窗函数在相控阵天线平面近场测量中的应用

有限扫描面截断是影响天线平面近场测量精度的主要误差源之一，尤其是对于波束扫描的相控阵天线的平面近场测量更是如此。为了减小相控阵天线平面近场测量中的有限扫描面截断误差，介绍了余弦窗函数并将其应用到相控阵天线平面近场测量中。计算机模拟结果表明，通过对近场进行加余弦窗的数据处理能够有效地减小有限扫描面截断误差。提出了对近场数据进行加余弦窗处理的适用条件。     

Reflector radiation pattern from planar near-field measurements of array feed

High gain shaped beam antennas for satellite frequency reuse applications are almost exclusively obtained by the use of complex multielement feed arrays to provide pattern control in conjunction with offset reflectors to remove blockage effects. In the design of complex multielement feed arrays for offset reflectors, the element excitations are usually synthesized using the isolated element properties. Proper performance of the array often requires that these theoretical excitations be modified to account for the effects on the feed elements due to the array environment. Near-field planar probing of the fields of the feed array have been found to provide an efficient and accurate method of predicting the secondary performances, including cross polarization and axial ratio. The nearfield measurement technique, moreover, provides an extremely effective method of determining the element performance and for determining the required compensation for desired antenna performance.     

随机误差对超低副瓣天线平面近场测量的影响

导出了平面近场测量中近场幅相随机误差所引起的误差谱的解析表达式。利用计算机模拟和统计平均的方法研究了近场幅相随机误差对超低副瓣天线平面近场测量结果的影响 ,并给出不同口径尺寸的超低副瓣天线的平面近场测量 ,为保证- 5 5 d B副瓣± 5 d B的测试精度 ,所能允许的近场幅相随机误差的最大起伏度     

墙壁散射对超低副瓣天线平面近场测量的影响

以二维问题为例，基于平面波谱展开理论和几何光学近似，利用计算机模拟的方法研究了暗室墙壁散射对超低副瓣天线平面近场测量的影响，得到了一些基本的规律和有用的结果。     

Virtual array synthesis method for planar array antennas

A new array antenna synthesis method, which we call the virtual array synthesis method, is presented. In this method, the excitation values of a virtual array are synthesized using some known synthesis method. The geometry of the virtual array can be chosen so that there will be a suitable synthesis method for that geometry and the synthesis of the virtual array can be done accurately enough. In the synthesis method presented, the excitation values of the virtual array are transformed into the excitation values of the actual array geometry. Matrix operations are simple and large arrays can be easily synthesized     

The bi-polar planar near-field measurement technique, part II:near-field to far-field transformation and holographic imaging methods

A novel customized bi-polar planar near-field measurement technique is presented in a two-part paper. This bipolar technique offers a large scan plane size with minimal “real-estate” requirements and a simple mechanical implementation, requiring only rotational motions, resulting in a highly accurate and cost-effective antenna measurement and diagnostic system. Part I of this two-part paper introduced the bi-polar planar near-field measurement concept, discussed the implementation of this technique at the University of California, Los Angeles (UCLA), and provided a comparative survey of measured results. This paper examines the data processing algorithms that have been developed and customized to exploit the unique features of the bi-polar planar near-field measurement technique. Near-field to far-field transformation algorithms investigated include both interpolatory and non-interpolatory algorithms due to the a typical arrangement of the bi-polar near-field samples. The algorithms which have been tailored for the bi-polar configuration include the optimal sampling interpolation (OSI)/fast Fourier transform (FFT), Jacobi-Bessel transform, and Fourier-Bessel transform. Additionally, holographic imaging for determination of antenna aperture fields has been incorporated to facilitate antenna diagnostics. Results for a simulated measurement of an array of infinitesimal dipoles and a measured waveguide-fed slot array antenna are included. Appropriate guidelines with respect to the advantages and disadvantages of the various processing algorithms are provided     

一种减小相控阵天线球面近场测量截断误差的方法

在相控阵天线球面近场测量中,有限扫描面和相控阵天线波束扫描将会引起较大的截断误差.为了解决这一问题,提出利用基于遗传算法参数优化的余弦窗函数对近场数据进行加权处理的方法来有效减小截断误差.以半波振子组成的矩形平面阵作为待测天线,对相控阵天线球面近场测量进行了计算机模拟.模拟结果表明,通过对近场数据进行加余弦窗的处理并用遗传算法对参数进行优化能够大大减小相控阵天线波束扫描时的有限扫描面截断误差,从而证实了文中所提出方法的正确性和有效性.     

