Galen H. Koepke

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

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.

Radiated emissions and immunity of microstrip transmission lines: theory and reverberation chamber measurements

The increasing complexity of electronic systems has introduced an increased potential for electromagnetic interference (EMI) between electronic systems. We analyze the radiation from a microstrip transmission line and calculate the total radiated power by numerical integration. Reverberation chamber methods for measuring radiated emissions and immunity are reviewed and applied to three microstrip configurations. Measurements from 200 to 2000 MHz are compared with theory, and excellent agreement is obtained for two configurations that minimize feed cable and finite ground plane effects. Emissions measurements are found to be more accurate than immunity measurements because the impedance mismatch of the receiving antenna cancels when the ratio of the microstrip and reference radiated power measurements is taken. The use of two different receiving antenna locations for emissions measurements illustrates good field uniformity within the 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.

Radio-Wave Propagation Into Large Building Structures—Part 1: CW Signal Attenuation and Variability

We report on our investigation into radio communications problems faced by emergency responders in disaster situations. A fundamental challenge to communications into and out of large buildings is the strong attenuation of radio signals caused by losses and scattering in the building materials and structure. Another challenge is the large signal variability that occurs throughout these large structures. We designed experiments in various large building structures in an effort to quantify continuous wave (CW) radio-signal attenuation and variability throughout twelve large structures. We carried radio frequency transmitters throughout these structures and placed receiving systems outside the structures. The transmitters were tuned to frequencies near public safety, cell phone bands, as well as ISM and wireless LAN bands. This report summarizes the experiments, performed in twelve large building structures. We describe the experiments, detail the measurement system, show primary results of the data we collected, and discuss some of the interesting propagation effects we observed.

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.

Radio-Wave Propagation Into Large Building Structures—Part 2: Characterization of Multipath

We report on measurements that characterize multipath conditions that affect broadband wireless communications in building penetration scenarios. Measurements carried out in various large structures quantify both radio-signal attenuation and distortion (multipath) in the radio propagation channel. Our study includes measurements of the complex, wideband channel transfer function and bandpass measurements of a 20 MHz-wide, digitally modulated signal. From these, we derive the more compact metrics of time delay spread, total received power and error vector magnitude that summarize channel characteristics with a single number. We describe the experimental set-up and the measurement results for data collected in representative structures. Finally, we discuss how the combination of propagation metrics may be used to classify different propagation channel types appropriate for public-safety applications.

Measurements in Harsh RF Propagation Environments to Support Performance Evaluation of Wireless Sensor Networks

Purpose – The purpose of this paper is to describe common methods for evaluating the performance of wireless devices such as wireless sensors in harsh radio environments.Design/methodology/approach – The paper describes how measurements of real‐world propagation environments can be used to support the evaluation process, then presents representative measurement data from multipath environments where sensor networks are likely to be deployed: a fixed‐infrastructure, process‐control environment (here an oil refinery), and a heavy industrial environment (here an automotive assembly plant).Findings – Results on the characterization of multipath in the propagation channel are summarized and how these results may be used in the performance evaluation of sensor networks is discussed.Originality/value – The paper describes measurement results from environments where little open‐literature data exists on point‐to‐point propagation, specifically high‐multipath environments. These highly reflective scenarios can pre...