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Antennas and Propagation, IEEE Transactions on

Issue 6 • Date Jun 1988

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Displaying Results 1 - 21 of 21
  • Rapid near-field antenna testing via arrays of modulated scattering probes

    Publication Year: 1988 , Page(s): 804 - 814
    Cited by:  Papers (38)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1096 KB)  

    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 View full abstract»

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  • Application of spherical near-field measurements to microwave holographic diagnosis of antennas

    Publication Year: 1988 , Page(s): 869 - 878
    Cited by:  Papers (16)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (968 KB)  

    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 View full abstract»

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  • Error analysis techniques for planar near-field measurements

    Publication Year: 1988 , Page(s): 754 - 768
    Cited by:  Papers (86)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (992 KB)  

    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 View full abstract»

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  • Efficient and accurate method for calculating and representing power density in the near zone of microwave antennas

    Publication Year: 1988 , Page(s): 890 - 901
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    A method for computing and exhibiting Fresnel-region fields radiated by microwave antennas that uses plane-wave scattering matrix analysis is presented. Near-fields are calculated by numerically integrating the complex far-field antenna pattern. The predicted near fields are exhibited as relative power density contours lying in a longitudinal plane bisecting the antenna's aperture. With spatial-coordinate scaling, each set of contours becomes a function of the relative aperture distribution and the electrical size of the antenna. If the electrical diameter is much larger than any normalized transverse coordinate of interest, the contour set becomes invariant with respect to antenna size. The coordinate normalization can produce contours applicable to any antenna with the same relative aperture distribution, regardless of antenna size View full abstract»

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  • Effect of random errors in planar near-field measurement

    Publication Year: 1988 , Page(s): 769 - 773
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    Expressions that relate the signal-to-noise ratio in the near field to the signal-to-noise ratio in the far field are developed. The expressions are then used to predict errors in far-field patterns obtained from near-field data. A technique for measuring the noise in the calculated far-field pattern by calculating the spectrum in the evanescent region from a single-dimensional oversampled scan is also described View full abstract»

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  • Use of sampling expansions in near-field-far-field transformation: the cylindrical case

    Publication Year: 1988 , Page(s): 830 - 835
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    A modified sampling technique is applied to the reconstruction of the antenna far-field pattern from near-field measurements on a cylinder. It is shown that, if a proper phase factor is singled out from the tangential components of the measured electric field, the samples spacing along the axis of the measurement cylinder increases linearly with the cylinder radius. Thus, when this radius is substantially larger than the antenna's dimension, the sample's spacing can be much greater than the half-wavelength spacing commonly accepted as the maximum possible one, without losing the computational efficiency of the standard approach View full abstract»

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  • Surface accuracy measurement of a deployable mesh reflector by planar near-field scanning

    Publication Year: 1988 , Page(s): 879 - 883
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    Using a near-field antenna measurement facility, it is possible to simultaneously evaluate the surface accuracy of a reflector antenna as well as the far-field pattern of the antenna for a short time. The surface errors of a 2-m deployable mesh reflector for satellite use were measured by a planar near-field system. As a result, the influence of periodic structures, due to the antenna ribs, is clearly observed. Also, the surface accuracy obtained with the near field scanning technique coincides well with that obtained by an optical measurement technique View full abstract»

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  • Comparison of near-field range results

    Publication Year: 1988 , Page(s): 845 - 851
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    Comparisons of measurements on a contoured beam antenna carried out at five independent European test ranges are presented. They include a compact antenna test range, two cylindrical near-field test ranges, and two spherical near-field test ranges. The comparisons illustrate problems in the determination of gain values and cross polarization, while the agreement in the copolar patterns and the peak directivity is very good View full abstract»

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  • A brief history of near-field measurements of antennas at the National Bureau of Standards

    Publication Year: 1988 , Page(s): 727 - 733
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    The US National Bureau of Standards (NBS) played a pioneering role in the development of practical planar near-field antenna measurement techniques. A brief history is presented of that role, which began with theoretical studies to determine corrections for diffraction in a microwave measurement of the speed of light. NBS contributions to the development of nonplanar near-field measurement theory and practice are also described View full abstract»

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  • Improved polarization measurements using a modified three-antenna technique

    Publication Year: 1988 , Page(s): 852 - 854
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    An improved three-antenna measurement of polarization that greatly reduces the uncertainty due to phase measurement errors is described. This technique is used to calibrate polarization standards and probes used in near-field antenna measurements View full abstract»

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  • A brief history of the development of the near-field measurement technique at the Georgia Institute of Technology

    Publication Year: 1988 , Page(s): 740 - 745
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    The activity of the Georgia Institute of Technology in the development of the near-field measurement technique is reviewed. The work conducted during the years 1967-73 is given primary importance, and the major near-field developments in the 1973-80 time period are also described View full abstract»

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  • FFT applications to plane-polar near-field antenna measurements

    Publication Year: 1988 , Page(s): 781 - 791
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (852 KB)  

