Compact antenna test range without reflector edge treatment and RF anechoic chamber

There are several types of CATRs (compact antenna test ranges) used in antenna-pattern measurements. An offset reflector is generally used to generate the quiet zone of a CATR. Serrated edges, rolled edges, or R-cards are generally chosen along the reflector's edge to reduce the edge-diffraction field inside the quiet zone of the CATR. In order to reduce stray signals from the environment, a high-quality RF anechoic chamber is required for a CATR. In this paper, a new type of CATR, without either a reflector edge treatment or an RF anechoic chamber, is developed. A commercially available DBS (direct-broadcast satellite) reflector antenna, without edge treatment, is used as the reflector antenna of the CATR to generate the quiet zone of the antenna test range. In order to improve the quiet zone's performance, the fields due to feed spillover, edge diffractions, and other stray signals are gated out by the ITDAMS (impulse time-domain antenna measurement system). The RF interference in the environment can also be reduced by time synchronization and pulse integration of the impulse time-domain antenna measurement system. In order to verify the capabilities of the proposed CATR, three kinds of antennas (a low-directivity horn antenna, a high-directivity 60 cm direct-broadcast satellite reflector antenna, and a 25 cm Ka-band Cassegrain LMDS - local microwave distribution system - antenna) were measured by the proposed CATR. The antenna-pattern results agreed quite well with those of a near-field range and a far-field range.     

An open-boundary quad-ridged guide horn antenna for use as a source in antenna pattern measurement anechoic chambers

The present paper introduces a new antenna design to be used in anechoic chambers. When measuring three-dimensional patterns, the receiving antenna in the anechoic chamber must be able to sense the two orthogonal components of the field that exist in the far field. This can be accomplished by mechanically rotating the source horn in the chamber. A better and faster approach is to use a dual-polarized antenna and to electronically switch between polarizations. This new design is a broadband (2-18 GHz) antenna with dual polarization. The antenna is a ridged guide horn. The novel part is that the sides have been omitted. Numerical analysis and measurements show that this open-sided or open-boundary horn provides a better and more stable pattern behavior for the entire band of operation, as well as good directivity for its compact design. The radiation and input parameters of the antenna are analyzed in this paper for the novel design as well as for some of the early prototypes to show some of the ill effects of bounded quad-ridge horn designs for broadband applications. Mechanically, the antenna is built so that it can be mounted onto the shield of an anechoic room without compromising the shield integrity of the chamber.     

基于压缩感知的天线远场快速测量技术

提出一种应用于天线远场测量系统的压缩感知方法,通过使用正交模拟信息转换(QAIC)结构,可以减少对数据样本的采集,缩短测量时间,并提高天线远场测试效率。为验证系统的准确性,在微波暗室中,测量标准角锥喇叭天线的远场方向图,控制正交模拟信息转换结构的测量数据采样量,低速均匀采样,获取到信号的观测数据,并采用优化算法重构恢复信号。实验表明,该系统在满足一定测量误差的条件下,减少70% 的数据采集量仍能保证测量结果的准确性,较传统暗室测试更高效。     

暗室条件下抗干扰测试结果影响分析

暗室为卫星导航接收机抗干扰测试提供了全面有效的测试环境，极大地提高了抗干扰性能定量测试与评估能力。但暗室的静区性能、结构尺寸、天线布局等因素会对抗干扰性能测试结果产生影响。基于多径信号天线接收模型、阵列波程差等效模型和信号来向天线映射模型，通过仿真量化分析了干扰多径信号、有限距离下近场效应和来波方向误差对抗干扰测试结果的影响。结果表明，暗室静区性能的提升可降低干扰多径信号对零陷位置的拉偏；不同暗室尺寸对应不同的零陷深度测试，需根据测试需求折中选择；布设暗室天线应依据预设的被测阵列天线和测试场景。结果可为暗室设计、抗干扰测试方案选定和测试结果分析提供参考，提升抗干扰测试的可信度。     

一种高精度多通道天线测试系统

天线测量是天线研究过程中一项重要而又繁杂的工作,在对高性能雷达天线的研制过程中,离不开一套高精度的天线测试系统。影响天线测试系统精度的因素很多,从测量环境微波暗室、天线发射控制系统、天线接收控制系统等几方面设计了一种多通道天线测试系统,用来测量和分析天线辐射特性的各种电磁参数。设计完成的测试系统具有测 量灵敏度高、动态范围大、测量误差小、抗干扰能力强和天线原始数据采集速度快的特点,具有一次性扫描测量就可获得多频点、多通道天线数据的能力。     

微波暗室有限测试距离对天线远场测量的影响

利用电磁场和误差分析理论,在阐述天线远场测量条件的基础上,分析了微波暗室有限测试距离对天线远场测量的影响,建立了误差模型,并结合实例说明了微波暗室有限测试距离对天线场强测量、增益测量的影响.分析结论可为实践中快速准确地确定适合在微波暗室内进行测量的天线尺寸和频率范围提供具体的技术指导.     

