Bien que souvent présentés comme des configurations atypiques, la classe des milieux diffusifs représente une grande partie des milieux dans lesquels se propagent des ondes aussi bien électromagnétiques qu'acoustiques. Les grandes cavités étant capables de bien approcher ces mêmes caractéristiques, elles sont largement utilisées dans un contexte métrologique, afin d'émuler un grand nombre de configurations pratiques et d'évaluer certaines propriétés de dispositifs électroniques, acoustiques et optiques. Nous nous intéressons à la modélisation statistique de la propagation d'ondes dans les grandes cavités. La pratique courante de modéliser les champs dans une cavité comme diffus est d'abord analysée, afin de montrer comment cette hypothèse n'est pas réaliste en basse fréquence, et les conséquences qui en découlent. L'importance du recouvrement modal et sa nature aléatoire sont discutées, montrant comment l'hypothèse diffusive ne peut pas être décrite comme une propriété certaine. Dans un deuxième temps nous étudions les applications du retournement temporel aux grandes cavités, ce qui nous amène à l'introduction d'une technique généralisée capable de reproduire des fronts d'ondes cohérents dans un environnement diffusif, typiquement regardé comme uniquement capable de supporter une propagation aléatoire.

This thesis covers the development of the Reverberation Chamber as a measurement tool for cell phone tests in electronic production. It also covers the development of the Scattered Field Chamber as a measurement tool for simulations of real propagation environments. The first part is a more ”general knowledge about Reverberation Chambers”-part that covers some important phenomena like unstirred power and position dependence that might occour in a small Reverberation Chamber used for cell phone tests. Knowing how to deal with these phenomenas, give the possibility to use the chamber as a measurement tool for production tests even though it is too complex for a simple test of the antenna function. The second part shows how to alter some important propagation parameters inside the chamber to fit some real world propagation environments. The 3D plane wave distribution, the polarization and the amplitude statistics of the plane waves are all altered with simple techniques that are implementable all together. A small, shielded anechoic box with apertures is used to control 3D plane wave distribution and polarization. Antennas that introduce unstirred power in the chamber are used to control the statistics.

Ce travail porte sur les techniques de mesure des champs en cavité électromagnétique et plus précisément en chambre réverbérante. En raison de la perturbation induite sur la distribution du champ au sein d'une cavité résonante par la présence d'un objet, les techniques de mesure de champ classiques utilisant une antenne souffrent d'une précision limitée. Par conséquent, nous proposons une nouvelle technique de mesure de la distribution du champ électrique basée sur la théorie des perturbations. Elle consiste à mesurer les variations de la fréquence de résonance de la cavité pour chaque position de l'élément perturbateur introduit dans la cavité, puis à en déduire la variation de l'amplitude du champ électrique. Le choix de la forme de l'objet perturbateur, de ses dimensions et de son matériau constitutif est effectué à partir des résultats des simulations et des mesures dans un cas canonique, de façon à adapter le banc de mesure au cas étudié. Cette technique de mesure est ensuite appliquée avec succès au cas d'une chambre réverbérante équipée d'un brasseur de modes, ainsi qu'à des mesures de champ à l'intérieur d'un boitier inséré dans la cavité. Cette approche a permis, via un post-traitement basé sur l'utilisation de l'algorithme MUSIC, de déterminer avec une grande précision les directions d'arrivée des champs dans la chambre réverbérante / This work deals with field measurement techniques in large electromagnetic enclosures namely reverberation chambers. Due to the perturbation of the field distribution within a resonant cavity due to the presence of an introduced object, conventional field measurement techniques employing an antenna suffer from a limited accuracy. Therefore we propose a new measurement technique of the electric field distribution based on the perturbation theory; it consists of a measure of the cavity resonant frequency variation when displacing a small perturbing object within the cavity, and leads to the electric field distribution. The choice of the perturbing object shape, dimension and material is discussed with the help of simulation and measurement results in a canonical case in order to adapt the measurement setup to the studied case. This technique is then successfully employed in a reverberation chamber equipped with a mode stirrer, as well as to measure the field within a metallic box placed in the cavity. Using a post-processing based on MUSIC algorithm, this approach has permitted to determine accurately the field directions-of-arrival in the reverberation chamber

This theoretical diploma thesis deals with room acoustics and the closely related issue of reverberation. Part of the work is a drafting of acoustic modifications of the church based on manual calculation, which was further modified in a specialized software Odeon Room Acoustics Program. For the surrounding buildings of the church was created a study of the noise in a program Hluk+ in order to assess what will be the noise impact of this new building on its surroundings. On the basis of specialization was created several proposals for the design of the church. The approximate proposal of the double-plated dome, a system of drainage of the coupling neck, and the ways the anchor of the hard large-format window glazing. The result of the work is suitable design of acoustic adjustments and improvement of the listening qualities for the future construction of this church.