近场测量相控阵天线的全息成像方法

研究了一种利用近场测量技术全息成像相控阵天线口径幅相的方法。该方法是把近场测量获得的方向图函数与由单元形式及幅相分布表示的方向图函数进行比较,采用FFT算法和空间域的Fourier重构法,可以快速、精确地成像出相控阵天线口径的“全息图”,进而诊断出阵中单元幅相的奇异程度。通过仿真实验,检验了该方法的成像分辨率和精度,并考察了不同口径区域的成像误差对辐射方向图的影响程度,说明该具有非常好的应用前景。     

Error analysis techniques for planar near-field measurements

A combination of techniques is described for reliably estimating the magnitude of each error arising in planar near-field measurements. They include mathematical analysis, computer simulation, and measurement tests. There are three primary applications for these tests: in designing a measurement facility, the requirements of each part of the measurement system can be specified to meet a given level of accuracy; during actual measurements, the experimenter can identify, and reduce where necessary, potential sources of error in the measurement; and when a measurement has been completed, the estimated uncertainty in the measurement can be obtained with confidence and ease. The latter application has been used in many measurements to verify that the planar near-field technique produces high-accuracy results competitive with any other measurement technique     

一种多波束面阵天线的分析与设计

介绍了二维多波束天线的特点和实现二维多波束的几种方法，针对空馈的Rotman透镜推导出了由它馈电的平面天线阵的相位计算公式及设计方法，在此基础上成功地实现了空馈透镜的平面天线阵样机，并给出了相应的测试结果。     

A new technique for planar array antennas synthesis

A novel technique, conceived and baptized the immunity tactic will be presented in this paper. As one will see, we classify the technique under the stochastic processes while governed by deterministic rules. This technique was greatly inspired by the immune activity, which has the tendency to eliminate the strange bodies and to preserve the self-organism. The analogy with the synthesis will be as follows:

• Elimination of all the weak solutions.

• Preservation of the best solution.

Some biologic immunity operators will be borrowed and adapted to our technique, which remain governed by deterministic rules to avoid any destabilization.     

Far-field patterns of spaceborne antennas from plane-polar near-field measurements

Certain unique features of a recently constructed plane-polar near-field measurement facility for determining the far-field patterns of large and fragile spaceborne antennas are described. In this facility, the horizontally positioned antenna rotates about its axis while the measuring probe is advanced incrementally in a fixed radial direction. The near-field measured data is then processed using a Jacobi-Bessel expansion to obtain the antenna far fields. A summary of the measurement and computational steps is given. Comparisons between the outdoor far-field measurements and the constructed far-field patterns from the near-field measured data are provided for different antenna sizes and frequencies. Application of the substitution method for the absolute gain measurement is discussed. In particular, results are shown for the 4.8-m mesh-deployable high-gain antenna of the Galileo spacecraft which has the mission of orbiting Jupiter in 1988.     

扫描波束天线无相位近场测量技术

以寻找高频扫描波束天线近场测量方法为目的, 提出了一种结合差分进化算法和迭代傅里叶变换算法的双平面无相位近场测量方法.首先用线极化探头在近区采集正交方向切向场幅值信息; 其次使用差分进化算法寻找合适的初始迭代相位; 再利用迭代傅里叶变换算法对一扫描面上的相位进行还原; 最后使用采样幅值和还原相位结合近远场变换理论求得天线远场方向图.为验证方法可行性, 以对称振子天线阵为模型, 对不同扫描角时的测量过程进行仿真, 均获得良好结果.     

