平面近场测量中取样位置误差修正方法的研究

本文提出一种修正近场天线测量中探头集团误差的方法－非线性迭代法。探头的集团误差为可知值,同激光定位系统获得。运用泰载级数展开,可将天线理想波谱表示为误差算子和近场测量数据的形式。通过计算机械模拟,得到迭代修正后精确的近场值。本文在理想值、有误差的值和修正误差后的值之间作了些比较,相应的模拟数据有助于证实此结合。     

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.     

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。     

模式滤波技术在平面近场天线测量中的应用

为了修正平面近场测量中的多次反射误差,介绍了模式滤波修正技术在平面近场测量中的应用,提出了一种合适的模式滤波函数.推导出模式滤波修正技术的相关公式并进行了数值仿真,仿真结果表明通过利用模式滤波技术对平面近场天线测量结果进行后处理能够有效地改善测量结果.     

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.     

平面近远场变换的快速算法

基于考虑探头补偿的平面近远场变换理论 ,根据实际需要 ,提出了一种工程实用的平面近远场变换快速算法。通过该算法由近场测量数据变换得到的天线远场方向图 ,既能达到任意分辨率 ,又能节约计算内存和提高计算速度。     

天线近远场变换的快速算法

基于考虑探头补偿的平面近远场变换理论,根据实际需要,提出了一种工程实用的平面近远场变换快速算法。通过该算法由近场测量数据变换得到的天线远场方向图,既能达到任意分辨率,又能节约计算内存和提高计算速度。     

平面近场测量的共轭梯度法分析

从被测天线(AUT)和探头的耦合方程出发，利用Nyquist定理，推导出了扫描面上近场和波谱函数之间的矩阵方程。用共轭梯度法(CG)求解这一矩阵方程，得到波谱函数，从而算出远场方向图。这种方法只需要知道测量点的位置就足够，并不要求测量点必须位于某些特定点上。计算结果表明，用此方法原理上可消除常规平面近场测量中位置误差的影响。     

时域近场测试中的探头误差分析与修正

探头误差分析和修正是时域近场测量中的关键技术.本文详细推导了探头自身接收特性误差函数在修正过程中的坐标变换关系,提出用 '时间窗' 技术隔离掉探头和待测天线之间的多重反射波,并导出'时间窗’的选取原则,数值结果证明了理论和方法的有效性.     

平面近场中极化偏差的修正方法

本文从实际工程应用出发,结合电磁场理论,系统的阐述了平面近场中极化偏差的修正方法。并基于椭圆极化波的分解理论,提出了利用椭圆极化长轴倾角修正因测试探头和待测天线的极化偏差造成的测试误差。实验结果验证了该方法的有效性。     

Accurate determination of planar near-field correction parametersfor linearly polarized probes

A procedure used by the US National Bureau of Standards (NBS) for accurately determining the plane-wave receiving parameters of both single- and dual-port linearly polarized probes is described. Examples are presented, and the effect of these probe receiving characteristics in the calculation of the parameters for the antenna under test is demonstrated using the required planar near-field theory. The planar near-field theory necessary to accomplish probe correction and to formulate probe parameter errors is presented in a concise and meaningful way to help understand when probe correction is or is not needed     

An overview of near-field antenna measurements

After a brief history of near-field antenna measurements with and without probe correction, the theory of near-field antenna measurements is outlined beginning with ideal probes scanning on arbitrary surfaces and ending with arbitrary probes scanning on planar, cylindrical, and spherical surfaces. Probe correction is introduced for all three measurement geometries as a slight modification to the ideal probe expressions. Sampling theorems are applied to determine the required data-point spacing, and efficient computational methods along with their computer run times are discussed. The major sources of experimental error defining the accuracy of typical planar near-field measurement facilities are reviewed, and present limitations of planar, cylindrical, and spherical near-field scanning are identified.     

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.     

Near-field antenna measurements using nonideal measurementlocations

We introduce a near-field to far-field transformation algorithm that relaxes the usual restriction that data points be located on a plane rectangular grid. Computational complexity is O(Nlog N) where N is the number of data points. This algorithm allows efficient processing of near-field data with known probe position errors. Also, the algorithm is applicable to other measurement approaches such as plane-polar scanning, where data are collected intentionally on a nonrectangular grid     

Strategy to avoid truncation error in planar and cylindrical near-field antenna measurement setups

A simple and effective method to avoid the truncation error in antenna near-field measurements is presented. The method can be applied to planar or cylindrical near-field setups, whenever it is possible to vary the distance between the antenna under test and the probe during the scanning procedure.     

Displacement errors in antenna near-field measurements and theireffect on the far field

The effects of probe displacement errors in the near-field measurement procedure on the far-field spectrum are studied. Expressions are derived for the displacement error functions that maximize the fractional error in the spectrum for both the on-axis and off-axis directions. The x- y- and z-displacement error in planar scanning are studied and the results are generalized to errors in spherical scanning. Some simple near-field models are used to obtain order-of-magnitude estimates for the fractional error as a function of relevant scale lengths of the near-field, defined as the lengths over which significant variations occur     

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.      

基于最小二乘法的平面波综合

将最小二乘法引入近场天线测量中,提出了一种新的平面波综合方法。以半波对称振子组成的矩形平面阵作为平面波综合的理论模型,用这一新方法寻求阵列单元的最佳幅相分布,以使所综合出的准平面波质量最好。计算结果表明在待测区域大小一定的条件下,利用本文方法可以实现较传统方法更小的探头阵列要求。良好的仿真结果证实了该方法在天线测量及散射测量应用中的有效性。