    The four-point bivariate Lagrange interpolation algorithm was applied to near-field antenna data measured in a plane-polar facility. The results were sufficiently accurate to permit the use of the FFT (fast Fourier transform) algorithm to calculate the far-field patterns of the antenna. Good agreement was obtained between the far-field patterns as calculated by the Jacobi-Bessel and the FFT algorithms. The significant advantage in using the FFT is in the calculation of the principal plane cuts, which may be made very quickly. Also, the application of the FFT algorithm directly to the near-field data was used to perform surface holographic diagnosis of a reflector antenna. The effects due to the focusing of the emergent beam from the reflector, as well as the effects of the information in the wide-angle regions, are shown. The use of the plane-polar near-field antenna test range has therefore been expanded to include these useful FFT applications View full abstract»

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  • An examination of the theory and practices of planar near-field measurement

    Publication Year: 1988 , Page(s): 746 - 753
    Cited by:  Papers (56)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    Using computer simulation, several fundamental issues in planar near-field measurement are examined. The results indicate that some of the prevailing views of practices regarding the evanescent modes, the sampling and filtering of data, and the selection of the location and directivity of the probe are incomplete or misleading. In particular, the merits of using smaller low-directivity probes in conjunction with a closer probe-to-antenna distance have been found to be unduly overlooked View full abstract»

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  • Near-field probe used as a diagnostic tool to locate defective elements in an array antenna

    Publication Year: 1988 , Page(s): 884 - 889
    Cited by:  Papers (39)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    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 View full abstract»

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  • Extrapolation of near-field RCS measurements to the far zone

    Publication Year: 1988 , Page(s): 822 - 829
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (676 KB)  

    An algorithmic procedure for extrapolating near-field radar cross-section (RCS) measurements to the far zone has been derived, coded, and experimentally validated. The deviation of the extrapolation algorithm uses an optical model to estimate the surface currents induced on the scattering body by the incident field, and a specially weighted version of the Fourier transform to calculate the near-field scattering amplitudes associated with such surface currents. The extrapolation entails three steps. First, near-field measurements of the scattered electric and/or magnetic field are used to infer the monostatic vector potential. Next, the inverse Fourier transform of the inferred vector potential is multiplied by a special weighting function to estimate an equivalent obliquity factor. Finally, the far-field scattering pattern is estimated by taking the Fourier transform of the reweighted obliquity factor. This extrapolation procedure has been validated using anechoic-chamber data taken on a right-circular aluminium cylinder 25 λ high and 2.5 λ in radius at near-field range of 19% of 2 D2/λ where D is the nominal target diameter and λ the radiation wavelength. The extrapolated RCS pattern for this target was compared with an analytical estimate of its far-zone pattern and good amplitude and phase agreement was observed over a 20° cone of scattering angles View full abstract»

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

    Publication Year: 1988 , Page(s): 774 - 780
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    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 View full abstract»

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  • Near-field qualification methodology

    Publication Year: 1988 , Page(s): 836 - 844
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (888 KB)  

    A methodology that is a combination of analysis, computer simulation, component certification, self-tests, and comparison tests is presented for the accuracy qualification of near-field antenna measurement ranges. The analysis uses closed-form equations to establish upper-bound far-field determination errors due to near-field measurement errors. Computer simulation is used to model the specific near-field measurement errors associated with the near-field measurement system components. The closed-form equations and computer simulations are used to form a near-field error budget for each of the near-field measurement system components. A near-field system component certification is undertaken to measure the near-field measurement system component error and establish that they are within the error budget View full abstract»

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  • Spherical near-field scanning at the Technical University of Denmark

    Publication Year: 1988 , Page(s): 734 - 739
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    The early work (1969-79) on spherical near-field antenna measurements at the Technical University of Denmark (TUD) is outlined. A spherical near-field transmission formula is described and the first probe-corrected spherical near-field measurements are discussed. The TUD-ESA (European Space Agency) joint effort on spherical near-field testing is also described View full abstract»

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  • Theory and practice for a spherical-scan near-field antenna range

    Publication Year: 1988 , Page(s): 815 - 821
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    A spherical-scan near-field antenna range is described. The procedure for real-time data processing is outlined. Relations for the number of data points, largest aspect angle measured, and data acquisition and processing times as a function of the antenna diameter-to-wavelength ratio and the measurement distance are given. Experimental results are presented for an antenna enclosed by a minimum sphere having a diameter of 240 wavelengths. All the equations for the spherical wave analysis, probe correction, and radial transformation are provided in appendices in numerically convenient form without the use of any special functions View full abstract»

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  • Accurate determination of planar near-field correction parameters for linearly polarized probes

    Publication Year: 1988 , Page(s): 855 - 868
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1020 KB)  

    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 View full abstract»

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  • Gain and power parameter measurements using planar near-field techniques

    Publication Year: 1988 , Page(s): 792 - 803
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    Equations are derived and measurement techniques described for obtaining gain, effective radiated power, and saturating flux density using planar near-field measurements. These are compared with conventional far-field techniques, and a number of parallels are evident. These give insight to the theory and help to identify the critical measurement parameters. Application of the techniques to the Intelsat VI satellite is described View full abstract»

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IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

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Editor-in-Chief                                                 Kwok W. Leung