John M. Ladbury

On the Use of Reverberation Chambers to Simulate a Rician Radio Environment for the Testing of Wireless Devices

With the proliferation of wireless devices in recent years, there is a growing need to test the operation and functionality of these various devices in different multipath environments, ranging from line-of-sight environment to a pure Rayleigh environment. In this paper we discuss how a reverberation chamber can be used to simulate a controllable Rician radio environment for the testing of a wireless device. We show that by varying the characteristics of the reverberation chamber and/or the antenna configurations in the chamber, any desired Rician K-factor can be obtained. Expressions for the desired K-factor as a function of the chamber and antenna characteristics will be presented. Experimental results are presented to illustrate the validity of these expressions, to show how the reverberation chamber can be used to simulate different multipath environments, and to show the realization of a controlled K-factor test facility. We present both a one-antenna and a two-antenna test configuration approach

Spatial-correlation functions of fields and energy density in a reverberation chamber

A plane-wave integral representation is used to derive spatial-correlation functions for the complex electric and magnetic field components, and the results agree with previously published results derived by volume averaging of a mode sum. Results are also presented for the correlation functions of squared electric and magnetic field components and electric, magnetic, and total energy densities. The theory for the spatial correlation function of the squared transverse electric field is shown to agree well with published measurements of the power received by transverse monopole antennas.

Reverberation-chamber research-then and now: a review of early work and comparison with current understanding

The heart of this paper is an English translation (from the original Italian) of an early (1976) paper. Interspersed with this translation is an original critical review (printed in normal text) of the paper. Much of the current theory, models, and analysis techniques associated with reverberation chambers can be directly traced to the original paper by Corona and Latmiral (1976). The paper also contained a number of interesting suggestions and applications that would make excellent research topics. The original paper is considered a classic, even though (prior to this publication), an English translation is difficult to locate and reference. Publication of this translation will help establish some of the origins of reverberation-chamber concepts that we now take for granted.

Directivity of the test device in EMC measurements

We present a statistical theory for estimating the directive characteristics of unintentional emitters based and the electrical size of the device. We compare this theory to directivity derived from pattern measurements in an anechoic chamber. We also use this theory to predict the maximum radiated fields based on total radiated power measurements in the reverberation chamber.

Reverberation chamber relationships: corrections and improvements or three wrongs can (almost) make a right

We correct a number of errors that have crept into the reverberation-chamber literature over the past several years. These include errors in equations and interpretation of data. Wherever possible, we identify the causes and implications of these errors. We pay particular attention to the so-called 4/spl pi//8/spl pi/ controversy where measurements appear to disagree with theory by approximately 3 dB. We also compare the power received by an antenna in an anechoic chamber and a reverberation chamber and give approximate equivalence relationships for comparison of such facilities.

Verification of fields applied to an EUT in a reverberation chamber using statistical theory

Among the significant characteristics of the electromagnetic environment in a reverberation chamber are isotropy and homogeneity. These characteristics permit robust immunity testing without moving the equipment-under-test or the field generating antenna. However, the statistical nature of the electromagnetic environment gives rise to questions about the ability to predict the test fields at the equipment-under-test. The first issue is the ability to predict and/or establish the maximum test field. The second issue is the ability to predict the field at the equipment-undertest based on a measurement at the monitor antenna/probe location which is in the working volume but remote from the equipment-under-test. This paper extends the comparison of experimental data and the maximum to mean ratio predicted from statistical theory. The paper also compares measured data to theoretical predictions for the maximum field at arbitrary locations within a reverberation chamber based on a measurement of the mean field at the monitor location.

Measuring the Shielding Effectiveness of Small Enclosures/Cavities with a Reverberation Chamber

For various applications, there is a growing need to determine the shielding effectiveness (SE) of physically small (but electrically large) enclosures or cavities. In this paper, we present a reverberation chamber technique for measuring the SE of such enclosures. We present data from four different reverberation chamber approaches obtained from various enclosure configurations. These four different sets of measurements are used to validate the proposed approach.

Emission and immunity standards: replacing field-at-a-distance measurements with total-radiated-power measurements

This paper examines the use of total radiated power measurements, combined with theory-based directivity estimates, to generate accurate estimates for the maximum radiation and reception from a device. This approach may be a useful alternative to present test methods for emission and immunity as frequencies above 1GHz become necessary for EMC standards. Radiation-pattern data for theory-based estimates, Monte Carlo simulations of an arbitrary device, and measurements on a sample device are presented, and good data agreement is demonstrated.

Examining the true effectiveness of loading a reverberation chamber: How to get your chamber consistently loaded

In this paper we explore how placing the same amount of absorber in different locations within a reverberation chamber can have different loading effects. This difference can have a significant impact on measurement reproducibility, both for measurements in the same chamber and measurements between chambers (i.e., round robin style testing). We begin by discussing some of the theories behind this and show some experimental results from different absorber placements in a reverberation chamber. We conclude with some suggestions to ensure absorber is placed consistently.

Electrically short dipoles with a nonlinear load, a revisited analysis

We reexamine the characteristics of electrically short dipoles with nonlinear loads and, specifically, the early work of Motohisa Kanda (1980, 1983). Although this topic has been examined in great detail in the past, some inconsistencies between numerical and analytical results are apparent, and these have not been previously addressed. We show that these inconsistencies were due to only periodic sampling of the analytic solution, and an insufficient number of iterations in the numerical solutions, and we give corrected results. Additionally, some of the more significant analytical results, which were once thought to be impractical due to their complexity, are numerically implemented. We also show that a simple approximation accurately describes the behavior of these electrically short dipoles over a wide range of frequency and amplitude.