共查询到20条相似文献,搜索用时 15 毫秒
1.
Schmidt C.H. Leibfritz M.M. Eibert T.F. 《Antennas and Propagation, IEEE Transactions on》2008,56(3):737-746
Near-field antenna measurements combined with a near-field far-field transformation are an established antenna characterization technique. The approach avoids far-field measurements and offers a wide area of post-processing possibilities including radiation pattern determination and diagnostic methods. In this paper, a near-field far-field transformation algorithm employing plane wave expansion is presented and applied to the case of spherical near-field measurements. Compared to existing algorithms, this approach exploits the benefits of diagonalized translation operators, known from fast multipole methods. Due to the plane wave based field representation, a probe correction, using directly the probe's far-field pattern can easily be integrated into the transformation. Hence, it is possible to perform a full probe correction for arbitrary field probes with almost no additional effort. In contrast to other plane wave techniques, like holographic projections, which are suitable for highly directive antennas, the presented approach is applicable for arbitrary radiating structures. Major advantages are low computational effort with respect to the coupling matrix elements owing to the use of diagonalized translation operators and the efficient correction of arbitrary field probes. Also, irregular measurement grids can be handled with little additional effort. 相似文献
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Raimund Mueckstein Chris Graham Cyril C. Renaud Alwyn J. Seeds James A. Harrington Oleg Mitrofanov 《Journal of Infrared, Millimeter and Terahertz Waves》2011,32(8-9):1031-1042
We demonstrate that the integrated sub-wavelength aperture probe designed for THz near-field scanning probe microscopy can be used to map surface plasmon waves at THz frequencies. Observed near-field images of metallic patterns reveal surface plasmon waves superimposed over THz transmission images. We discuss the coupling mechanism for the surface waves and arrive to an important conclusion that the detected surface wave images represent the spatial derivative of the surface plasmon electric field. The relationship between the electric field and the measured signal is confirmed experimentally by mapping surface waves in bow-tie antennas. This study explains previously observed effects in THz near-field microscopy and provides a framework for analysis of near-field images. 相似文献
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《Antennas and Propagation, IEEE Transactions on》2009,57(5):1382-1390
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《Antennas and Propagation, IEEE Transactions on》2008,56(11):3485-3493
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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。 相似文献
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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 相似文献
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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 相似文献
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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 相似文献
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《Antennas and Propagation, IEEE Transactions on》2008,56(9):2981-2987
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In near-field techniques applicable to large antennas the measurements are often made through the scanning of a meridian of the desired surface for different orientations of the test antenna. Utilisation of a probe array permits a rapid analysis of the field along that meridian. As shown in this paper, it is not necessary to stop the movement of the antenna during measurements along the meridian, if a simple scheme for continuous rotation of the test antenna is utilised. 相似文献
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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. 相似文献
13.
Bolomey J.-C. Cown B.J. Fine G. Jofre L. Mostafavi M. Picard D. Estrada J.P. Friederich P.G. Cain F.L. 《Antennas and Propagation, IEEE Transactions on》1988,36(6):804-814
Key results are summarized of efforts to significantly reduce the near-field measurement time by utilizing one- or two-dimensional arrays of modulated scattering probes in lieu of the single probe ordinarily used in conventional near-field measurement techniques. Results of analytical, numerical, and experimental investigations show that the modulated-scattering technique (MST) using arrays of hundreds or even thousands of modulated scattering probes can be used to map the complex near-field of antennas or scatterers in a few seconds or minutes. The results also strongly indicate that classical (nonmodulated) receiving/transmitting arrays can be adapted for rapid near-field data collection. Major factors affecting the accuracy and speed of probe arrays for near-field measurement are delineated and discussed. Experimental results obtained using laboratory prototype MST systems are also presented and discussed 相似文献
14.
《Electromagnetic Compatibility, IEEE Transactions on》1986,28(4):170-178
In electromagnetic-susceptibility testing of electronic equipment, the ideal incident field is a plane wave. To approximate this condition, a seven-element array of Yagi-Uda antennas has been constructed and tested at a frequency of 500 MHz. The element weightings are determined by a near-field synthesis technique, which optimizes the uniformity of the field throughout a rectangular test volume in the near field of the array. The amplitude and phase of the electric field have been measured throughout the test volume with a short-dipole probe, and the agreement with the theory is excellent. 相似文献
15.
Capozzoli A. Ciotola R. Curcio C. D'Elia G. De Colibus I. Liseno A. Vinetti P. 《Antennas and Propagation Magazine, IEEE》2007,49(6):113-122
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. 相似文献
16.
Liang W. Hygate G. Nye J.F. Gentle D.G. Cook R.J. 《Antennas and Propagation, IEEE Transactions on》1997,45(5):772-780
We describe an optically modulated scatterer as an electric-field probe for measuring radio-frequency and microwave fields. It has a high spatial resolution and the ability to operate very close to conducting and dielectric objects without appreciable distortion of the field to be measured. Thus, it can scan close to antennas and diffracting metal structures. We describe how the electric field is deduced from the measurements and present gain measurements and far-field patterns deduced from near-field scans of antennas. The results are tested by comparing them with those obtained by established measurement techniques 相似文献
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Mohammed Adnan Salhi Alireza Kazemipour Gennaro Gentille Marco Spirito Thomas Kleine-Ostmann Thorsten Schrader 《Journal of Infrared, Millimeter and Terahertz Waves》2016,37(9):857-873
We present the design and characterization of planar mm-wave patch antenna arrays with waveguide-to-microstrip transition using both near- and far-field methods. The arrays were designed for metrological assessment of error sources in antenna measurement. One antenna was designed for the automotive radar frequency range at 77 GHz, while another was designed for the frequency of 94 GHz, which is used, e.g., for imaging radar applications. In addition to the antennas, a simple transition from rectangular waveguide WR-10 to planar microstrip line on Rogers 3003? substrate has been designed based on probe coupling. For determination of the far-field radiation pattern of the antennas, we compare results from two different measurement methods to simulations. Both a far-field antenna measurement system and a planar near-field scanner with near-to-far-field transformation were used to determine the antenna diagrams. The fabricated antennas achieve a good matching and a good agreement between measured and simulated antenna diagrams. The results also show that the far-field scanner achieves more accurate measurement results with regard to simulations than the near-field scanner. The far-field antenna scanning system is built for metrological assessment and antenna calibration. The antennas are the first which were designed to be tested with the measurement system. 相似文献