漏泄同轴电缆与偶极天线的耦合范围研究

文章分析了障碍物对垂直开缝漏泄同轴电缆与偶极子天线之间耦合作用的影响,以漏泄同轴电缆为发射天线,偶极天线作为接收天线,详细分析了不同位置的障碍物对偶极天线接收电平的影响,进而确定障碍物影响耦合的范围。     

半环天线仿真建模及其性能测试分析

半环天线是车载短波常用天线之一。利用HFSS仿真软件对半环天线进行了基础建模,对该天线的反射损耗曲线和4个不同频率点的方向图进行了仿真,分析了不同频率对方向图的影响。利用实测数据对比分析了半环天线和三环天线的通信性能,实验结果表明半环天线能有效克服短波通信中的近距离盲区。     

复合材料垂尾隐蔽式短波天线研究

为研究复合材料垂尾对机载短波天线输入阻抗和辐射特性的影响,分析了不同机载隐蔽式短波天线的结构和性能,提出了一种基于复合材料垂尾的新型回线天线结构,并利用基于时域有限差分法的仿真软件XFDTD对这种位于机垂尾前缘的隐蔽式回线天线和传统的机载套筒天线分别进行了建模和仿真。根据仿真结果分析并总结出了复合材料垂尾对这两种机载短波天线输入阻抗和辐射特性的影响情况。通过与传统回线天线的比较,验证了新型回线天线的可行性和优势。仿真结果对实际机载短波天线的研究和设计有一定的参考价值。     

三线式短波宽带天线仿真分析及性能测试

针对常规短波天线的不足研制了一种三线式短波宽带天线。首先利用仿真软件HFSS对该天线进行了基础建模,然后对该天线在平拉架设和倒V架设时的反射损耗曲线和四个频率的方向图进行了仿真,分析了倒V架设时不同仰角对频率方向图的影响。最后利用实测数据对比分析了该天线和双极天线的通信性能,该天线具有通信范围广、增益高、辐射范围大等优点。     

中小功率短波台站天线的工作原理及实际运用

本文从对短波台站地概述、不同天线的性能对比、中小功率短波台站天线的工作原理及中小功率短波台站天线的假设方法等方面,对中小功率短波台站天线的相关问题进行了论述。     

短波天线工程设计实践

短波天线工程是短波收发信台固定台站开设的重要组成部分,对短波通信效能有很重要的影响。因此,论述了短波台站开设的台址选择、天线选择的要素及原则、工程设计依据等,并以某地区短波天线工程设计及实施为实例进行了实践论证,基本把握了短波天线工程设计施工的一般规律,具有一定的代表性。     

建筑物、地面对短波天线辐射特性影响的仿真分析

以鱼骨天线为实例，使用时域有限差分(FDTD)数值算法建立了鱼骨天线、建筑物和不同地面的仿真模型，分析并仿真了建筑物处于不同方位时对短波天线辐射特性的影响，以及不同地面对短波天线辐射特性的影响。数值仿真结果与参考文献和商用软件计算结果一致。     

复杂环境中短波天线的MoM/FDTD混合法分析

利用电磁场数值计算方法中的矩量法/时域有限差分（MoM/FDTD）混合方法,分析了复杂环境中短波天线的电磁辐射性能,建立了短波双极天线的自由空间模型。采用矩量法和时域有限差分法相结合,对其模型进行仿真计算,并将计算结果和已有的文献进行比较,验证了混合方法计算结果的可行性、准确性。总结了该模型对短波天线远区场影响的有益经验,为改善短波天线性能提供了设计参考。     

基于ITS模型的短波广播发射天线仿真分析

本文简述了短波广播发射天线的分类以及参数查询方法,介绍了使用ITS(Institute for Telecommunication Sciences)模型的天线仿真模块新建短波发射天线的过程,并利用新生成的天线文件对短波天波信号的覆盖区域进行了验证分析。     

基于反射系数的短波天馈线检测研究

短波天线体积庞大、线杆高度较高,馈线长度较长,检查维修较为不便。对短波天线馈线系统的检查和测试一直缺乏经济、有效的技术手段。提出根据短波天线馈线系统的传输特性,利用电波反射特点,运用定向耦合器分离入射波和反射波,计算短波天线馈线系统的当前反射系数,与其初始值进行比较,从而为判断天线馈线系统性能变化提供定量的参考数据,是一种检测短波天线馈线有效、经济的方法。     

Analyse d’antennes diélectriques par une méthode de diffraction

In order to approach the radiation problem of dielectric antennas, the authors study the scattering of electromagnetic waves by heterogeneous dielectric obstacles situated in the near-field zone of a circular waveguide carrying the TE₁₁ mode. By making use of the polarisation current densities and the free-space Green’s function, the integral equation concerning the electric field inside the obstacle is derived and then solved by the moments method. Results on the scattering by bodies of various shapes and structures are given as a function of the distance between the waveguide aperture and the scatterer. Finally the method is tested on dielectric antennas, i.e., the structures for which this distance vanishes.     

