数字多波束天线的校准测试方法

针对数字多波束天线所特有的多波束性能测试和精密测距性能校准的需求,结合数字多波束天线的工作原理,分析比较了基于远场和近场的2种校准和测试方法,提出了数字多波束天线波束指向、波束电平和相位中心的修正方法,并结合实际系统完成了试验验证。试验结果表明:该测试和校准方法可高效率完成数字多波束天线系统的校准和测试工作,提高系统的测量精度,具有很强的实用价值。     

一种辐射发射近场测试系统方案的设计与优化

辐射发射(RE)的设计和远场测试整改复杂、成本高,为了解决中小规模公司缺乏低成本、简单的近场摸底测试系统的问题,设计验证了一种基于数字示波器的近场辐射发射测试系统,可用于获取远场RE102测试的频谱走向和趋势,使产品的EMI认证成本减少1/3,试验周期缩短1/5.为远场测试整改难度大、成本高的问题提供了一种解决方案.     

基于PNA多通道扫频近场测量速度与精度分析

为适应宽频带多波束天线快速测量的需求,基于Agilent新型矢量网络分析仪PNA系列,研究了多通道扫频近场测量系统的特性,针对系统的测量速度和精度问题进行了详细的分析讨论,并对系统的动态范围、接收机的幅相漂移、测量的位置误差等主要误差源进行了分析,给出了提高测量精度的方法。该方法有效地降低了测量时间,提高了近场测量系统的测试效率。     

有源多波束天线方向图测试方法研究

论述了利用高精度三轴天线测试转台,测试有源多波束天线立体方向图的方法。简述了天线立体方向图的测量程序。给出了用二维坐标表示多波束立体方向图的方法,并简述了利用MATLAB软件对测试数据进行处理获得多波束天线立体方向图的方法,对方向图测试误差进行了分析。最后,给出了某工程有源多波束天线方向图的测试结果。实践证明:该方法是切实可行的。     

天线平面近场测量中一种近远场变换方法研究

本文研究了一种应用于天线平面近场测量中完成近远场变换的数值算法。利用此方法可以依据天线平面近场测试数据快速简便地求得天线远场方向图及其它特性,其精度较高;同时可以很方便地进行探头修正,并讨论天线平面近场测试中各关键参数对测试结果的影响。本文给出了理论依据和具体计算实例,与传统方法进行了比较,并得出了结论。     

天馈系列行业标准建设的作用及影响

天馈系列行业在世界上首次完整规范了对采用直接远场方法测试天线辐射参数的验收、场地及设备要求、鉴定级测试场地和设备要求,首次引入了多探头球面近场测量方法,规范近场场地及设备要求,首次规范了对天线环境与可靠性的测试场地和仪表要求.     

多探头球面近场天线测试效率提升方法

为最大化提升球面近场测试效率,针对多探头球面近场测试系统的不同采样方案进行了研究,并通过仿真和测试对比了不同采样方案对测试效率的影响.首先利用电磁仿真软件计算出所设计喇叭天线的近场和远场方向图数据;然后利用基于球模式展开法的近场到远场变换算法,从理论上验证了在满足采样规则的前提下,通过适当增加方位上的采样间隔可实现测试...     

基于平板电路的无源互调耦合测试方法

无源互调(PIM)是一个吸引众多领域研究人员的课题,包括卫星、天线和智能终端等。本文提出一个非接触式PIM测量的新思路：使用一个经过近场重构的基片集成缝隙波导(SISW)作为互调信号的激励和接收路径,SISW通过对载波信号的远场抑制和近场测试区的优化,实现了一种针对没有射频端口的样品非线性特性的评估解决方案。该测试平台结合了近场天线的有限辐射特性和多敏度测试区在PIM评估中对收发系统和测试样片的适应性。实验结果表明,该测试方法在稳定性和分辨力方面具有相当大的工程应用潜力。     

天线时域平面近场测试的误差分析

天线时域近场测试技术对误差体系研究的缺失,导致测试结果的不确定度分析一直无法完成.为解决这一问题,以天线时域平面近场测试为例,对时域近场测试的误差进行研究,给出时域测试区别于频域测试技术的四个误差项:探头调制误差、信号源稳定度误差、时间采样间隔误差、时间采样长度误差.在给出误差项后,对误差的产生机理进行了讨论,通过仿真和实测给出了误差对测试结果的影响.     

平面近场诊断在相控阵天线通道幅相性能测试中的应用

传统的平面近场诊断在通道测试时由于互耦,得到的检测值为所有通道叠加的结果,不利于单个通道信息的提取。为了去除互耦,提出了矢量旋转和近场口面诊断相结合的方法,理论上能实现对相控天线单个单元的幅度相位的检测。对该方法进行误差分析,得到了各个误差源对该方法的影响大小。通过实验验证,证明了该方法有效地减小了互耦影响,能提取单个通道的近场、远场信息,并能为相控阵天线通道校准和故障检测提供有效的手段。     

Far-field uncertainty due to random near-field measurement error

Recent planar near-field scanning tests with ultralow-sidelobe antennas have confirmed that random near-field measurement errors will ultimately limit the accuracy of far-field patterns. A formulation is outlined for estimating the spectral signal-to-noise ratio (SNR) arising from noncorrectable near-field random measurement errors. The formulation applies to arbitrarily directive test antennas and probes-even nulling probes. A far-field parameter, called the scan plane coupling factor, may be computed directly from the near-field data, and then used to form the spectral SNR. The accuracy of the spectral SNR is confirmed by simulation and by actual tests with low-sidelobe AWACS array antenna     

