AMTA Paper Archive

 

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Far Field
An Effective Antenna Modelling For the NF-FF Transformation with Planar Wide-Mesh Scanning
C. Gennarelli,F. D'Agostino, F. Ferrara, G. Riccio, R. Guerriero, November 2005
ABSTRACT A fast and accurate technique is proposed in this work for the far field evaluation from a nonredundant number of voltage data collected by using the planar wide-mesh scanning (PWMS). It relies on the nonredundant sam­pling representations of the electromagnetic field and on the optimal sampling interpolation expansions of central type. By using a very flexible source modelling, which fits very well a lot of actual antennas, a new sampling technique is developed to recover the plane-rectangular data from the knowledge of the PWMS ones. It must be stressed that the so developed near-field–far-field transfor­mation requires a number of data remarkably lower than that needed by the standard plane-rectangular scanning. Some numerical tests, assessing the accuracy of the technique and its stability with respect to random errors affecting the data, are reported.
An Effective Antenna Modelling For the NF-FF Transformation with Planar Wide-Mesh Scanning
C. Gennarelli,F. D'Agostino, F. Ferrara, G. Riccio, R. Guerriero, November 2005
ABSTRACT A fast and accurate technique is proposed in this work for the far field evaluation from a nonredundant number of voltage data collected by using the planar wide-mesh scanning (PWMS). It relies on the nonredundant sam­pling representations of the electromagnetic field and on the optimal sampling interpolation expansions of central type. By using a very flexible source modelling, which fits very well a lot of actual antennas, a new sampling technique is developed to recover the plane-rectangular data from the knowledge of the PWMS ones. It must be stressed that the so developed near-field–far-field transfor­mation requires a number of data remarkably lower than that needed by the standard plane-rectangular scanning. Some numerical tests, assessing the accuracy of the technique and its stability with respect to random errors affecting the data, are reported.
Theoretical Basis and Applications of Near-Field Spiral Scannings
C. Gennarelli,C. Rizzo, C. Savarese, F. D'Agostino, G. Riccio, November 2005
ABSTRACT A unified theory of near-field spiral scans is proposed in this work by introducing a sampling representation of the radiated electromagnetic field on a rotational surface from the knowledge of a nonredundant number of its samples on a spiral wrapping the surface. The obtained results are general, since they are valid for spirals wrapping on quite arbitrary rotational surfaces, and can be directly applied to the pattern reconstruction via near-field–far-field transfor­mation techniques. Some numerical tests, assessing the accuracy of the technique and its stability with respect to random errors affecting the data, are reported with ref­erence to the case of the helicoidal scan.
An Original Microwave Near-Field / Far-Field Spherical Setup: Application to Antennas and Scattered Fields Measurements
P. Sabouroux,C. Eyraud, J.M. Geffrin, November 2005
At the Institut Fresnel in Marseille (France), we created an original experimental setup in order to test antennas and carry out scattering measurements in both monostatic and bistatic configurations. The main advantage of this setup is, of course, the multipurpose feature. Two main mechanical systems are installed in a large anechoic chamber. The first system is a spherical positioning setup which allows measurements of antennas and scattered fields for both bi-dimensional (2D) and three-dimensional (3D) targets. This setup consists of two carriages moving on a circular vertical arch and a third carriage which follows a circular path on a horizontal plane. A transmitter and a receiver can be fixed on any of these three carriages. A fourth rotating stage in the center of the spherical setup fixes the angular position of the antenna under test or of the scattering target. The second system is a far-field positioner which allows the measurement antenna patterns and RCS. To illustrate our activities with this original setup, we first show measurements of a metamaterial antenna prototype and then some results of scattered fields obtained on 2D and 3D targets used in studies of electromagnetic direct and inverse problems.
An Open-Boundary Quad-Ridged Guide Horn Antenna for Use as a Source in Antenna Pattern Measurement Anechoic Chambers
V. Rodriguez, November 2005
The present paper introduces a new antenna design to be used in anechoic chambers. When measuring 3D patterns the receiving antenna in the anechoic chamber must be able to sense the two orthogonal components of the field that exist in the far field. This can be accomplished by mechanically rotating the source horn in the chamber. A better and faster approach is to use a dual polarized antenna and electronically switch between polarizations. This new design is a broadband (2-18GHz) antenna with dual polarization. The antenna is a ridged guide horn. The novel part is that the sides have been omitted. Numerical analysis and measurements show that this open-sided or open-boundary horn provides a better and more stable pattern behavior for the entire band of operation as well as good directivity for its compact design. The radiation and input parameters of the antenna are analyzed in this paper for the novel design as well as for some of the early prototypes to show some of the ill effects of bounded quadridge horn designs for broadband applications. Mechanically the antenna is built so that it can be mounted onto the shield of an anechoic room without compromising the shield integrity of the chamber.
