2019 Technical Papers

Proposed Changes and Updates on IEEE Std 1128 - Recommended Practice on Absorber Evaluation

Authors: Zhong Chen, Vince Rodriguez
Publication: AMTA 2019
Copyright Owner: NSI-MI Technologies

Abstract — The last published version of the IEEE Std 1128 is the 1998 edition. It is titled “Recommended Practice for RF Absorber Evaluation in the Range of 30 MHz to 5 GHz”. Over the years, the document has been used widely for absorber evaluations in electromagnetic compatibility (EMC) applications as well as in antenna and microwave measurement applications. Besides the obvious frequency range which needs to be expanded to satisfy today’s applications, several areas are in need of an update. The proposed document will change the upper frequency limit to 40 GHz (with provisions in the document to potentially extend above 40 GHz based on test methods). Measurement uncertainties were not discussed in the IEEE Std. 1128 – 1998. In the new edition, measurement instrumentation and test methods are expected to be updated with guidance on estimating measurement uncertainties. In the proposed document, a section on absorber evaluations for high power applications is planned, and fire properties and test methods will be included.

A Robotic Near-Field Antenna Test System Relying on Non-Canonical Transformation Techniques

Authors: Daniël Janse van Rensburg, Brett Walkenhorst, Quang Ton & John Demas
Publication: AMTA 2019
Copyright Owner: NSI-MI Technologies

A robotic near-field antenna measurement system allowing for acquisition over non-canonical measurement surfaces is presented. The robot consists of a six-axis robotic arm and a seventh axis rotary positioner and the created acquisition surface is parametrically reconfigurable. The near-field to far-field transformation required is also described. The success of the technique is demonstrated through measured results, compared to canonical measurement data.

A Review of the Changes and Additions to the Antenna Measurement Standard IEEE Std 149

Authors: Vince Rodriguez, Jeff Fordham, Lars Foged
Publication: AMTA 2019
Copyright Owner: NSI-MI Technologies

The IEEE Standard 149, Standard Test Procedures for Antennas, has not been revised since 1979. Over the years the Standard was reaffirmed, that is, its validity was re-established by the IEEE APS Standards Committee, without any changes. Recently however, the IEEE Standards Association stopped the practice of reaffirming standards. This change in policy by the IEEE has been the “medicine” that this Standard needed. A working group was organized and a project authorization request (PAR) was approved by IEEE for the document to be updated. In this paper, the expected changes to the document are described and commented. The main change is to convert the Standard to a recommended practice document. Additionally, some new techniques to measure antennas, such as the use of reverberation chambers for efficiency measurements and more information on compact ranges, is discussed. Other topics inserted are more guidance on indoor ranges and an updated section on instrumentation. Most importantly, a discussion on uncertainty is included. The result will be a very useful document for those designing and evaluating antenna test facilities, and those performing the antenna measurements.

A Methodology for Instantaneous Polarization Measurements Using a Calibrated Dual-Polarized Probe

Authors: Brett T. Walkenhorst, Steve Nichols
Publication: AMTA 2019
Copyright Owner: NSI-MI Technologies

Accurately measuring the polarization of an antenna is a topic that has garnered much interest over many years. Methods abound including phase-referenced measurements using two orthogonal polarizations, phase-less measurements using two or three pairs of orthogonal polarizations, spinning linear probe measurements, and the rigorous three-antenna polarization method. In spite of the many publications on the topic, polarization measurements are very challenging and can easily lead to confusion, particularly in accurately determining the sense of polarization.

In this paper, we describe a method of accurately and rapidly measuring the polarization of an antenna with the aid of a multi-channel measurement receiver and a dual-polarized probe. The method acquires phase-referenced measurements of two orthogonal polarizations. To enable such measurements, we describe a methodology for calibrating the probe. We also describe a tool for automating the polarization measurement and display of the polarization state. By automating the process, it is hoped that the common challenges and confusions associated with polarization measurements may be largely obviated.

Advances in Characterizing Complex Frequency Responses of Frequency Converting Payloads in Planar Near-Field Test Ranges

Authors: Patrick Pelland, Daniël Janse van Rensburg, Edwin Barry
Publication: EuCAP 2019
Copyright Owner: EurAAP

This paper provides an overview of a planar near-field test methodology for measuring typical system level characteristics of transceiver payloads. Measuring parameters such antenna gain, equivalent isotropic radiated power, saturating flux density, group delay and channel frequency response is the objective. We describe how transfer functions are derived for the antennas in question, allowing one to compensate for the fact that measurements are being performed in the near-field of both uplink and downlink antennas. Practical implementation aspects like near-field probe selection, probe positioning and RF sub-system modification are addressed. We also present a concept simulated payload, since this is critical to system verification and facility-to-facility comparison.

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A Review of the CW-Ambient Technique for Measuring G/T in a Planar Near-Field Antenna Range

Authors: Ryan T. Cutshall, Brett T. Walkenhorst, Justin Dobbins, Jacob Freking, Bruce Williams
Publication: AMTA 2019
Copyright Owner: Raytheon

Techniques for measuring G/T have been previously presented at AMTA; however, there are very few papers that discuss how to measure G/T in a near-field antenna range. One recent paper discussed such a method and gave a brief description within the larger context of satellite payload testing [1]. The paper’s treatment of G/T was necessarily brief and gives rise to several questions in relation to the proposed method. Other papers that treated this topic required the antenna aperture to be separable from the back-end electronics, which may not be possible in all cases [2-3]. In this paper, we discuss in great detail a slightly modified version of the G/T measurement method presented in [1]. A signal and noise power diagram is presented that can be useful for understanding how system signal-to-noise ratio (SNR) relates to G/T, and a few common misconceptions concerning the topic of G/T are addressed. The CW-Ambient technique for computing G/T of a Unit Under Test (UUT) from measurements in a planar near-field system is described in detail, and a list of assumptions inherent to the CW-Ambient technique is presented. Finally, the validity of the CW-Ambient technique is assessed by analyzing measured data collected from a separable UUT.