Basic Rules for Indoor Anechoic Chamber Design

Author: Vince Rodriguez
Publication: IEEE Antennas & Propagation Magazine
Copyright Owner: IEEE - APS Magazine

Every year, many requests for proposals for an anechoic chamber are generated by companies and institutions that perform antenna measurements. The task of adequately specifying performance for an indoor anechoic chamber without driving unnecessary costs or specifying contradictory requirements requires insight that is not always available to the author of the specification. Although there are some articles and books that address anechoic chamber design [1]–[3], a concise compendium of reference information and rules of thumb on the subject of specifying ranges would be useful.

This article intends to be a helpful tool in that regard. It starts by recommending the proper type of range for different antenna types and frequencies of operation. Rules of thumb are provided to select the best approach for the required test or antenna type. Information is provided on the derivations needed for other ranges, such as compact ranges and near-field test facilities. Simple approximations are used for absorber performance to generate a series of charts that can be used as a guide to specify anechoic chamber performance and size. Company and institution facilities can then define the appropriate square footage necessary to house the required antenna range. This article intends to avoid some of the common contradictory requirements. Some of these contradictory requirements are not enough real estate to accommodate a chamber operating at low frequencies or levels that are not possible given available absorber technology.

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A Method for Gain over Temperature Measurements Using Two “Hot” Noise Sources

Authors: Vince Rodriguez and Charles Osborne

P Gain over Temperature (G/T) is an antenna parameter of importance in both satellite communications and radio-astronomy. Methods to measure G/T are discussed in the literature [1-3]. These methodologies usually call for measurements outdoors where the antenna under test (AUT) is pointed to the “empty” sky to get a “cold” noise temperature measurement; as required by the Y-factor measurement approach [4]. In reference [5], Kolesnikoff et al. present a method for measuring G/T in an anechoic chamber. In that approach, the chamber has to be maintained at 290 kelvin to achieve the “cold” reference temperature. In this paper, a new method is presented intended for the characterization of lower gain antennas, such as active elements of arrays. The new method does not require a cold temperature reference; thus alleviating the need for testing outside or maintaining a cold reference temperature in a chamber. The new method uses two separate “hot” sources. The two hot sources are created by using two separate noise diode sources of known excess noise ratios (ENR) or by one source and a known attenuation. The key is that the sources differ by a known amount. This paper builds upon the presented information in [2] providing more measured data using the recommended procedure.

Antenna Measurement Uncertainty Method for Measurements in Compact Antenna Test Ranges

Authors: Stephen Blalock and Jeffrey A. Fordham

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.

Computational Electromagnetic Modelling of Compact Antenna Test Range Quiet Zone Probing: A Comparison of Simulation Techniques

Authors: C.G. Parini, R. Dubrovka, S.F. Gregson

This paper extends the authors previous simulation study that predicted the quality of the pseudo plane wave of a single offset compact antenna test range (CATR). In this paper, the quiet-zone performance predictions are extended to rigorously incorporate the effects of probing the CATR quietzone using arbitrary but known field probes. This paper compares and contrasts results obtained using plane-wavespectrum and reaction integral based simulation techniques. This investigation leads to recommendations as to the optimal field probe choice and measurement uncertainties. The results of these new simulations are presented and discussed.

Modernising, Upgrading and Recommissioning the Indoor Antenna Range at Stellenbosch University

Authors: D. M. P. Smith, D. B. Davidson, A. Bester and J. Andriambeloson

This paper describes the upgrade to the indoor antenna range at Stellenbosch University. The previous measurement process relied upon obsolescent control equipment and undocumented software; it was critical that these be replaced. Now, the antenna range supports three measurement types using a commercial integrated measurement control system that provides support for high gain and low gain antennas over a wide frequency range. These are spherical near-field, planar near-field and conventional far-field measurements, with the potential to implement cylindrical near-field. The antenna range potentially supports operations from 1 GHz up to 26.5 GHz, though the currently available probes do not cover the full band. The main physical upgrade was performed during October 2014, though investigations had already begun in 2011, and some supplementary tasks were still ongoing at the time of writing. Several innovative commissioning tests have been undertaken, some of which are only possible with near-field metrology, and these are described in the paper.

Phased Array Antenna Calibration Measurement Techniques and Methods

Author: Kim Hassett

The adaptability of the phased array antenna makes it attractive for a variety of multi-beam applications. Previously, its use was limited mostly to military applications due to the large expenses associated with this type of antenna. In recent years, reduced costs have made phased array antennas viable for a variety of commercial applications. As this technology encroaches on new markets, with it comes the need to learn how to properly calibrate phased array antennas. To date, there have been numerous measurement techniques and methodologies developed for calibrating phased array antennas. This paper discusses those most commonly used in industry, and which could be easily and economically adapted for commercial applications.

Spherical Near-field Probe Fed Antenna Techniques for Accurate Millimeter Wave Measurements

Authors: F. Ferrero, S.F. Gregson, J. Lanteri, L. Brochier, Y. Benoit, C. Migliaccio, J-Y. Dauvignac

This paper present a specific set-up developed for antenna pattern measurements of probe-fed antenna with a 500mm AUT-probe distance. An example of Near-Field measurement is proposed and shows important errors on phase acquisition at 90GHz. Raw measurements are improved using a spherical correction based on laser-tracker structural data. Phase error and Near-field to Far Field transformation are strongly improved with this technique.

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