Article

A Brief History of the Development of the Near-field Measurement Technique at the Georgia Institute of Technology

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Abstract

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

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... The measured near field data were transformed to the far-field and compared with the measured far field radiation patterns. The work was continued later at Georgia Institute of Technology (GIT) [95], the National Bureau of Standards (NBS) [96] and the Technical University of Denmark (TUD) [97]. The benefits of near field measurement systems are: reduced size of the test range, well controlled indoor environment and cost efficiency compared to far field test ranges. ...
... 시작했다 [2] . 안테나뿐만 [4]~ [8] . ...
Article
This paper deals with the near-field to far-field calculation for far-field characteristics of antenna and electromagnetic compatibility(EMC) testing. Since the conventional EMC testing process is inefficient such as measurements of the wide band signals and mega structures, Stratton-Chu formula is used to predict the far-field emission by simple and direct process. The usefulness of Stratton-Chu formula is verified by comparing to the analytic solution of the uniform distribution aperture in free-space. In order to inspect the far-fields and to get the near-field values, full-wave simulation solver is utilized. Through the full-wave simulation about the patch antenna, calculated far-field results from Stratton-Chu formula are proven. The predicted magnitudes of the far-field are in error by less than 6 %.
Conference Paper
In this paper, a low-cost technique to measure the distance between a near-field probe and a planar antenna under test (AUT) is presented. This technique uses an unshielded printed ring resonator whose resonant frequency is shifted by varying its proximity to the AUT. The distance is derived from measured return loss of the ring resonator. The sensitivity of the resonant frequency with respect to the distance between the ring resonator and the AUT is more than 10 MHz/mm. This is compliant with the positioning accuracy requirements in near-field antenna measurements. Thus, it provides a convenient way to obtain the bound limit of z-positioning error. Such information can be used in AUT characterization based on the extraction of equivalent magnetic currents.
Article
A novel holographic near-field phase-less technique is presented. The measurement system is composed of the antenna under test, the reference antenna, the amplitude scanning measurement system, and the holographic reconstructed algorithm. The interference amplitude of the antenna under test with the reference antenna is measured by the amplitude scanning system. The complex near field of the antenna under test is reconstructed by a computer, where the measured interference is corrected by the multiplication with the virtual spherical reference wave and :then filtered in Fourier transformation domain (e.g., plane wave angular spectrum) or the back-projected image space. The reconstruction method is rigorous without traditional Fresnel approximation. The novel technique requires the amplitude on one measurement surface and the computer reconstructed algorithm, while the previous phase less technique depends on two measurement surfaces or extra hardware to provide synthesized-reference-wave. The novel measurement method and reconstruction algorithm could be used in many applications as for the planar near field measurement for example. Simulated results are presented to demonstrate the complex field retrieval method and near-field to far field transformation.
Article
A fast algorithm in frequency and time domain is presented for near field radiated by aperture antennas. The convolution formulation is earlier developed to relate the near field to the equivalent magnetic current sources on the aperture in frequency domain, which accelerates the near field's calculation via FFT, and Fourier transform pairs have been found on the basis of Plane wave spectrum (PWS) theory and convolution theorem. The algorithm in time domain can be obtained based on the method of frequency domain, which has been proved by the rigorous Electromagnetic theory associated with Fourier transform theory. Numerical results are presented for two antennas to verify the fast algorithm.
Article
An method was presented to measure bistatic RCS in anechoic chamber. The target was illuminated by compact antenna test range (CATR), and the scattered field was probed in near-field. The transformation from near-field to far-field (N2F) was analyzed by antennas coupling equation, plane wave synthesis and equivalence theorem. Sampling rate, maximum angle and taper function in N2F were formulated to analyze the measurement's performance. The sampling interval needs to be half wavelength, and undersample will worsen the maximum angle. The maximum angle's estimation was perfected using the synthetic aperture's projection. Far-field was determined by localized near-field approximatively, which can be concluded using stationary phase method. A taper function was applied to the near-field data that reduces the error of the scanning truncation. The method was validated through numerical example finally.
Article
This paper describes a wideband hologram-based CATR: which can be realized by linearly adjusting the feed location. The position needs to be adjusted for approximately compensating the wave front curve of the feed, which is proportional to the operating frequency. The theory can be conformed under the paraxial condition. For the acceptable quiet-zone field quality over a wide band, the large focal ratio is required. The idea is verified and the wideband performance of the quiet-zone is studied with the simulated and measured results at W band (95 GHz) and D band (170 GHz).
