Closed-Loop Real-Time PNF Position Compensation with a Tracking Laser

Authors: Scott T. McBride, Steven R. Nichols
Publication: EuCAP 2015
Copyright Owner: IEEE

If a planar near-field (PNF) scanner is large and there is insufficient temperature regulation in the chamber to keep ordinary thermal expansion/contraction from causing unacceptable position errors, then consideration must be given to compensation techniques that can adjust for the changes. Thermal expansion/contraction will affect almost everything in the chamber including the floor, the scanner structure, the encoder or position tapes, the AUT support, and the mount for any extra instrument(s) used to measure and correct for position error. Since the temperature will generally cycle several times during a lengthy acquisition, error-correction solutions must account for the dynamic nature of the temperature effects.

This paper describes a new automated tracking-laser compensation subsystem that has been designed and developed for very large horizontal PNF systems. The subsystem is active during the acquisition to account for both static and dynamic errors and compensates for those errors in all three dimensions. The compensation involves both open-loop corrections for repeatable errors with high spatial frequency and closed-loop corrections for dynamic errors with low spatial frequency. To close the loop, laser data are measured at a user-defined interval between scans and each scan that follows the laser measurements is fully compensated. The laser measurements are fully automated with no user interaction required during the acquisition.

The challenges, goals, and assumptions for this development are listed, the high-level implementation concept is described, and resulting measured data are presented.

You have requested a Reprint of an IEEE Paper

Copyright 2015 IEEE. Reprinted from EuCAP 2015 Conference.

This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of NSI-MI Technologies' products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org.

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Compact Range Quiet Zone Modelling: Quantitative Assessment using a Variety of Electromagnetic Simulation Methods

Authors: C.G. Parini, R. Dubrovka, S.F. Gregson
Publication: The Loughborough Antennas and Propagation Conference, 2015.
Copyright Owner: IEEE

This paper presents the results of a recent computational electromagnetic (CEM) simulation campaign for a single offset reflector CATR, where a number of models employing different field propagation methods were compared and contrasted both qualitatively and quantitatively using objective, non-local statistical image classification techniques.

The challenges, goals, and assumptions for this development are listed, the high-level implementation concept is described, and resulting measured data are presented.

You have requested a Reprint of an IEEE Paper

Copyright 2015 IEEE. Reprinted from The Loughborough Antennas and Propagation Conference, 2015.

This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of NSI-MI Technologies' products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org.

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Effect of Higher Order Modes in Standard Spherical Near-Field Probe Correction

Authors: A.C. Newell, S.F. Gregson
Publication: AMTA 2015
Copyright Owner: NSI-MI Technologies

Within the standard scheme for probe-corrected spherical data-processing, it has been found that for an efficient computational implementation it is necessary to restrict the characteristics of the probe pattern such that it contains only azimuthal modes for which μ = ±1 [1, 2, 3]. This first-order pattern restriction does not however extend to placing a limit on the polar index mode content and therefore leaves the directivity of the probe unconstrained. Clearly, when using this widely utilized approach, errors will be present within the calculated probe-corrected test antenna spherical mode coefficients for cases where the probe is considered to have purely modes for which μ = ±1 and where the probe actually exhibits higher order mode structure. A number of analysis [4, 5, 6, 7, 8] and simulations [9, 10, 11, 12] can be found documented within the open literature that estimate the effect of using a probe with higher order modes. The following study is a further attempt to develop guidelines for the azimuthal and polar properties of the probe pattern and the measurement configuration that can be utilized to reduce the effect of higher order spherical modes to acceptable levels. Included in this study are the cases when an Open Ended Waveguide (OEWG) is simulated at a series of measurement distances, a Quad Ridged Horn Probe (QRHP) with very large higher order modes is also simulated, the AUT is offset from the origin of the measurement sphere and the AUT is simulated with its main beam along the equator rather than along the pole. These new simulation cases provide additional guidelines when selecting a probe for spherical near-field measurements and answer some questions that have been raised about generalizing past results.

