Comparison of Cylindrical and Spherical Mathematical Absorber Reflection Suppression

Authors: S.F. Gregson, A.C. Newell, G.E. Hindman, M.J. Carey
Publication: Reprinted from Loughborough Conference on Antennas and Propagation, 2010
Copyright Owner: IEEE

Reflections in antenna test ranges can often constitute the largest single term within the error budget of a given facility. For some time, a frequency domain measurement and postprocessing technique named Mathematical Absorber Reflection Suppression (MARS) has been successfully used to reduce range multi-path effects within spherical near-field and far-field antenna measurement systems. More recently, a related technique has been developed for use with cylindrical near-field antenna measurement systems. This paper provides an introduction to the measurement techniques and a description of the novel near-field to far-field transform algorithms before presenting preliminary results of actual range measurements of a low gain antenna taken using a combination spherical / cylindrical system that was installed within a partially anechoic chamber. These results illustrate the success of the techniques which are found to provide comparable improvements yielding far-field patterns that are in encouraging agreement despite every step within the data acquisition, transformation and postprocessing chain being different thereby providing further compelling evidence of the success of the MARS technique.

You have requested a Reprint of an IET Paper

Copyright 2010 IEEE. Reprinted from Loughborough Conference on Antennas and Propagation, 2010.

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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Embracing Complexity: MIMO Over-the-Air Testing with the Reverberation Chamber

Authors: Derek Skousen, Charlie Orlenius
Publication: Microwave Journal, August 6, 2010
Copyright Owner: Microwave Journal

This article describes a repeatable reference environment for over-the-air (OTA) testing of multiple input multiple output (MIMO) devices and why the reverberation chamber is uniquely suited to provide insight into MIMO device performance. The importance of reference environments and the characteristics of the reverberation chamber in the context of 4G wireless systems are reviewed. Statistically based measurements are described and compared with the line-of-sight solutions implemented in an anechoic chamber environment.

You have requested a Reprint of a Microwave Journal Paper

Microwave Journal Copyright ©2010. Reprinted from August 2010 issue.

This material is posted here with permission of the Microwave Journal. Such permission of the Microwave Journal does not in any way imply Microwave Journal 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 Microwave Journal by writing to mwj@mwjournal.com.

By choosing to view this document, you agree to all provisions of the copyright laws protecting it.


Evaluation of LO Power Leveling Techniques Used for Remote Mixing

Author: Sudarshan ‘CV’ Chakravarty
Publication: AMTA 2010
Copyright Owner: NSI-MI Technologies

Operating microwave receivers with remote mixers in a system requires the LO power to be flat over broadband frequencies. In large systems, this is difficult to attain due to long RF cables. Most systems require significant engineering to ensure the LO power level to the mixer is adequate. To help understand the problem, commonly used techniques have been evaluated while recommending a particular approach.

Operating over a small fundamental frequency range with harmonic mixing has the advantage of lower RF cable insertion loss but results in high mixer conversion loss. Using negative slope equalizers and amplifiers, RF cable slope and attenuation can be sufficiently combated. However, this requires extensive system engineering and customization to match cable losses, thereby making it expensive. The approach is also designed to only work with a certain set of RF cables.

A more viable approach includes independently controlling the attenuators and amplifiers for the signal and reference channels which can be configured to provide optimal LO power to the respective mixer. A simple setup file configures components in each channel to adapt to any set of RF cables. Positive experimental results of implementing this technique in different configurations are presented.

Extension of the Mathematical Absorber Reflection Suppression Technique to the Planar Near-Field Geometry

Authors: Stuart Gregson, Allen Newell, Greg Hindman, Michael Carey
Publication: AMTA 2010
Copyright Owner: NSI-MI Technologies

Obtaining a quantitative accuracy qualification is one of the primary concerns for any measurement technique. This is especially true for the case of near-field antenna measurements as these techniques consist of a significant degree of mathematical analysis. When undertaking this sort of examination, room scattering is typically found to be one of the most significant contributors to the overall error budget. Previously, a technique named Mathematical Absorber Reflection Suppression (MARS) has been used with considerable success in quantifying and subsequently suppressing range multi-path effects in first spherical and then, cylindrical near-field antenna measurement systems. This paper details a recent advance that, for the first time, enables the MARS technique to be successfully deployed to correct data taken using planar near-field antenna measurement systems. This paper provides an overview of the measurement and novel data transformation and post-processing chain. Preliminary results of computational electromagnetic simulation and actual range measurements are presented and discussed that illustrate the success of the technique.

High Accuracy Spherical Near-Field Measurements On a Stationary Antenna

Authors: Greg Hindman, Hulean Tyler
Publication: AMTA 2010
Copyright Owner: NSI-MI Technologies

Most conventional spherical near-field scanning systems require the antenna under test to rotate in one or two axes. This paper will describe a novel rolling arch near-field scanner that transports a microwave probe over a hyper-hemispherical surface in front of the antenna. This unique scanning system allows the antenna to remain stationary and is very useful for cases where motion of the antenna is undesirable, due to its sensitivity to gravitational forces, need for convenient access, or special control lines or cooling equipment. This allows testing of stationary antennas over wide angles with accuracies and speeds that historically were only available from planar near-field systems.

The probe is precisely positioned in space by a high precision structure augmented by dynamic motion compensation. The scanner can complete a hyperhemispherical multi-beam, multi-frequency antenna measurement set of up to eight feet in diameter in less than one hour.

The design challenges and chosen techniques for addressing these challenges will be reviewed and summarized in the paper.

Millimeter Wave Near-Field Antenna Testing

Author: Daniël Janse van Rensburg
Publication: (MPD) Microwave Product Digest, August 2010 Issue
Copyright Owner: NSI-MI Technologies

This paper provides an overview of antenna test systems that operate in the millimeter and sub-millimeter wave bands. Techniques that have been developed to overcome technical restrictions that usually limit performance at very high RF frequencies are presented. Aspects such as 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 test systems operating from 50 GHz up to 950 GHz.

Mitigating Interference on an Outdoor Range

Author: Roger Dygert
Publication: AMTA 2010
Copyright Owner: NSI-MI Technologies

Making measurements on an outdoor range can be challenging for many reasons, including test article size, weather, and undesired electromagnetic effects. The challenges this paper addresses are those associated with the dense spectral environment in which measurements must often be made. Signals from external emitters must be prevented from causing interference with the measurement, and the outdoor range must not cause interference with other nearby systems. These criteria oppose each other in that if range transmit power is increased sufficiently to limit the effects of interference on the measurement, the range may cause interference to other systems. If low power is used in the range to avoid causing interference to others, the external emitter may make measurements on the range difficult to impossible. This paper demonstrates how, by using a sensitive receiver with high selectivity, one can make measurements right in the band of the interferer. By changing how the signal is processed, measurement capability is enhanced.

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