Conference Paper
A novel holographic near-field phaseless method is presented. The measurement system is composed of the amplitude scanning measurement system, the holographic reconstructed algorithm, the antenna under test (AUT) and the reference antenna. The interference amplitude of the AUT with the reference antenna is measured by the amplitude scanning system. The complex near field of the antenna under test is reconstructed by computer, where the measured interference field is corrected by the multiplication with the virtual spherical reference wave and then filtered in Fourier Transformation domain (e.g. Plane Wave Angular Spectrum) or the back-projected image space. The reconstruction method is rigorous without traditional Fresnel Approximation. The novel holographic phaseless measurement method can be used in many applications as for planar near field measurements for example. Measured and simulated results are presented to demonstrate the complex field retrieval method.
Chapter
Introduction Near-Field Measurement Theory Near-Field Measurement Practice Summary Acknowledgments Appendix A: Transmitting Probe, Receiving Test Antenna Appendix B: Special Probes Appendix C: Translated Probe Coefficients References
Conference Paper
The author elaborates on two of innovations that created the need for the Antenna Measurement Techniques Association (AMTA), the compact range and near-field range. On a far-field antenna range the source antenna must be located at a distance such that its spherical phase front is approximately planar over the aperture of the antenna whose pattern is being measured. For electrically large antennas this can result in very large distances. The attempt to reduce the required distance has lead to the development of compact and the near-field ranges. The first attempts at reducing the required distance was the use of lenses. Metal plate lenses, as well as dielectric lenses were investigated. Lenses proved to be only moderately successful
Article
A practical technique is developed to determine the electric and/or magnetic field on objects and sources inside a spherical measurement surface. The technique, known as spherical microwave holography (SMH), provides a nondestructive, nonintrusive method of point-by-point evaluation of antennas and radomes over their spatial extent. The resolution capability of SMH is developed and demonstrated by measurements. Resolution in SMH is only limited by the measurement system's capabilities. Dielectric and metallic obstacles on the surface of a radome are located and identified. Resolution as small as 0.33λ0 is demonstrated
Article
The ability to fully characterize a probe antenna using a near-field range is demonstrated subject to the conditions that two identical probes are available. A completely general three antenna approach, requiring no such assumptions, appears feasible. Some questions with respect to uniqueness of solution of the three antenna approach remain. Experimental results indicate that at wide angles (approx. 77 deg), considerably below the apparent geometric limit, the planar near-field approach suffers a notable loss of accuracy. Improvements in both hardware and software-techniques to increase the data handling ability of the near-field facility are described.
Article
An analytical technique was to compensate for the effects of the probe positioning errors on far field antenna patterns calculated from measured near field data. For the out of plane errors which cause the near field to be measured on a nonplanar surface, an integral equation relationship was developed between the electric field on the measurement surface and the near electric field on a planar surface. The equation was solved for the planar near field using an iterative technique called the vector projection algorithm. The inplane probe positioning errors caused the near field to be sampled nonuniformly. Uniformly spaced samples were recovered from the measured samples through the solution of a set of linear equations which relate the nonuniform samples of the near field to the Fourier series coefficients of the measured near field. Once the Fourier series coefficients were known, the periodic samples were recovered by the use of the discrete Fourier transform.
Article
An optimum probe criterion is defined by using the properties of the prolate spheroidal wave functions as they relate to the uncertainty principle and Fourier transform theory. It is shown that an optimum rectangular horn probe exists for the near-field measurement on a linearly polarized test antenna, and that its use produces the most accurate far-field predictions. A computer-aided procedure for the design of the optimum probe is described. It is found that the probe having the most directive far-field patter produces the most concentrated near-field response, the most accurate measured spectra, and the most accurate far-field patter predictions.
Conference Paper
This paper describes a 3 GHz experimental set-up for quasi real time tomography of biological media. Experiments on animal organs illustrate the main features of this imaging process.