Design and construction of a multipurpose wideband anechoic chamber

An electromagnetic anechoic chamber has been constructed at the Multimedia University. It is designed to operate over a very wide frequency range from 30 MHz through 18 GHz. It can be used for electromagnetic compatibility (EMC) tests, antenna measurements, radar cross section (RCS) measurements, testing RF transceivers, calibration of scatterometers, and other electromagnetic research experiments. The geometry of the chamber is asymmetrical, consisting of a combination of rectangular and tapered volumes. The size of the chamber is about 64 ft /spl times/ 32 ft /spl times/ 24 ft high. Ease of construction and ease of lining of the absorbers were preserved so that the actual quietness is comparable to the theoretical simulation result. The transmitting source is placed at one end of the chamber, and the receiving antenna or object under test is placed in a designated quiet zone at the other end. The walls and ceilings are configured such that no first-order and or second-order reflections (except those reflected from the floor) propagate into the quiet zone. Hence, less-expensive absorbers can be used to achieve the required wideband performance. Reflection from the floor is required by the international EMC standards for radiated electromagnetic interference (EMI) emission tests; therefore, the chamber is designed for this capability. However, absorbing material can be placed on the floor to convert a semi-anechoic chamber into a fully anechoic chamber for radar and antenna measurements.     

Effects of External PIM Sources on Antenna PIM Measurements

Antenna Passive Intermodulation (PIM) level measurement results are rarely credited to be due to external signal receiving characteristics of the antennas or serious effects from external PIM sources, such as the anechoic chamber absorber and antenna tower. This paper presents an antenna PIM model for a reflected PIM measurement method. Based on the findings of null point generation and the behavior of the third order PIM values obtained by theoretical predictions and experimental results, we concluded that the results of the antenna PIM level test were influenced by the external PIM sources generated by the anechoic chamber absorber and the path differences of PIM signals coming into the antenna.     

微波暗室静区性能仿真预测方法

为了有效预测微波暗室的静区性能,使用FEKO软件进行任意入射角度条件下角锥吸波材料的前向反射率仿真,并以某矩形暗室结构为例,利用吸波材料反射率仿真结果,采用射线追踪法计算了发射天线位于天线阵面上典型位置时暗室静区内反射电平的分布情况.经比较,仿真结果与实际测量结果一致性较好,该方法为微波暗室性能预测提供了有效手段.     

Measurement of electrically large array antennas in small anechoic chambers [Measurements Corner]

A post-processing procedure that yields accurate array-antenna radiation-pattern estimations is described. By resorting to this strategy, measurements of large array antennas inside small anechoic chambers become feasible. The method employs an adequate phase-correction derived from an optical ray approach, under the assumption that the elementary radiators themselves are electrically small and can be measured under far-field conditions inside the relevant anechoic chamber. The effectiveness of the proposed technique is demonstrated by examining the case of a nonuniform linear array antenna.     

一种基于微波暗室的大角域卫星导航接收机测试场景构建方法

提出了一种基于微波暗室的大角域测试场景构建方法,该方法利用已有42射频面阵,采用多状态联合校准方法对面阵天线单元到接收机的信号幅度和相位进行校准,以及采用灰色关联分析方法将外界环境下的卫星星座、动态干扰在微波暗室内实现逼真映射,构造最大视场角为160的半实物抗干扰测试场景。仿真测试结果表明:暗室天线单元与实际场景下的卫星星座在角域关系下最大误差在高增益3 dB 波束宽度内,暗室模拟的动态干扰与实际环境下到达接收机的功率基本一致;最后实现了对多波束抗干扰接收机的测试,并通过干信比与有效载噪比的关系曲线说明了该方法能够在室内实现导航接收机测试环境的逼近模拟,并准确地测试出多波束接收机的抗干扰性能。     

Characteristics of a tapered anechoic chamber

The characteristic features of a tapered anechoic chamber are described. The smooth illumination amplitude in the chamber makes it usable as an indoor range for antenna pattern measurements, even at low frequencies. Variations in the transmission attenuation in the chamber as compared to free space require careful interpretation of absolute gain and cross section data.     