Analysis of aperture blockage in reflector antennas by usingobstacle-located blockage currents

An improved method is presented to account for blockage effects in the analysis of reflector antennas. Commonly this is done by introducing shadows on the reflector surface according to the location of the obstacles when performing the physical optics integration. By using physical optics blockage currents located at the blocking obstacle instead of at the main reflector surface, the effect of the different locations in the axial direction is accurately accounted for. This can easily be included by a single phase factor in existing computer programs based on physical optics integration     

Pattern synthesis of array antennas with additional isolation ofnear field arbitrary objects

A new technique for synthesising array antennas in the presence of arbitrary obstacles in the near field region is presented. This technique allows a prescribed far field pattern to be synthesised, while trying to avoid coupling with near field obstacles through the constraint of minimising the radiated power over the obstacle surface. Some results have been obtained showing that the obstacles are finally isolated from the array antenna radiation     

The influence of electromagnetic environment on operation of activearray antennas: analysis and simulation techniques

This paper presents an overview of active array antennas, system-level nonlinear effects in such antennas, and their modeling and simulation techniques. Advantages of active array antennas, in comparison with passive array antennas, are discussed. The influence of nonlinear distortions and interference in active antennas on the overall system performance is considered. Modeling and simulation techniques that can be applied to active array antennas are substantially different from those used for circuits and systems. Analytical and numerical techniques are used for the analysis of active antennas, with the prevailing use of numerical techniques at the present time. Electromagnetic-level and circuit-level simulation techniques are discussed. System-level simulation techniques are considered in detail, with special emphasis on their application to active array antennas. The “instantaneous” quadrature technique is proposed as an effective tool for numerical simulation of active arrays over wide frequency and dynamic ranges in a computationally-effective way     

标签天线弯曲对射频识别系统性能影响的研究

探讨了工作在微波段的无源射频识别(Radio frequencyIdentification, RFID)系统中标签天线的弧形弯曲对RFID系统性能的影响。分析比较了几种典型的半波振子标签线天线弧形弯曲的情况。通过理论分析确立标签天线的方向系数与输入阻抗为RFID系统性能的主要影响因子。弯曲振子天线特性参数由线天线分析软件NEC WinBasic数值模拟得到。分析结果表明,标签天线的弧形弯曲使得无源RFID系统的工作距离明显变短。因此,为避免此类问题有必要在RFID系统中考虑对于弯曲具有低敏感性的天线结构。     

基于微带天线的能量传输技术及其性能研究

对于安装在旋转部件上的监测系统来说,供能问题一直是一个难点。该文提出了一种基于微带天线的非接触式的能量传输技术,以代替传统的滑环或光电池等能量传输方法。该文以扭矩监测为应用背景,提出了能量传输系统的总体结构和天线馈源方案,并对天线的各种能量传输情况进行了研究,同时分析了旋转速度对能量传输的影响。     

Antenna Designer's Notebook-design curves for reducing the numberof phase shifters in-phased arrays by subarraying

A major obstacle in the realization of large-aperture phased array antennas is the associated large number of phase shifters. The number of phase shifters can be reduced by assigning several radiating elements to one phase shifter. Each such group is called a subarray. As the subarray size increases, the FOV (field of view, or beam-steering range) generally decreases. A set of design curves that can be used to optimize the tradeoff between field of view and subarray area is presented     

Redundancy concepts to increase transmission reliability in wireless industrial LANs

Wireless LANs are an attractive networking technology for industrial applications. A major obstacle toward the fulfillment of hard real-time requirements is the error-prone behavior of wireless channels. A common approach to increase the probability of a message being transmitted successfully before a prescribed deadline is to use feedback from the receiver and subsequent retransmissions (automatic repeat request-ARQ-protocols). In this paper, three modifications to an ARQ protocol are investigated. As one of these modifications a specific transmit diversity scheme, called antenna redundancy, is introduced. The other modifications are error-correcting codes and the transmission of multiple copies of the same packet. In antenna redundancy the base station/access point has several antennas. The base station transmits on one antenna at a time, but whenever a retransmission is needed, the base station switches to another antenna. The relative benefits of using FEC versus adding antennas versus sending multiple copies are investigated under different error conditions. One important result is that for independent Gilbert-Elliot channels between the base station antennas and the wireless station the antenna redundancy scheme effectively decreases the probability of missing a deadline, in a numerical example approximately an order of magnitude per additional antenna can be observed. As a second benefit, antenna redundancy decreases the number of transmission trials needed to transmit a message successfully, thus saving bandwidth.     

Ground influence on the input impedance of transient dipole and bow-tie antennas

In this paper, the influence of a lossy ground on the input impedance of dipole and bow-tie antennas excited by a short pulse is investigated. It is shown that the ground influence on the input impedance of transient dipole and bow-tie antennas is significant only for elevations smaller than 1/5 of the wavelength that corresponds to the central frequency of the exciting pulse. Furthermore, a principal difference between the input impedance due to traveling-wave and standing-wave current distributions is pointed out.     

各向异性衬底上的高温超导(HTS)微带天线

分析了各向异性衬底上的高温超导微带天线特性.选取两种典型的高温超导各向异性介质--GaNdAlO3和SrLaAlO4作为高温超导微带天线的衬底,采用各向异性媒质中的谱域矩量法,对微带天线的输入阻抗和辐射效率进行了计算.计算和分析结果表明,高温超导衬底的各向异性特性会影响高温超导微带天线的性能,而且这种影响因衬底而异,同时,衬底特性随温度的变化也将影响天线的性能.