Article
A new method is described of predicting an aerial radiation pattern from near-field measurements. The essence of this method is the expansion of the radiated field in terms of a series of radially expanding modes. The amplitude and phase of each mode are calculated by a Fourier analysis of the measured near field, and the radiation pattern is obtained as a Fourier series containing these measured amplitudes and phases. The theory is described in detail for a cylindrical (2-dimensional) aerial, and experimental results are presented to confirm the validity of this theory. The way in which the method may be extended to 3-dimensional aerials is explained. The method has the advantage that it can be applied anywhere in the near field
Article
A critical examination is made of the somewhat loose and incomplete statement that a polar diagram is the Fourier transform of an aperture distribution. By aperture distribution it is necessary to understand, in the two-dimensional case, distribution across the aperture of the component along the aperture plane of the electromagnetic field in the plane of propagation. Furthermore, the concept of the polar diagram has to be replaced by that of an angular spectrum, except in the common case when the aperture may be considered more or less limited in width, and the field is being evaluated at a point whose distance from the aperture is large compared with the width of the aperture (and the wavelength). For example, it is convenient for some purposes to regard the problem of diffraction of a plane wave by a semi-infinite plane screen, with a straight edge, as a problem about an aperture distribution in the plane of the screen. This is a case for which the concept of a polar diagram is not in general applicable, and has to be replaced by that of an angular spectrum. The field at all points in front of a plane aperture of any distribution may be regarded as arising from an aggregate of plane waves travelling in various directions. The amplitude and phase of the waves, as a function of their direction of travel, constitutes an angular spectrum, and this angular spectrum, appropriately expressed, is, without approximation, the Fourier transform of the aperture distribution. If the aperture distribution is of such a nature that the concept of the polar diagram is applicable at sufficiently great distances, then the polar diagram is equal to the angular spectrum. But the angular spectrum is a concept that is always applicable, whereas the polar diagram is one that is liable to be invalid (for example, in the Sommerfeld theory of propagation over a plane, imperfectly reflecting earth).
Article
Thesis--Georgia Institute of Technology, 1970.
Conference Paper
First Page of the Article
Conference Paper
This paper reports on the accuracy of far-field patterns determined from near-field measurements on a 499 element C-band phased array antenna. Hemispherical far-field patterns were determined from near-field measurements and principle plane cuts of these patterns were compared to the same cuts made on a farfield range. Comparisons are sheen for both the sum and azimuth difference patterns for three scan positions of the phased array.
Conference Paper
To demonstrate the speed, accuracy and ease with which near-field measurements can be made and far-field patterns can be predicted, Georgia Tech has recently automated its facility for near-field measurements and data processing for transformation from near-field to far-field patterns. A high speed mini-computer is utilized to control the near-field positioner, the data sampling and acquisition, the data transfer between the measurement facility and a Univac 1108 computer, and the plotting and display of the resulting far-field patterns. This paper describes the automated measurement and data processing system and identifies the special capabilities and advantages it provides.
Conference Paper
The cost of antenna pattern measurements for large phased arrays using conventional far-field ranges has been very high. The results of recent work at Georgia Tech have conclusively demonstrated that measurements in the near-field can yield far-field antenna patterns with an accuracy equal to that of a high quality far-field range. The objective of this work is to compare the cost of pattern measurements of large phased arrays by the conventional far-field method to the cost of equivalent near-field measurements. Costs were derived and documented for each measurement approach using a common basis for the estimation.
Conference Paper
Near-field measurements have been demonstrated to be a powerful tool for measurement of radar cross-section data. In theory, a complete description of the target, valid for both monostatic and bistatic configurations, can be obtained by illuminating the target with a number of plane waves, determining the plane wave spectrum of the scattered field for each illumination, and thus obtaining a general result by superposition. However, a vast amount of data is required for such a general description, even for a single radar frequency.
Article
A technique is presented for solution of the inverse problem of calculating the electric field on a planar surface from the electric field specified on a nearby surface. An integral equation is derived that relates two orthogonal components of the electric field on the nearby surface to the respective components of the plane wave spectrum of the planar electric field. The integral equation is solved by an iterative technique, and the planar near field is calculated by an inverse Fourier transform of the plane wave spectrum.
Article
A plane wave spectrum scattering analysis of the effects of a near-zone obstacle on the pattern performance of a directive antenna is discussed. The free-space azimuth monopulse antenna is characterized by its sum and difference mode plane wave spectra, and a computed plane wave scattering dyad is used to characterize the scattering by a metallic right circular cylinder when it is excited by the incident antenna spectra. An efficient computer algorithm has been developed to compute the far-zone scattered and total fields for the antenna/cylinder system. Extensive experimental data have been obtained, and the patterns calculated using the present analysis are in agreement with the measured data.
