高精度天线测试系统的研究与设计

为了使天线测试系统能有较高的测试精度,系统需具备水平圆周方向、俯仰方向和水平直线方向均可转动且转动精度非常高的天线转台;还需具备宽频率范围、高灵敏度的信号发射与接收处理装置;同时需具备操作方便、可精确控制天线转台和矢量网分仪以及能把测量的数据显示并保存、处理的测试软件。利用高精度天线转台和矢量网络分析仪,开发设计相应的自动测试软件,并进行天线相位中心的标定,为高精度天线相位中心的应用奠定了基础。     

某相控阵天线幅相分配网络的设计与实现

在某相控阵天线设计中,需要对铅垂放置的天线单元的方向图赋形.本文采用最小二乘法得到天线单无各振子电流的幅度和相位,并用MATLAB进行方向图计算仿真;根据计算结果,设计了幅相分配网络,并用HSFF仿真软件进行模型仿真;应用矢量网络分析仪对实物进行测量.测量结果表明,天线单元铅垂方向图与计算、仿真结果一致,满足设计要求.     

大张角宽带对数周期天线的优化设计

文章运用矩量法对大张角对数周期天线的电性能进行了分析.经过优化设计制作的大张角宽带对数周期偶极子天线(LPDA,Log Periodic Dipole Antennas),经测试测量值与计算值吻合得较好,已用于混波室测试.     

混波室测量技术

文章介绍了电磁兼容测量技术中的混波室测量技术.阐述了混波室的工作原理、理论分析模型、统计特性、混波室设计中的若干问题,以及混波室技术的现状和应用前景.     

搅拌器配置对混波室场影响的FDTD分析

混波室能提供统计均匀和各向同性的场,是一种用于辐射发射、屏蔽效能及敏感度测试等电磁兼容测试的小室。本文用FDTD方法分析混波室的场分布,分析了搅拌器不同大小及不同倾斜角度对混波室时间平均场分布的影响,为实际设计混波室的搅拌器提供参考。最后给出了与数值分析相一致的实验结果。     

强噪声环境下测量甚低频天线阻抗方法的研究

比较了在强噪声环境下测量甚低频发射天线输入阻抗二种方法, 提出一种新的矢量谐振测量方法, 这种新方法比传统的阻抗电桥法具有更高的精度.在此基础上研制出基于计算机数据采集与处理的天线输入阻抗实际测量系统, 该系统通过对测量网络各节点电压采样与处理, 自动计算天线输入阻抗并显示在计算机上.实测结果表明, 该系统具有优良的精度和稳定性.     

毫米波天线测量系统及测量精度分析

随着毫米波天线应用环境和设计复杂程度的不断增加,对毫米波天线的测量也提出了更高的要求,为适应宽频 带毫米波天线快速测量的需求,本文基于R&S 公司ZVK 矢量网络分析仪,研究了毫米波扫频紧缩场测量系统的特性, 针对影响其测量精度的主要因素进行了详细的分析讨论,阐述了系统改进主要方向,并给出了测量实例。     

矢量网络分析仪的时域功能在天线测量中的应用

介绍了利用矢量网络分析仪的时域功能测量天线系统驻波系数、增益和方向图的方法.这种方法通过确定各反射点的位置和反射大小,以及在天线增益和方向图的测量中去掉周围环境的反射影响,使测量的结果更精确.     

天线基本概念和原理实验教学设计与实现

针对教学中学生在理解天线基本概念和原理方面的困难,本文设计并实现了天线电参数测量实验。实验系统以矢量网络分析仪为基础,在微波暗室中搭建,具备天线方向图、增益和电压驻波比等参数测量功能。本文给出了系统配置和实验流程,并就如何基于天线测量系统开展相关教学工作进行了讨论。实践表明,实验教学是提高天线理论教学效果的有效手段。     

多速率超宽带通信系统中天线传输性能的研究

利用实验测量结合数值仿真的方法,研究了特定室内环境中,不同形状超宽带单极子天线对不同速率多带正交频分(MB-OFDM)超宽带通信系统传输性能的影响.仿真与实验中,MB-OFDM平台采用MATLAB的simulink工具实现,天线与传播环境构成的广义信道特性则通过矢量网络分析仪进行测量.结果表明,单极子天线形状对不同速率MB-OFDM系统的传输误比特率性能有显著影响,文章的方法可用于多速率超宽带通信系统收发天线的优选和性能评价.     

Evaluation of Transmit Antenna Position in Reverberation Chamber

The position of the transmit antenna is analyzed and evaluated according to the measurement data in our developed reverberation chamber. Nine calibrations are measured carefully. The key parameters such as field uniformity, quality factor, the average normalized electric field, and the receive antenna calibration factor are analyzed in detail. It is indicated that the position of the transmit antenna has insignificant influence on the test repeatability of calibrations     

Tradeoffs in the design of a spaceborne scanning pencil beamscatterometer: application to SeaWinds

SeaWinds is a spaceborne wind scatterometer to be flown on the second Japanese Advanced Earth Observing Satellite (ADEOS-II) in 1999. An important international element of NASA's Earth Observing System (EOS), SeaWinds is an advanced follow-on to the NASA scatterometer (NSCAT) on the first ADEOS platform. Unlike previous operational spaceborne scatterometer systems. SeaWinds employs a scanning “pencil-beam” antenna rather than a “fan-beam” antenna, making the instrument more compact and yielding greater ocean coverage. The goals of this paper are twofold. First, the overall SeaWinds functional design and backscatter measurement approach are described, and the relative advantages of the pencil-beam technique are outlined. Second, the unique aspects of measurement accuracy optimization and signal processing for the SeaWinds instrument are discussed. Applying the results of a separate companion paper, ibid., 1997, a technique to significantly improve measurement accuracy by modulating the transmit pulse is described. Trade-offs to optimize the transmit modulation bandwidth are presented     