Scan-plane reduction techniques for planar near-field antenna measurements

In this work, two planar near-field scan-plane reduction techniques are considered and results are presented. It is shown how truncation based on field-intensity contours, instead of simple geometric truncation, can in some cases improve the efficiency of the truncation process. Both techniques are applied to measured data sets, and it is shown how these methods can be used to reduce data-acquisition times, while also assessing the impact of the total acquisition surface reduction on the far-field radiation-pattern integrity.     

Nonuniformly spaced linear and planar array antennas for sidelobe reduction

The material discussed can be divided into two parts. In the first part, an iteration method is presented for calculating the distances between the elements of a symmetrical nonuniformly spaced linear array antenna for sidelobe reduction. The amplitude of the excitation is assumed to be constant. The iteration method is applied to linear array consisting of 24 elements. After a few iterations, the sidelobe-to-mainlobe power ratio was reduced to over 22 dB from its value of 13.2 dB for uniform array spacing. In the second part, several symmetrical nonuniformly spaced planar array antennas have been designed, using the nonuniform linear array spacings of part one. The planar arrays include square-shaped and circular structures, with the number of elements ranging from 284 to 576. The iteration method discussed can be applied to linear arrays with any number of elements to obtain nonuniform grid spacings for sidelobe reduction. A number of planar grid structures can be constructed using the nonuniform linear grids. The nonuniform linear and planar arrays utilize fewer radiating elements and result in desirable sidelobe structures.     

Application of spherical near-field measurements to microwaveholographic diagnosis of antennas

Microwave diagnosis of antennas is considered as a viable tool for the determination of reflector surface distortions and location of defective radiating elements of array antennas. A hybrid technique based on the combination of the spherical near-field measurements and holographic metrology reconstruction is presented. The measured spherical near-field data are first used to construct the far-field amplitude and phase patterns of the antenna on specified regularized u-v coordinates. These data are then utilized in the surface profile reconstruction of the holographic technique using a fast-Fourier-transform (FFT)/iterative approach. Results of an experiment using a 156-cm reflector antenna measured at 11.3 GHz are presented for both the original antenna and the antenna with four attached bumps. Several contour and gray-scaled plots are presented for the reconstructed surface profiles of the measured antennas. The recovery effectiveness of the attached bumps has been demonstrated. The hybrid procedure presented is used to assess the achieved accuracy of the holographic reconstruction technique because of its ability to determine very accurate far-field amplitude and phase data from the spherical near-field measurements     

Prediction of far-field from uniform and non-uniform under-sampled near-field data in planar near-field antenna measurements

In near-field antenna measurements various forms of uniform and non-uniform sampling techniques have been widely deployed. Considering the fact that the near-field pattern of any antenna is a spatially quasi-band-width-limited function of space coordinates, Shannon's theorem simply defines the sampling frequency. Based on the sampling theorem, in order to precisely reconstruct a band-limited signal from its samples, the sampling frequency must be at least twice as much as the signal's bandwidth. Through the simulations and theoretical evaluations this research shows that if the near-field pattern is either uniformly or non-uniformly under-sampled due to any practical reasons, yet a good estimation of far-field pattern can be obtained especially if the antenna under test (AUT) is a directive high-gain or super high-gain antenna. Also the time efficiency of far-field prediction from under-sampled near-field data is discussed and the advantages and disadvantages are highlighted.     

矩形栅格圆口径平面相控阵天线方向图计算

针对机载相控阵雷达天线受机头圆柱形设备舱约束的条件,研究了矩形栅格圆口径平面相控阵天线的方向图,建立数学模型并对其进行了公式推导和计算机仿真。同时将该天线与同等规模的矩形口径平面阵天线方向图特性进行了对比分析,结果表明:前者通过展宽主波束宽度和抬高旁瓣间交叉电平深度获得了优于后者的抗干扰性能的结论。     

FDTD simulations and measurements for cell phone with planar antennas

The Finite-Difference Time-Domain (fdtd) method is used to calculate the cellular phone far and near field and the specific absorption rate (sar) in the user’s head. The conventional λ/4 monopole and a simple planar antenna are simulated and measured. The simulated results are in good agreement with those measured for thevswr and for the radiation patterns on the horizontal and vertical planes. These results show that significant improvements in the antenna radiation efficiency and in the reduction of thesar in the head are obtained when planar antennas are used.