Article
The theory of near-field measurements for antenna practitioners is summarized, and the measurement procedures in three coordinate systems, namely rectangular, cylindrical, and spherical are outlined. Specific topics include probe characterization, measurement systems, data reduction, and attendant accuracies. The results of recent studies are also summarized, and some brief remarks on future applications of near-field measurements in the laboratory, the production line, and in field testing and evaluation conclude the paper.
Article
The general problem concerning the interaction of a probe antenna with the near field of an arbitrary antenna is considered. The application of the Lorentz reciprocity theorem to the problem of determining antenna characteristics, including the far-field pattern, is presented. The data required to correct for the directional effects of the probe, the effect of probe correction on the measured data, and the attendant mathematical computations in rectangular systems are described. Extensions to cylindrical and spherical systems are discussed.
Article
A technique for measuring the complex polarization ratio of an arbitrary antenna is presented. The technique requires the use of two antennas which are not circularly polarized but are otherwise arbitrary. Only reciprocity and linearity are assumed. Six amplitude and phase measurements are performed, two measurements for each pair of antennas. The complex polarization ratio of each antenna is then calculated from the six measurements. The specific details of the measurement technique are described and some measurement results presented.
Article
A new method is developed for determining the farfield pattern of an antenna from probe compensated near-field measurements over the surface of a right circular cylinder enclosing the antenna. The method is derived by first expanding both the field radiated by the antenna and the field radiated by the measurement probe, when it is used as a transmitter, into cylindrical wave expansions. The Lorentz reciprocity theorem is then used to solve for the field radiated by the antenna from the probe output voltage. It is shown rigorously that the antenna pattern can be determined independently of the characteristics of the measurement probe provided that certain calibration data are known. A method for determining these data from the measured far field radiated by the probe is described. It is shown that the necessary numerical integration can be performed with the fast Fourier transform algorithm. Experimental results are presented to validate the theory and to demonstrate its practicality from a measurement and computational viewpoint.
Article
A sample spacing criterion and a data minimization technique for measurements made over the surface of a plane in the near field of an antenna are presented. The sample spacing is shown to depend on the distance from the antenna to the measurement plane, and on the extent to which evanescent waves can be neglected. The near-field data minimization technique utilizes two-dimensional spatial filtering to effect a significant reduction in computational effort required to calculate selected portions of the far-field pattern. Far-field patterns of an X band antenna calculated from near-field measurements are presented and compared with those measured on a standard far-field range. The far-field calculations are repeated for several near-field sample spacings and for various post-filter sample rates.
Article
A procedure is presented for predicting by computer the radiation pattern of an antenna in the presence of a radome. The case of a horn antenna radiating through an actual aircraft radome is treated in detail, and a comparison is made between computed and measured antenna patterns. Good agreement between theory and experiment is noted.
Article
Digital computer predictions of aperture antenna patterns are shown to be far more complete, in terms of information concerning the field vectors over virtually unrestricted angular sectors and even at short distances, when vector rather than scalar diffraction theory is applied.
Article
In many cases, it is impractical or impossible to make antenna pattern measurements on a conventional far-field range; the distance to the radiating far field may be too long, it may be impractical to move the antenna from its operating environment to an antenna range, or the desired amount of pattern data may require too much time on a far-field range. For these and other reasons, it is often desirable or necessary to determine far-field antenna patterns from measurements made in the radiating near-field region; three basic techniques for accomplishing this have proven to be successful. In the first technique, the aperture phase and amplitude distributions are sampled by a scanning field probe, and then the measured distributions are transformed to the far field. In the second technique, a plane wave that is approximately uniform in amplitude is created by a feed and large reflector in the immediate vicinity of the test antenna. And in the third technique, the test antenna is focused within the radiating near-field region, patterns are measured at the reduced range, and then the antenna is refocused to infinity. Each of these techniques is discussed, and the various advantages and limitations of each technique are presented.
Probe compensated near-field measurements on a cylinder AP-21 A study of the accuracy of far-field patterns based on near-field measurements
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W. M. Leach and D. T. Paris, " Probe compensated near-field measurements on a cylinder, " IEEE Trans. Antennas Propagat., vol. AP-21, no. 4, pp. 435-445, July 1973. E. B. Joy, C. P. Burns, and G. P. Rodrigue, " A study of the accuracy of far-field patterns based on near-field measurements, " in Proc. 1973 IEEE/G-AP Int. Symp., Aug. 22-24, 1973, pp. 57-60.
