Foreword

The authors of this book have done me the honor of entrusting me with this foreword, and above all of mentioning my activities in the field of the mode-stirred chambers at the Academic Naval Institute of Naples (currently Parthenope University of Naples). Somehow, I have on this matter the benefit of age, which allows me to give some little-known indications about a period of time when there were very few people studying reverberation chambers. It is particularly pleasant to see that nowadays this subject finds a place in numerous sessions, during conferences and other international meetings.

As is so often the case, activity comes from a very specific and almost always anecdotal motivation. This was the case for reverberation chambers. At the beginning of the 1970s, microwaves started to spread in Italy and there were some worries about them. In 1974-1975, we were consulted about the methods of measuring electromagnetic radiation. At this time, we were working on the extraction principle of the signals drowned out by noise, as well as on the possibility of using this technique in the field of electromagnetic waves. The idea to make electromagnetic radiation become incoherent via agitation of the walls or, more easily, with the rotation of the metal surfaces was then almost natural.

At the same time, in the United States, we were studying the inefficiency of the MIL-STD norms, for the evaluation of shielding effectiveness. The method used a compact resonant cavity, where it was possible to make the tuning frequency vary, thanks to the use of metal inserts, diving more or less strongly in the cavity. The technique consisting of using the same method, in order to no longer obtain the resonance but to carry out an average evaluation on several positions of these metal inserts, was also natural. The idea then was to no longer use a cavity, but a shielded chamber instead. The team was formed of McDonnel Douglas (Saint-Louis), the US Navy Dahlgren Laboratory, and Boulder NBS (currently NIST).

The first article with an international impact (1976) brought American and English researchers to visit us in Naples, and at a meeting of information exchange (1977) at Litton, Minneapolis, officiated by D. Robertson (GeorgiaTech). We confronted the two points of view, that differ on the mode stirring question, whether it was done step-by-step or continuously. This debate is still relevant nowadays, because mode stirring requires a specific sampling of the measurements. I will not dwell on this question as it is well discussed in this book. Let us thus come back to the development of the first works on this subject.

In 1979, I installed the first mode-stirred chamber at NBS/NIST, by modifying an old shielded chamber. But we should not forget that some chambers were already in operation in the United States at McDonnel, US Navy Dahlgren, Litton and in some other places. The basic principles were all already determined, but we had to convince the experts of the strong potential of this method. At the beginning of the 1980s, NBS/NIST made a big effort and M. Crawford developed a systematic experimental activity, covering a wide range of frequencies. The results of these experiments were published in the Technical Notes of NBS, and nowadays mark the transit from a pioneer activity to a real emergence of the subject. The first already considered statistic formulations will improve, the practical use will spread, and the international standards will take it into account. At the same time, the subject was being developed in Europe. After the pioneer work done in Italy, we could find the study of reverberation chambers in France, the United Kingdom, the Netherlands and then in Germany. Continuing this description would certainly be beyond the scope of this foreword, because this book by B. Démoulin and P. Besnier does not limit itself to the study of the current state of the matter, but also presents the main episodes of its development.

In any case, we can find two lines of study: electromagnetic field statistics, often limited to an analysis evaluation without support of physical modeling, and the practical use, above all in reference to the international standards. Despite the fact that it is an activity that started more than 30 years ago, we find very few things about it in the literature. We can find chapters in the general texts of electromagnetism and of electromagnetic compatibility, and, to my knowledge, only one book recently and exclusively devoted to the subject, but its remains quite abstract. Evidently, we can try to summarize a quite voluminous bibliography. However, this is a difficult exercise, especially because of the progressive nature of the research results accumulated over time. This book by B. Démoulin and P. Besnier is the perfect aid to help us, being very complete from the theoretical point of view, as well as from the practical point of view. Above all, it aims at extracting from the numerous bibliographical entries, the essential principles necessary for the use of reverberation chambers. The measurement methods resulting from reverberation chambers are indeed simple in principle, and the use of reverberation chambers is not difficult. This book manages to convince us of that fact, without however forgetting to give the reader the basic operating principles and the restrictions of use. The authors did not yield to the temptation of exploiting their scientific activity in the field, although it is ample and of a high level. They position themselves with readers who have a basic knowledge in electromagnetism, in order to give complete knowledge of what underlies the functioning of reverberation chambers. Consequently, readers are progressively brought to the level of the state of the art: this is a very difficult exercise that the authors have achieved perfectly, thanks to their knowledge and their activity in the domain.

I have mostly talked about the use of the book, and not its qualities. There are good reasons for that fact. First, this book is perfect and complete, but I particularly appreciated it from the point of view of the mission it has taken upon itself. This book satisfies the need for a single reference, at a homogeneous level, that could be used by anybody who does not have the chance to follow the development of the exploitation method of mode stirred chambers. This will encourage more frequent use of this test system and the development of new applications, a subject that the book will also discusses. We have to be grateful to the authors for wanting to write a book that aids understanding and better situates the subject in the literature, without flaunting their knowledge or the originality of their activity, which is spread throughout the book. This is a sacrifice for the researcher, especially if we consider that the research groups of Lille and Rennes have given and still give the important contribution of burning issues to the theoretical and experimental exploitation of mode stirred chambers.

Professor Paolo Corona

Parthenope University of Naples

July 2011