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.     

基于Gerchberg-Papoulis算法的平面近场截断误差修正方法研究

在平面近场天线测量中,有限扫描面截断是影响测量精度的主要误差源之一,找到解决截断误差的方法是天线测量的研究重点之一.文中将平面近场天线测量中由有限区域内的场求平面波谱的过程抽象为带限函数外推的数学模型,从实际测量中的近远场变换理论出发,论证了GP（Gerchberg-Papoulis）算法应用在平面近场测量中在理论上是切实可行的.将GP算法应用在平面近场天线测量中,并分析了不同迭代次数算法的修正情况.结果表明,随着算法迭代次数的增多,可信角域外计算方向图与理论方向图差别明显减小.因此,本文的方法能够明显减小平面近场测量中截断误差的影响.除此以外,还分析了误差对算法收敛性的影响,结果表明,误差对算法修正效果影响较大.     

基于单元电流重构的平面近远场变换

本文提出了一种新的基于单元电流重构的平面近远场变换方法,给出了该方法的基本原理.计算机模拟结果表明,这种方法不要求取样间隔一定要满足奈奎斯特取样准则,只需较少的取样点数即可达到很高的测试精度,从而能够在保证测试精度的前提下,提高测试速度并有效减小由于有限扫描面所引起的截断误差.因此,本文方法特别适合于大型相控阵天线的平面近场测量.     

平面近场天线多任务测试系统工程设计

提出了一种平面近场天线多任务测试系统的工程设计方法,该方法通过增加多功能天线测试控制器和远控微波开关对传统平面近场测试系统进行升级,使其具备对平面相控阵雷达天线多频点、多波位、多通道一次最多可测试35个天线方向图的测试能力。对新引入的幅相误差及扫描面截断误差进行了计算分析。大型相控阵天线的实测结果表明,在提高测试效率的同时,其测试精度亦能满足测试要求。     

中场测量相控阵扫描方向图的方法研究

有源相控阵天线的发射和接收天线的性能依赖于阵面口径的幅相分布，有源相控阵的幅相校准工作通常在出厂前通过暗室中的平面近场测量进行，但是某些大型的有源阵面根本无法进暗室进行校准，利用外场测量进行的校准往往无法验证其结果的好坏，该文介绍了一种中场测量相控阵天线扫描方向图的方法，使校准结果能够得到较为客观的评估。     

平面波谱恢复算法在平面近场测量中的应用

介绍用于天线平面近场测量的一种近远场变换新算法。该法利用被测天线的平面波谱和口径场幅相分布之间的关系,以及天线口面的约束条件,用G-P迭代算法从平面波谱的置信谱域部分恢复出置信谱域外的平面波谱。这种方法减小了较小截断角下有限扫描面对测量精度的影响,并提高了天线近场测量的效率。     

有源相控阵天线近场测试方法研究

天线测试是有源相控阵雷达设计中的重要组成部分,介绍了平面近场测试系统的搭建和测试方法,以及利用平面近场测试系统的口面场进行反演,从而快速测试出有源相控阵雷达天线波瓣的相关性能,实测某Ku天线副瓣电平低于-25d B,扫描指向精度,增益等指标满足设计指标要求。为完成宽带有源相控阵天线的性能测试提供了有效的方法。     

天线平面近场测量扫描架的位移控制

平面近场测量是天线测量的一种重要方法,而平面近场扫描架是天线近场测量系统中的关键设备,对它的控制直接关系到整个近场测量系统的成败。本文介绍了一种天线平而近场测量系统中扫描架的结构,工作原理及控制方法。实践证明,这种控制方法完全满足系统要求。     

减小平面近场测量中多次反射误差的新方法

本文给出了用平面近场技术测量超低副瓣天线时,平面近场测量总误差与天线远场方向图副瓣电平的误差方程,并进行了计算机仿真;提出了减小平面近场测量中探头天线与待测天线间多次反射误差和微波暗室电特性误差对超低副瓣天线所引入的测量误差的"自校准法",实验结果说明该方法是解决平面近场测量中多次反射和微波暗室电特性误差较为理想的方法.     

时域平面近场测量的近场分析

本文以Ｈ面喇叭为例,研究了天线时域近场的运动状态,用谱域法分析了平面近场分布状况,得出采样原则,为平面近场扫描测量提供了理论依据,并为平面近远场变换打下了基础。     

Reduction of Truncation Errors in Planar Near-Field Aperture Antenna Measurements Using the Gerchberg-Papoulis Algorithm

A simple and effective procedure for the reduction of truncation errors in planar near-field measurements of aperture antennas is presented. The procedure relies on the consideration that, due to the scan plane truncation, the calculated plane wave spectrum of the field radiated by the antenna is reliable only within a certain portion of the visible region. Accordingly, the truncation error is reduced by extrapolating the remaining portion of the visible region by the Gerchberg-Papoulis iterative algorithm, exploiting a condition of spatial concentration of the fields on the antenna aperture plane. The proposed procedure is simple and computationally efficient; it does not require any modification of the measurement procedure and it allows for the usual probe correction. Far-field patterns reconstructed from both simulated and measured truncated near-field data demonstrate its effectiveness and stability against measurement inaccuracies.      

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     

FD-TD法用于环形相控振子天线阵列的数字模拟

本文论述了FD-TD法用于电磁辐射系统的近场计算问题,用该方法实现了对环形相控振子天线阵列的数字模拟。作为对方法的检验首先计算了单个振子天线上的电流分布,还计算了环中充满去离子水时阵列的近区场及其与人体躯干块状模型的相互作用。     

Planar near-field scanning in the time domain .2. Sampling theoremsand computation schemes

For part 1 see ibid. vol.47, no.9, p.1280 (1994). Two computation schemes for calculating the far-field pattern in the time domain from sampled near-field data are developed and applied. The sampled near-field data consists of the values of the field on the scan plane measured at discrete times and at discrete points on the scan plane. The first computation scheme is based on a frequency-domain near-field to far-field formula and applies frequency-domain sampling theorems to the computed frequency-domain near field. The second computation scheme is based on a time-domain near-field to far-field formula and computes the time-domain far field directly from the time-domain near field. A time-domain sampling theorem is derived to determine the spacing between sample points on the scan plane. The computer time for each of the two schemes is determined and numerical examples illustrate the use and the general properties of the schemes. For large antennas the frequency-domain computation scheme takes less time to compute the full far field than the time-domain computation scheme. However, the time-domain computation scheme is simpler, more direct, and easier to program. It is also found that planar time-domain near-field antenna measurements, unlike single-frequency near-field measurements, have the capability of eliminating the error caused by the finite scan plane, and thus can be applied to broadbeam antennas     

Element gain pattern prediction for finite arrays of V-dipoleantennas over ground plane

The element gain pattern for finite phased arrays of dual-polarized crossed V-dipole antennas over ground plane is addressed. The method of moments is used to predict the center-element gain pattern. An experimental, 19-element, passively terminated planar array is described, and center-element gain pattern measurements are presented. The theoretical results are in good agreement with measurements     

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