Hexagonal sampling in near-lield measurements
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L. E. Corey and E. B. Joy. " Hexagonal sampling in near-lield measurements. " in Proc. Antenna Measurements Techniques As-SOC. 1984 Meeting, Oct. 2-4, 1984, pp. 3A4-1-3A4-15.
Development of a large near-field measurenient system for testing space-borne antennas
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W. P. Cook et al., " Development of a large near-field measurenient system for testing space-borne antennas. " in Proc. Antenna Measure-ment Techniques Assoc. 1986 Meeting, Sept. 23-25, 1986, pp. 35-38.
An outdoor UHF cylindrical wrfacc near-lield range
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K. W. Cozad and E. B. Joy. " An outdoor UHF cylindrical wrfacc near-lield range, " in Proc. Antenna Measurement Techniques Assoc. 1985 Meeting, Oct. 29-31, 1985, pp. 4 -4 -8.
Antenna pattern correction tor range reflections
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L. Jofre, E. B. Joy, and R. E. Wilson, " Antenna pattern correction tor range reflections, " in Proc. Antenna Measurement Techniques Assoc. 1987 Meeting, Sept. 28-Oct. 2, 1987, pp. 63-68.
Calculation of microwave antenna radiation systems, by the Fourier integral method The concept of an angular spectrum of plane waves, and its relation to that of polar diagram and aperture distribution
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Potential near-field measurement technique for determining near-zone and far-zone bistatic RCS
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Wilson, " Near-field measurement of radome anomalies, " in Proc. Antenna Measurement Techniques Assoc. 1987 Meeting, Sept. 28-B. J. Cown, C. E. Ryan, Jr.. and J. J. H. Wang, " Potential near-field measurement technique for determining near-zone and far-zone bistatic RCS. " in Proc. Antenna Measuremenl Techniaues Association Oct. 2, 1987, pp. 235-240.
Alternative Sampling tcchniqucs for more efficient planar near-field measurements
  • L E Corey
L. E. Corey and D. R. O'Neil, " Alternative Sampling tcchniqucs for more efficient planar near-field measurements, " in Proc. Antennu Measurements Techniques Assoc. 1985 Meeting, Oct. 29-31. 1985. pp. 7-1-7-10.
Antenna range for providing a plane wave for antenna measurements Digital computer analysis of aperture antennas Computer-aided radome analysis
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R. C. Johnson, " Antenna range for providing a plane wave for antenna measurements, " US Patent 3 302 205, Jan. 31, 1967. D. T. Paris, " Digital computer analysis of aperture antennas, " IEEE Trans. Antennas Propagat., vol. AP-16, pp. 262-264, Mar. 1968. D. T. Paris, " Computer-aided radome analysis ", IEEE Trans. Antennas Propagat., vol. AP-18, pp. 7-15, Jan. 1970.
Basic theory of probe compensated near-field measurements Applications of probe compensated near-field measurement Accuracy of hemispherical far-field patterns determined from near-field measurements Maximum near-field measurement error specification
  • D T Paris
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  • E B Joy
D. T. Paris, W. M. Leach, and E. B. Joy, " Basic theory of probe compensated near-field measurements, " IEEE Trans. Antennas Propagat., vol. AP-26, no. 3, pp. 373-379, May 1978. E. B. Joy, W. M. Leach, D. T. Paris, and G. P. Rodrigue, " Applications of probe compensated near-field measurement, " IEEE Trans. Antennas Propagat., vol. AP-26, no. 3, pp. 379-389, May 1978. E. B. Joy, C. P. Burns, G. P. Rodrigue, and E. C. Burdette, " Accuracy of hemispherical far-field patterns determined from near-field measurements, " in Proc. 1975 IEEE/G-AP Int. Symp., June 2-E. B. Joy, " Maximum near-field measurement error specification, " in Proc. 1977 IEEE/G-AP Int. Symp., June 20-24, 1977, pp. 390-393.
Electromagnetic near-field far-field transformations
  • F Jensen
An Cylindrical wave study
  • W M Leach Jr
Antenna range for providing a plane wave for antenna measurements
  • R C Johnson
Calculation of microwave antenna radiation systems, by the Fourier integral method
  • Clayton Jr
  • J S Hollis
Cylindrical near-field techniques with application to array antennas
  • V V Jory
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A simplified technique for probe position error compensation in planar surface near-field measurements
  • E B Joy
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Near-field measurement of radome anomalies
  • E B Joy
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  • R E Wilson
Monostatic near-field radar cross-section measurement
  • E B Joy
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  • B L Shirley