Estimating Measurement Uncertainties in Compact Range Antenna Measurements

Authors: Stephen Blalock & Jeffrey A. Fordham
Publication: AMTA 2015
Copyright Owner: NSI-MI Technologies

Methods for determining the uncertainty in antenna measurements have been previously developed and presented. The IEEE has published IEEE 1720-2012 that formalizes a methodology for uncertainty analysis of near-field antenna measurements. In contrast, approaches to uncertainty analysis for antenna measurements on a compact range are not covered as well in the literature. A review and discussion of the terms that affect gain and sidelobe uncertainty are presented as a framework for assessing the uncertainty in compact range antenna measurements including effects of the non-ideal properties of the incident plane wave. An example uncertainty analysis is presented.

Factors Limiting the Upper Frequency of mm-Wave Spherical Near-field Test Systems

Author: Daniël Janse van Rensburg
Publication: EuCAP 2015
Copyright Owner: IEEE

Antennas operating at mm-wave frequencies have led to the development of spherical near-field test systems that have to function at higher frequencies than before. This paper addresses some of the factors limiting the upper frequency bound of spherical near-field test systems in terms of what is practical with current technology. This includes mechanical positioning systems, RF sub-systems and the spherical near-field sampling requirements. Correction techniques that have been developed to enhance the performance of such measurement systems are also presented.

You have requested a Reprint of an IEEE Paper

Copyright 2015 IEEE. Reprinted from 2015 EuCAP Conference.

This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of NSI-MI Technologies' products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieee.org.

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Millimeter-wave Performance of Broadband Aperture Antenna on Laminates

Authors: Rashaunda Henderson, Richard Pierce, Supreetha Aroor, Joel Arzola, Christopher Miller, Harini Kumar, Thethnin Ei, Andrew Blanchard, Dave Fooshe, Bert Schluper, Dan Swan, Carlos Morales
Publication: AMTA 2015
Copyright Owner: NSI-MI Technologies

This paper summarizes the design, fabrication and characterization of a coplanar waveguide fed modified aperture bowtie antenna operating in the 60 to 90 GHz range. Modifications to the bowtie edges extend the bandwidth up to 40% without increasing radiator area. The antenna was initially designed and measured in the 3-8 GHz frequency band and then frequency scaled to 60-90 GHz. The millimeter wave antenna is implemented on FR408 (r=3.65) and a multilayer laminate. Both substrates can be used in millimeter-wave system design where efficient antennas are needed. Return loss measurements of the antennas are made on a Cascade probe station. The results agree well with simulations in ANSYS HFSS. Until recently, only simulated radiation patterns were available illustrating broadside gain of 5 to 7 dB for these antennas. With the acquisition of a spherical scanner, near-field measurements have been taken of the three antennas from 67 to 110 GHz. The broadside radiation pattern results are compared with simulation. The NSI 700S-360 spherical near-field measurement system used in conjunction with an Agilent network analyzer, GGB Picoprobes and Cascade manipulator allow for on-wafer measurements of the antenna under test.

Predicting the Performance of a Very Large, Wideband Rolled-Edge Reflector

Authors: Anil Tellakula, William R. Griffin, and Scott T. McBride
Publication: AMTA 2015
Copyright Owner: NSI-MI Technologies

Achieving a very large quiet zone across a wide frequency band in a compact range system requires a physically large reflector with a suitable surface accuracy. The size of the required reflector dictates attention to several important processes such as how to manufacture the desired surface across a large area and the practicality of transportation and installation. This inevitably leads to the segmentation of the reflector into multiple panels; which must be fabricated, installed, and aligned to each other to conform to the required geometry. Performance predictions must take into account not only the surface accuracy of the individual panels, but also their alignment errors.

This paper presents the design approach taken on a recent project for a compact range system utilizing a blended rolled-edge reflector that produces a 5 meter quiet zone across a frequency range of 350 MHz to 40 GHz. It discusses the physical segmentation strategy, the fabrication methodology, the intermediate qualification of panels, the panel alignment technique, and the laser-based metrology methodology employed. Performance analysis approach and results will be presented for the geometry as conceived, and then for the realized panelized reflector as machined and aligned.

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