3-D Antenna Measurement System - Low Gain Antenna Measurements and CTIA OTA Testing
D. Gray,J. Soong, November 2005
ABSTRACT We are in the era of wireless communications and devices. The antennas that enable these technologies are electrically small and can be challenging to test and analyze. Yet, the industry is becoming more standardized, and so too are the tests and certifications being adopted to validate these antennas. These antennas must undergo “antenna measurements” to characterize such information as far-field patterns and gain. Additionally, hand-held devices, such as cell phones, must satisfy requirements of the Over-the-Air (OTA) performance tests as specified by the Cellular Telecommunication and Internet Association (CTIA). These tests require a measurement system that can accurately collect data on a spherical surface enclosing the AUT. This system also has to provide the appropriate data analysis capabilities and has to be constructed from dielectric materials to minimize reflections.
An Analysis of The Accuracy of Efficiency Measurements of Handset Antennas Using Far-field Radiation Patterns
I. Kadri,R. Thorpe, T, Palmer, November 2005
Radiation efficiency is an inherent property of an antenna that relates the net power accepted by an antenna to the total radiated power. It is especially useful for handset antennas where the radiation patterns are often of less use for comparing competing antennas. Radiation patterns though not as useful for direct comparisons, still provide one method by which efficiency can be calculated. To accurately calculate the efficiency from patterns, it becomes necessary to obtain multiple pattern measurements (cuts). A larger number of cuts whilst yielding more accurate efficiency results, significantly increase measurement time. Thus an antenna designer is often forced to trade off accuracy against measurement time since both quick and accurate measurements are desired. The focus of this paper is to quantify this trade off, in order to provide guidelines on the number of pattern measurements required for accurate efficiency results. Simulated and measured far-field radiation patterns are used and various numbers of cuts are utilized to quantify the loss in accuracy with a reduced number of cuts. The techniques outlined are geared primarily towards cellular handset antennas.
PID - 316 - A Hemi-Spherical Near-Field System for Automotive Antenna Testing
P. Betjes,D. Janse van Rensburg, D. Pototzki, November 2005
A hemi-spherical near-field test system with to be considered. This type of test system offers a added far-field capability is described. The facility has practical solution to the test problem in that combined been constructed for the characterization of automotive motion of a probe antenna and the object under test, antennas. The test system consists of an 11m tall allows for spherical data acquisition covering one half of dielectric gantry, a 6.5m diameter in-ground turntable and the spherical surface. The configuration also allowsa 28m-diameter radome enclosure. Special software integration of a conducting ground plane as well as a required to compensate for the reflectivity in the facility radome enclosure for weather protection andand the hemi-spherical truncation was developed and confidentiality. forms an integral part of this test system. The characteristics of this facility are described in this paper The characteristics of this newly developed and measured data is presented. facility are described in the following section of this paper.
Near-Field to Far-Field Characterization Using Amplitude-Only Data
F. Las-Heras,T. Sarkar, November 2006
In this paper we present a direct optimization procedure which utilizes phase-less electric field data over arbitrary surfaces for the reconstruction of an equivalent magnetic current density that represents the radiating structure or an antenna under test. Once the equivalent magnetic current density is determined, the electric field at any point can be calculated. Numerical results using experimental data are presented to illustrate the applicability of this approach for non-planar near field to far field transformation as well as in antenna diagnostics.
Near-Field to Far-Field Characterization Using Amplitude-Only Data
F. Las-Heras,T. Sarkar, November 2006
In this paper we present a direct optimization procedure which utilizes phase-less electric field data over arbitrary surfaces for the reconstruction of an equivalent magnetic current density that represents the radiating structure or an antenna under test. Once the equivalent magnetic current density is determined, the electric field at any point can be calculated. Numerical results using experimental data are presented to illustrate the applicability of this approach for non-planar near field to far field transformation as well as in antenna diagnostics.