室内分布式天线系统信道测量及容量分析

分布式天线系统通过在地理位置上分布式放置天线,增强了系统的覆盖性能,也提高了系统的分集增益和容量性能。通过自主搭建的信道测量平台,对室内分布式天线系统信道进行了测量,其中发端天线分布式放置,接收端天线集中放置,对数据分析表明,在不存在视距传输或者视距传输分量不明显的情况下,各发天线到收端的信道解相关特性良好,容量性能提高较大;反之则容量性能下降。系统容量与天线是否均匀放置也密切相关,天线均匀放置时,容量提高且分布更为均匀。     

基于单片机的天线测试参数数据采集与处理系统研究

天线是无线通讯系统中发射和接收电磁波重要的前端器件。本文在分析天线方向图测试原理的基础上,介绍了一种天线测试参数的信号采集和数据处理的系统。该系统以单片机MSP430为核心,由控制模块、数据采集模块和上位机通信模块是三部分组成,通过实际测量对计算结果进行验证,得出最接近理论预期的天线方向图。该系统具有硬件造价低,测量简便,测量精度较高的优点。     

A convenient technique for polarimetric calibration ofsingle-antenna radar systems

A practical technique for calibrating single-antenna polarimetric radar systems is introduced. This technique requires only a single calibration target such as a conducting sphere or a trihedral corner reflector to calibrate the radar system, both in amplitude and phase, for all linear polarization configurations. By using a metal sphere, which is orientation independent, error in calibration measurement is minimized while simultaneously calibrating the crosspolarization channels. The antenna system and two orthogonal channels (in free space) are modeled as a four-port passive network. Upon using the reciprocity relations for the passive network and assuming the crosscoupling terms of the antenna to be equal, the crosstalk factors of the antenna system and the transmit and receive channel imbalances can be obtained from measurement of the backscatter from a metal sphere. For an X-band radar system with cross polarization isolation of 25 dB, comparison of values measured for a sphere and a cylinder with theoretical values shows agreement within 0.4 dB in magnitude and 5° in phase. An effective polarization isolation of 50 dB is achieved using this calibration technique     

Length minimization of uniform linear antenna array for millimeter wave communications with maximum capacity

For uniform linear antenna array (ULA) based millimeter wave communications, the maximum capacity can be achieved by the optimal antenna separation product (ASP). However, due to the practical size limitation, it is necessary to decrease the ULA length. In this paper, an optimization problem is formulated to minimize the ULA length for millimeter wave communications with maximum capacity. We decompose the problem into two subproblems: length selection optimization and orientation deployment optimization. The optimal length selection can be obtained when the transmit and receive ULAs have equal length. By using the property of trigonometric function, we derive the optimal orientation deployment and study the influence of orientation deviation on ULA length. Simulation results are presented to validate the analyses.     

A New Technique for Measuring FM & TV Antenna Systems

Described here is a measuring system using a computer controlled network analyzer that allows observation of FM and TV broadcast antenna systems. Impedance measurement may be made at any point in a broadcast antenna system where access is possible. Most notably, the VSWR characteristics of an antenna on a tower may be measured from the ground without the effects of the transmission line. Measurement accuracy is 0.1 DB and 0.5 degree return loss with excellent repeatability. The system is suitable for field use allowing evaluation of the antenna and other parts of the RF system.     

Radio Propagation Model Considering Antenna Beam Tilt with Application to Small Cells

Antenna beam tilting techniques are commonly used to deploy small cells with reduced coverage compared than macrocells. This paper proposes a new statistical propagation model for small cells with electrical and mechanical antenna tilt. The proposed model combines the dual slope path loss model with the departure angle spread model for considering antenna beam tilt. The proposed departure angle spread model introduces a new parameter reflecting the azimuth spread of departure (ASD) angles in order to account for the change of transmit antenna gain by electrical and mechanical tilt. Through this approach, the antenna gain for each ray is separately computed by considering the transmit antenna beam pattern as well as the antenna beam tilt. We perform field tests to measure the receive signal power in the downlink of commercial Long-Term Evolution small cells with antenna tilt. Based on the measurement data, we find the statistically optimal ASD parameter using a grid search and calculate the antenna gain for each ray. Also, the overall transmit antenna gain is obtained by averaging antenna gains for multiple rays. To assess the accuracy of the proposed model, the estimation error is evaluated by comparing the measured receive signal power with the estimated value using a propagation model, and the performance of the proposed propagation model is compared with those of existing path loss models in terms of root mean square error deviation. Then, it is shown that the proposed model provides more accurate propagation estimation for small cells than existing models.     

电磁兼容天线参数定义及其相互关系

运用图示法简述了电磁兼容天线参数的基本概念。给出了在电磁兼容测量中,EMC 天线参数之间的相互关系及其计算公式,如天线系数和发射天线系数的计算、功率密度和电场强度的计算、天线辐射场强的计算、功率与电压之间的转换计算和功率密度与电场强度之间的转换计算等等。     

无线传感器网络中的整流天线技术研究进展

本文介绍了适用于无线传感器网络的、能进行无线输能的整流天线和能进行无线定位的时间反演算法.适用于无线传感器网络的整流天线要求紧凑的天线结构,高效的微波能量到直流电量的转换效率以及较高的入射波频率.利用时间反演算法的时-空聚焦特性,可解决无线传感器网络中节点无线定位问题,以提高整流天线的效率.