应用于卫星导航与对抗的穹形满天星暗室的仿真设计

针对当前信息化战争背景下卫星导航装备对无线测试环境的应用需求,结合现阶段国内外暗室发展现状,对矩形、穹形两种暗室进行选型分析,从静区特性、应用性能等方面进行系统仿真分析,最终采用穹形暗室作为暗室选型方案。通过满天星天线布局,模拟真实环境中的卫星轨迹和信号,构建与真实环境高度逼真的无线测试环境,能够有效支撑卫星导航装备尤其是波束成形抗干扰终端的测试,填补了国内在穹形满天星暗室方面的设计空白,可指导工程实践应用。     

基于距离差分法消除天线测试多径干扰

在暗室中对天线进行测量时,来自暗室侧壁、后墙的多径干扰会影响测试精度。因此多径干扰成为影响天线测量精度的主要因素之一。为此,提出利用距离差分法消除天线测试时的多径干扰,达到去除多径干扰的目的。并通过数值仿真验证了该方法是行之有效的。     

无人机通信干扰电磁环境半实物仿真系统

针对战场环境下复杂传播环境及敌方干扰对无人机通信系统性能的影响,提出了综合信道衰落和干扰共同作用下的无人机通信信道理论模型。在此基础上,基于微波暗室设计实现了无人机通信干扰电磁环境半实物仿真系统。该系统利用硬件现场可编程门阵列(Field Programmable Gate Array,FPGA)实时模拟无人机通信信道和干扰信号,利用微波暗室模拟外场的无线传播环境,并通过天线位置和角度调节装置模拟发射机、干扰机和接收机之间的空间位置特性。实测结果表明,该半实物仿真系统能够真实复现无人机通信干扰电磁环境,可用于无人机数据链抗干扰性能的测试和评估。     

Portable radio antenna performance in the 150, 450, 800, and 900MHz bands `outside' and in-vehicle

Portable radio antenna performance on the human body was measured for several different radio models in the 150, 450, 800, and 900 MHz. bands. In-vehicle measurements were made at an outdoor antenna range equipped with a vehicle turntable. All other measurements were made in an anechoic chamber. Tests were made at the head level, at the side-level swivel-type carry case, at the side-level belt-loop type carry case, and at the shoulder level with a speaker microphone antenna. A statistical analysis was made of the data for use in coverage propagation predictions, and system designs. The results of the statistical analysis are presented     

“三元组近场”新型幅度控制精确算法

在电磁辐射和散射测量时，为使目标处于平面波照射区，被测目标和天线的距离应满足远场条件。但是在一些电子战设备进行暗室内性能测试时，根据这些设备的工作波长和天线口径，则需要建造很大的微波暗室，事实是在很多情况下是不现实的。为此，详细推导了一种“三元组近场”条件下的幅度控制精确算法，该算法能将辐射式仿真远场测试距离降低约1倍，实现近场效应修正，可以广泛应用于工程实践。     

Two methods for the measurement of antenna efficiency

Two methods for measuring antenna efficiency are described. The two methods, referred to as the Wheeler method and theQmethod, are used to find the efficiency of electrically small multiturn loop antennas. The principal advantage of both methods is that they can be quickly and easily applied. Further, both methods relate the antenna efficiency to the input impedance rather than a far-field pattern integration. Thus, the methods are applicable at VHF and frequencies below where the design of an antenna range or anechoic chamber becomes increasingly difficult and expensive.     

用于UHF频段的RFID波束扫描阵列天线设计

为了扩大射频识别系统阅读范围和提高识别效率,设计了一款应用于多标签高效读取的射频识别( RFID)波束扫描阵列天线。采用空气层结构设计出增益值为6 dBi的圆极化天线阵元并组成2×2平面天线阵,使用开关线型移相器与威尔金森(Wilkinson)功分器设计出天线馈电网络,并使用现场可编程门阵列(FPGA)模块控制阵元间相位变化,实现波束30°偏转。整体模型尺寸为350.0 mm×350.0 mm×5.7 mm,分别使用微波暗室、射频网络分析仪以及连接RFID阅读器测试,表明天线实现了4个方向波束偏转以及识别多个标签。     

微波暗室静区性能的测量方法

本文给出了使用自由空间驻波法进行微波暗室静区性能测量的基本原理,并以实际测量为例,给出了使用对数周期天线、矢量网络分析仪对一矩形微波暗室静区性能进行测量的详细步骤及检验方法.本文对微波暗室的建设、使用和维护具有一定的指导意义,对使用微波暗室进行天线和微波后向散射测量也有一定的参考意义.