APATS: Antenna Pattern Analytical Tool Set
B. Voetberg,C. Salisbury, J. Moore, November 2006
The Air Force Research Laboratory (AFRL), RF Technology Branch at the Rome Research Site, Rome NY provides a capability of far field antenna testing on full scale aircraft. A computer program, APATS – Antenna Pattern Analytical Tool Set, was developed in conjunction with the Information Systems Research Branch to provide a better way to visualize and understand the antenna pattern data taken during testing. The program is written in Java and relies on JView, developed by the Information Systems Research Branch, to process and display the 3D, three-dimensional, elements of the program.
Deriving Far-Field Performance Parameters from Near-Field Amplitude Measurements of Wireless Devices
P Iversen,S. Gaymay, November 2006
The CTIA (The Wireless Association – www.ctia.org) were the first to publish a widely accepted test plan for antenna performance testing of “live” mobile phones[1]. The test plan describes the use of phantom heads and involves recording transmitted power and receiver sensitivity information over a full sphere to derive parameters such as Total Radiated Power (TRP) and Total Integrated Sensitivity (TIS). The test plan, has until now, assumed that testing is performed in the far-field at test distances greater than 2D2/.. For typical mobile phone frequency and device test diameters (assumed 300mm in the CTIA test plan), this has not been a constraint. However, as such testing evolves to include the various versions of IEEE 802.11 combined with new devices such as larger laptops and other consumer electronics, a far-field test requirement would lead to very large test facilities. Using experiments and rigorous simulations, this paper will show that for the commonly accepted performance criteria, the far-field requirement is unnecessarily strict. A minimum distance requirement based on the geometry and probe pattern is proposed which will ensure that the performance parameters (TRP, TIS, and others) are obtained with insignificant loss of accuracy.
A New Look at Phaseless Planar Near Field Measurements: Limitations, Simulations, Measurements, and a Hybrid Solution
F. Razavi,Y. Rahmat-Samii, November 2006
In this paper we have revisited the phase retrieval problem for planar near-field antenna measurements. It will be shown that the complexity of retrieval procedures is function of not only the independency of different sets of measurements but also the characteristics of the antenna under test (AUT). Features of antenna like its beam direction will have profound effect on the success of phase reconstruction algorithms. The failure of a well known phase retrieval method, Iterative Fourier Transform (IFT), is investigated for a case where the antenna has a scanned beam. It is found that this is due to the non-judiciary choice of the initial guess. To alleviate the deficiency of the IFT a simple but effective initial guess is sought by Differential Evolutionary Algorithm (DEA). DEA tries to find the best initial phase guess which minimizes an error criterion. Subsequently this best guess will be fed to the phase retrieval IFT routine for further phase refinements. Having done this the far-field can subsequently be constructed. The improvement in the phase reconstruction algorithm is examined, through a series of simulations and measurements.
On the Impact of Non-Rectangular Two Dimensional Near-field Filter Functions in Planar Near-Field Antenna Measurements
D. Janse van Rensburg, November 2006
In this paper a circular planar near-field scan region is considered as an alternative to the commonly used rectangular boundary. It is shown how the selection of this alternative boundary can reduce test time and also to what extent the alternative truncation boundary will affect far-field accuracy. It is also shown how well known single dimensional filter functions can be applied over a two-dimensional region of test and how these attenuate the truncation effect. The boundary and filter functions are applied to measured data sets, acquisition time reduction is demonstrated and the impact on far-field radiation pattern integrity in assessed.
Comparative Validation Methodology for a Combined Cylindrical and Spherical Near-Field Measurement System
U. Shemer,C. Tse Tong, November 2006
DSO National Laboratories has commissioned a high performance combined near-field and far-field antenna test facility in 2004. This facility supports highly accurate measurement of a wide range of antenna types over 1 – 18 GHz. This combined NF-FF system allows for planar, cylindrical and spherical near-field measurements, as well as far-field measurements. The combined near-field and far-field test facility has undergone meticulous validations making use of a TICRA calibrated “Golden Antenna” (GA). A detailed account of the cylindrical and spherical near-field comparative validation methodology and the test results are the subject of this article. The validation results for planar near-field (PNF), cylindrical near-field (CNF), spherical near-field (SNF) and far-field measurements have clearly shown that the system fulfils all the performance requirements without the use of a calibrated probe. Although dedicated near-field test facilities are generally thought to provide superior measurement accuracies, it will be shown in this article that a well-designed combined NF-FF test facility can deliver highly accurate results without the use of a calibrated probe. This makes the combined NF-FF system a viable and cost-effective antenna measurement solution, without compromising on measurement accuracies.