Antenna measurements using a hologram CATR

It becomes increasingly difficult to obtain far-field measurements for large millimetre wave antennas at higher frequencies due to the required large distance between the antennas. A hologram compact antenna test range (CATR) is used to determine the radiation characteristics of a 39 GHz planar antenna in a small facility. The results are compared with those obtained from planar near-field scanning and conventional far-field measurements     

Analysis of phase-focused near-field testing for multiphase-centeradaptive radar systems

Airborne or spaceborne radar systems often require tests before deployment to verify how well the system detects targets and suppresses clutter and jammer signals. The radar antenna diameter can be large and thus the conventional far-field test distance is impractical to implement. The theory and simulations of phase-focused near-field testing for adaptive phased array antennas is discussed. With near-field source deployment, standard phased-array near-field phase focusing provides far-field adaptive nulling equivalent performance at a range distance of one aperture diameter from the adaptive antenna under test. Both main beam clutter sources and sidelobe jammer sources are addressed. The phased array antenna elements analyzed are one-half wavelength dipoles over the ground plane. Bandwidth, polarization, array mutual coupling, and finite array edge effects are taken into account. Numerical simulations of an adaptive antenna that has multiple displaced phase centers indicate that near-field and far-field testing can be equivalent     

Characterization of Real-World Steered-Beam Antennas from Amplitude-Only Near-Field Data

Phase-less near-field techniques are becoming increasingly more important for antenna characterization, due to the growing interest in millimeter-and sub-millimeter-wave applications, where the near-field phase is difficult or even impossible to measure. In this framework, the routine application of phase-less near-field/far-field (NFFF) transformations to real-world operational antennas is a challenging problem, recently questioned in the literature, requiring algorithms capable of providing reliable and accurate results over a large class of radiators. In the present paper, the possibility of applying phase-less near-field techniques for routine testing of antennas is discussed. We point out how -following the recent developments in the field, and by a formulation of the problem based on proper representations of unknowns and data - it is possible to gain the reliability and the accuracy required for this. Experimental tests were carried out on steered-beam antennas, which have lately been pointed out as "difficult" workbenches, to test the feasibility of operational phase-less near-field/far-field transformations. The experimental results refer to a reflectarray radiating a tilted beam, and to a phased array of large electrical dimensions, radiating a scanned beam and actually employed in real-world applications.     

Radial field retrieval in spherical scanning for currentreconstruction and NF-FF transformation

A near-field to far-field (NF-FF) transformation is addressed for the case of spherical scanning using equivalent magnetic currents (EMCs) and matrix methods. It is based on the decoupling of the field components and the iterative retrieval of the radial component of the electric field. The technique is applied for far-field calculation as well as for the estimation of the current distribution of the antenna under test (AUT) using spherical near-field facilities. Results from measured near-field data of several antennas are presented and compared to those of the analytical solution via a spherical wave mode expansion method     

Near-field diagnostics of small printed antennas using theequivalent magnetic current approach

A near-field to far-field transformation based on the antenna representation by equivalent magnetic current (EMC) sources has been proposed and validated experimentally on large high-directivity antenna arrays. In this paper, the use of EMC is extended to the diagnostics of low-directivity printed antennas. The limitation of the near-field to far-field transformation applied to EMC models of low-directivity antennas, caused by the finite dimensions of the antenna ground plane, is demonstrated. A method to partially overcome this limitation by including the contribution of diffracted rays is implemented, and its effectiveness is demonstrated with antenna prototypes. It is shown that the agreement between the far-field patterns measured in an anechoic chamber and the patterns computed from the EMC model obtained from the near-field measurements is significantly improved upon, within a sector of ±90° with respect to the antenna boresight in the E plane. The influence of the near-field sampling density and topology of the EMC model on the accuracy of the predicted far-field pattern is examined     

Near-field probe used as a diagnostic tool to locate defectiveelements in an array antenna

Results of an experimental study are presented in which the near-field probe was used as a diagnostic tool to locate the defective elements in a planar array. The near-field data were processed not only to obtain the far-field patterns of the array under the test, but also to reconstruct the aperture field for diagnostic purposes. The backward transform enables the near-field probe to identify accurately aperture faults at a distance, free of interactions and couplings with the array elements. In practice, to recover the aperture field properly from the near-field distribution, the evanescent components in the computed far-field spectrum must be excluded from the inverse process with fast-Fourier-transform (FFT) techniques. For low-gain array antennas, a correction on the far-field spectrum is required to remove the contribution of the probe and the element factor before the inverse transform, strongly enhancing the resolution     

Evaluation of adaptive phased array antenna, far-field nullingperformance in the near-field region

A theory for analyzing the behavior of adaptive phased array antennas illuminated by a near-field interference test source is presented. Conventional phased array near-field focusing is used to produce an equivalent far-field antenna pattern at a range distance of one to two aperture diameters from the adaptive antenna under test. The antenna is assumed to be a linear array of isotropic receive elements. The interferer is assumed to be a bandlimited noise source radiating from an isotropic antenna. The theory is developed for both partially and fully adaptive arrays. Results are presented for the fully adaptive array case with single and multiple interferers. The results indicate that near-field and far-field adaptive nulling can be equivalent. The adaptive nulling characteristics studied in detail are the array radiation patterns, adaptive cancellation, covariance matrix eigenvalues, and adaptive array weights     

Evaluation des cadences de mesure de champs proches au moyen de sondes modulées

The problems involved in the direct far-field measurements of large antennas have led to the development of the near-field measurement technique. According to this method, the far-field pattern of the antenna is calculated from the near-field measurements close to the antenna. The only inconvenience in this technique is the slow rate of measurements. This slowness is due to the mechanical displacement of the measuring probe or the test antenna. The modulated scattering technique is a method to reduce the measurement time while preserving acceptable levels of accuracy. This article is mainly concerned with estimating the possible measurement rates in typical configurations.