Reflection Suppression in Cylindrical Near-Field Antenna Measurement Systems - Cylindrical MARS

Authors: Stuart Gregson, Allen Newell, Greg Hindman
Publication: AMTA 2009
Copyright Owner: NSI-MI Technologies

Reflections in antenna test ranges can often be the largest source of measurement error within the error budget of a given facility. Previously, a technique named Mathematical Absorber Reflection Suppression (MARS) has been used with considerable success in reducing range multi-path effects in spherical near-field antenna measurements. Whilst the technique presented herein is also a general purpose measurement and postprocessing technique; uniquely, this technique is applicable to cylindrical near-field antenna test ranges. Here, the postprocessing involves the analysis of the cylindrical mode spectrum of the measured field data which is then combined with a filtering process to suppress undesirable scattered signals.

This paper provides an introduction to the measurement technique and a description of the novel near-field to farfield transform algorithm before presenting preliminary results of actual range measurements. These results illustrate the success of the technique by showing a circa 10 to 20 dB reduction in spectral reflections (i.e. a reduction in the scattering from a known scatterer within the measurement environment) which is comparable to the degree of improvement attained with the pre-existing, comparable, spherical MARS technique.

Sub-millimeter Wave Planar Near-field Antenna Testing

Authors: Daniёl Janse van Rensburg, Greg Hindman
Publication: EuCAP 2009
Copyright Owner: IEEE

This paper provides an overview of planar near-field antenna test systems developed for sub-millimeter wave testing. Special techniques that have been developed to overcome technical restrictions that usually limit performance at very high RF frequencies are presented. Aspects like thermal structural change, RF cable phase instability, scanner planarity and probe translation during polarization rotation are addressed. These methods have been implemented and validated on systems up to 660 GHz and 950 GHz. These cases have lead to the development of low cost commercial test systems, making antenna testing in the V and W-bands (40 – 110 GHz) cost effective.

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Copyright 2009 IEEE. Reprinted from EuCAP 2009 Conference.

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The Effect of the Absorber Collar on Open Ended Waveguide Probes

Authors: Allen Newell, Stuart Gregson
Publication: AMTA 2009
Copyright Owner: NSI-MI Technologies

This paper describes measurements performed at the National Physical Laboratory (NPL) and Near Field Systems Inc (NSI) on Open Ended Waveguide (OEWG) probes that are typically used for near-field measurements. The effect of the size and location of the absorber collar placed behind the probe was studied. It was found that for some configurations, the absorber collar could cause noticeable ripples in the far-field patterns of the probe and this in turn could affect the probe correction process when the probe was used in near-field measurements. General guidelines were developed to select an absorber configuration that would have minimal effect on the patterns, polarization and gain of the probes.


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