Reduction of Truncation Error in the Near-Field-Far-Field Transformation with Planar Spiral Scanning
F. D'Agostino,C. Gennarelli, C. Rizzo, C. Savarese, F. Ferrara, R. Guerriero, November 2006
ABSTRACT An elaborate and effective strategy for estimating the samples external to the measurement region in the planar spiral scanning is developed in this paper. It relies on the nonredundant sampling representations of the electromagnetic field and on the optimal sam­pling interpolation expansions of central type and uses the singular value decomposition method for extrapolating the outside samples. It is so possible to reduce the inevitable truncation error affecting the near-field reconstruction, thus giving rise to a more accurate far-field prediction. Numerical examples as­sess the effectiveness of the proposed technique.
A Partial Rotation Formulation of the Circular Near Field-to-Far Field Transformation (CNFFFT)
S. Rice,I. LaHaie, November 2006
For many years now, General Dynamics has described the development, characterization, and performance of an image-based circular near-field-to-far-field transformation (CNFFFT) for predicting far-field radar cross-section (RCS) from near-field measurements collected on a circular path around the target. In this paper, we consider the CNFFFT algorithm as an azimuthal filtering process and develop a formulation capable of transforming data that is not measured over a full 360º. Such a formulation has applications in measurement scenarios where collection of a complete rotation is not practical. As part of the development, we provide guidelines for the near-field data support required to achieve a desired accuracy in the sub-360º CNFFFT result. Numerical simulations are provided to demonstrate that the results of this partial-rotation formulation are consistent with the full-circle CNFFFT results presented in past papers.
A Partial Rotation Formulation of the Circular Near Field-to-Far Field Transformation (CNFFFT)
S. Rice,I. LaHaie, November 2006
For many years now, General Dynamics has described the development, characterization, and performance of an image-based circular near-field-to-far-field transformation (CNFFFT) for predicting far-field radar cross-section (RCS) from near-field measurements collected on a circular path around the target. In this paper, we consider the CNFFFT algorithm as an azimuthal filtering process and develop a formulation capable of transforming data that is not measured over a full 360º. Such a formulation has applications in measurement scenarios where collection of a complete rotation is not practical. As part of the development, we provide guidelines for the near-field data support required to achieve a desired accuracy in the sub-360º CNFFFT result. Numerical simulations are provided to demonstrate that the results of this partial-rotation formulation are consistent with the full-circle CNFFFT results presented in past papers.
Development of a Hemispherical Near Field Range with a Realistic Ground - Part 3
E. Walton,C. Buxton, F. Paynter, J. Snow, T-H. Lee, November 2006
This is part three of a series of talks on the development of a new type of near field antenna range. The range is designed to measure the VHF and UHF antenna characteristics of a vehicle over a realistic ground. This means that the spherical symmetry has been lost and the classical spherical mode expansions are not appropriate. We have previously demonstrated a plane wave synthesis approach to the far field transformation, including the lossy dielectric half-space representing the ground. This third yearly presentation will discuss the compensation needed for realistic probe antenna, probe arm and turntable imperfections. Results for actual experimental measurement data with sample space and probe antenna time dispersion compensation will be shown. Comparisons with the theoretical far field computations and the spherical mode expansion results will be included.
Spherical Near Field Radome Test Facility for Nose-Mounted Radomes of Commercial Traffic Aircraft
M. Boumans,J. Wagner, November 2006
Typically radome tests are performed on outdoor far field ranges or compact ranges. ORBIT/FR has designed, build and qualified a unique spherical near-field radome test facility for the nose-mounted radomes of commercial traffic aircraft for the so-called “after repair” tests according to the international standard RTCA/DO-213, as well as the aircraft manufacturers Component Maintenance Manuals. The facility is extremely compact (chamber size 5.7 m x 5.2 m x 3.2 + 0.7 m, L x W x H), can handle radomes as small as used on the Canadair and as large as used on the Airbus-380 and can be installed directly in the repair workshop for such radomes. The tests performed are transmission efficiency and side lobe level increase. The system is completely automated, so that a workshop technician can operate the facility. Utmost attention has been paid to operational aspects and both operator and equipment safety. After the measurements are done, a test report is fully automatically generated according to RTCA requirements and classifications. The facility is equipped to test all standard Airbus, Boeing, Canadair and Dash nose radomes.


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