA is suitable for applications in the lower UWB band.     

Ultra-wideband tapered slot antenna with band cutoff characteristic

A novel ultra-wideband (UWB) tapered slot antenna (TSA) is proposed that has both enhanced impedance bandwidth enough to cover UWB systems and band cutoff characteristic of 5 GHz WLAN band limited by IEEE802.11a and HIPERLAN/2. To achieve these two characteristics of wide bandwidth and partial band cutoff at the TSA, a broadband microstrip-slotline transition with multi-arm stubs and /spl lambda//4 short stubs, respectively, is used. From measured results, it is observed that wide bandwidth of about 2 octaves from 2.8 to 11.09 GHz for the VSWR<2 is achieved, while 5.05-5.93 GHz is cutoff with the radiated power of this cutoff band effectively suppressed as about -9 dB for the peak power level of other bands.     

一种可折叠的米波超宽带天线阵列设计

扩大槽线单元开口渐张的比例因子并优化其他参数,压缩天线尺寸,采用金属框架结构,结合镂空和局部切割方法,实现米波超宽带天线单元小型化和轻量化设计。双极化单元正交排布,通过单元分步折叠和阵列骨架分块折叠,实现大型阵列天线自动化撤收与架设。实验阵列口径超过18 m×6 m,可在15 min 内实现快速折叠或展开。实验天线的测试结果与设计一致,表明分析与设计方法正确有效,可推广应用于各种宽带天线及大型阵列天线设计。     

小型平面超宽带天线的研究进展

对小型平面超宽带(UWB)天线的研究现状进行了分析总结.首先介绍超宽带无线通信的技术背景,描述了超宽带天线的几种常见定义.然后分别对小型超宽带印刷单极子天线的设计、小型超宽带缝隙天线的设计、具有陷波功能的小型超宽带天线的设计进行了详细的评论,并讨论了超宽带天线的性能评价方法.最后展望了小型平面超宽带天线的未来研究方向.     

On the Impact of Ultra-Wideband (UWB) on Macrocell Downlink of UMTS and CDMA-450 Systems

Results of the analytical analysis to assess the effect of the ultra-wideband (UWB) emissions on the [universal mobile telecommunication system (UMTS) and code division multiple access systems (CDMA-450)] are presented. The (UMTS and CDMA- 450 systems) normalized range and normalized capacity degradation are evaluated. A free-space propagation model is used to calculate the UWB signal power that interferes with both mobile systems. It is shown that, for the case of a single UWB transmitter, the UMTS can easily tolerate UWB interference when the UWB equivalent isotropically radiated power (EIRP) is -92.5 dBm/MHz or less for a distance between the UWB transmitter and the UMTS mobile of 1 m or higher. Also, it is shown that, for the case of multi-UWB transmitters, the UMTS can easily tolerate the UWB interference when the UWB EIRP is -94.5 dBm/MHz. For the single UWB transmitter case, the CDMA-450 downlink can tolerate UWB interference when the UWB power density is in the order of -106 dBm/MHz. For the case of multi-UWB transmitters, the power density that can be tolerated by the downlink of the CDMA- 450 system is in the order of -108 dBm/MHz.     

An overview of ultra wide band indoor channel measurements and modeling

In this paper, an overview of reported measurements and modeling of the ultra wide band (UWB) indoor wireless channel is presented. An introduction to UWB technology and UWB channels is provided. Different UWB channel sounding techniques are discussed and approaches for the modeling of the UWB channel are reviewed. The available indoor UWB channel measurement results are consulted and accordingly, the major UWB channel parameters are presented and compared to those of narrowband systems. The novelty of this work is the gathering of different UWB channel parameters, analysis, and comparison. Added with the influence of UWB antenna in channel-modeling as well as the frequency-dependency of the channel parameters, leading to a conclusion on the UWB radio channel modeling.     

超宽带技术在未来无线通信中的应用

首先给出了超宽带技术(UWB)的概念,详细叙述了超宽带技术的基本原理和研究现状,阐述了超宽带的关键技术及在未来无线通信中的应用,给出了超宽带技术的技术规范、技术要求和国内外超宽带技术中关键技术的研究现状和面临的挑战,最后介绍了超宽带技术的发展动态。     

超宽带平面天线技术

对近年来发展的超宽带平面天线技术进行了综述,依次介绍了超宽带平板单极天线、超宽带印刷单极天线和超宽带印刷缝隙天线的进展,并作了比较.最后也介绍了具有带阻功能的超宽带印刷天线..     

超宽带通信中的天线技术

超宽带（UItra-wide Bandwidth,UWB）短距离无线通信是近几年来的一个热门课题。UWB技术具有高保密性、低功耗等一系列特点,在众多领域都有很好的应用前景。UWB天线作为其中的一项关键技术,也得到了广泛的研究。本文就超宽带中的天线技术作一个简单介绍以便更深的了解超宽带系统。     

Coexistence Between UWB and Narrow-Band Wireless Communication Systems

Ultra-wide-band (UWB) signals are suitable for underlay communications, over a frequency band where, possibly, other systems are active. Such coexistence of UWB and other systems is possible if the mutual interference has a small impact on their respective performance. This paper aims to present recent results on the interference and coexistence among UWB systems and other conventional narrow-band (NB) systems. Specifically, we consider a point-to-point UWB (NB) link under the interference generated by a finite number of NB (UWB) radio transmitters. We consider channels including additive white Gaussian noise and multipath fading both for the victim and the interfering links, and different receiver architectures. While our main focus is on UWB systems based on impulse radio, wide-band systems employing carrier-based direct-sequence spread-spectrum and orthogonal frequency-division multiplexing are also considered.