Die Elektromagnetische Verträglichkeit (EMV) betrachtet die Fähigkeit eines elektrischen Gerätes, in seiner elektromagnetischen Umgebung störungsfrei zu funktionieren, ohne diese dabei unzulässig zu stören. Zur Prüfung der Elektromagnetischen Verträglichkeit werden verschiedene Messumgebungen verwendet. Die Messung der strahlungsgebundenen Störfestigkeit und Störaussendung kann zum Beispiel in einer Modenverwirbelungskammer (MVK) erfolgen. Bei der Störfestigkeitsmessung wird der Prüfling einem externen Prüffeld ausgesetzt und untersucht, ob dieser die definierten Kriterien für einen störungsfreien Betrieb erfüllt. Für das Prüffeld muss vor der Messung nachgewiesen werden, dass die Anforderungen an dessen Homogenität eingehalten werden. Einen entscheidenden Einfluss auf die Homogenität des Prüffeldes hat der sogenannte Rührer. Bei einer MVK handelt es sich prinzipiell um einen Hohlraumresonator, in den ein mechanischer Rührer, d.h. ein elektrisch großer, drehbarer Streukörper integriert wird. Durch die Drehung des Rührers verändert sich die Feldverteilung in der MVK, was auch als Verwirbelung bezeichnet wird. Prinzipiell ergibt sich für jede Stellung des Rührers ein inhomogenes Feld mit lokalen Minima und Maxima. Ein Ziel bei der Verwendung von Modenverwirbelungskammern ist es, mit Hilfe geeigneter Verfahren Rührerstellungen zu finden, deren Feldverteilungen in Überlagerung ein möglichst homogenes Prüffeld erzeugen. Zum Lehrstuhl für Theoretische Elektrotechnik und Elektromagnetische Verträglichkeit der Technischen Universität Dresden gehört seit 2010 eine Modenverwirbelungskammer. Die Charakterisierung dieser MVK sowie eine weiterführende Untersuchung zur Wahl der Rührerstellungen bilden die Schwerpunkte der vorliegenden Arbeit. / In 2010 the Chair of Electromagnetic Theory and Compatibility of Technical University Dresden could extend its laboratories by a reverberation chamber with the dimensions 5.3 m, 3.7m and 3.0 m. Since then, a detailed characterisation of the chamber as well as further investigations have been the main emphasis of the authors research. The submitted doctoral thesis presents the obtained results. With the design, the fundamentals of operation and further characterisation of the reverberation chamber, given in Chapter 1 and 2, it aims to give an introduction and better understanding of reverberation chambers. On this basis, the authors research focused on methods for determining the independent stirrer positions in reverberations chambers. The results of the investigations are presented and summarised in chapter 3. One scope of Electromagnetic Compatibility are radiated immunity measurements. Besides the GTEM cell and the anechoic chamber the reverberation chamber gains in importance as an alternative measurement environment. A reverberation chamber is a shielded room with reflecting walls and one or more integrated mechanical stirrers. By rotating the stirrer the spatial boundary conditions for the electromagnetic field quantities are altered. The resulting change of the spatial field distribution depends on the location within the chamber and the geometry of the stirrer. Each stirrer position yields an inhomogeneous field distribution created by interfering waves. A general aim is to find a set of stirrer positions, whose superimposed field distributions create a more uniform test field. In practice, the given requirements for the homogeneity of the test field shall, with regards to an optimisation of measurement time, be realized with a minimum number of stirrer positions. In this context the term ’independent stirrer positions’ was established and describes stirrer positions, whose field distributions are linearly uncorrelated and therefore assumed to be practical for creating a more homogeneous test field using only a minimal number of stirrer positions. A general method for determining the number of independent stirrer positions in reverberation chambers is presented. The method uses a certain number of measurement positions in a defined test volume in order to characterize the spatial field distribution inside the chamber. Using the Pearson correlation coefficient the field distributions of the stirrer positions are tested for linear correlation and pairs of independent stirrer positions are determined. On this basis, cliques of pairwise independent stirrer positions are identified using appropriate algorithms. It is shown that the general method yields detailed information about the number and distribution of the independent stirrer positions and is therefore particularly suitable to evaluate other methods. Finally, the standard method according to IEC 61000-4-21 as well as selected alternative methods, that have been proposed in the past, are evaluated and compared based on the results of the general method.

En äldre industribyggnad är oftast byggd i hårda material så som tegel, stål och plåt vilket alla ger upphov till hög andel reflektioner av ljudenergi. Absorptionsnivån i dessa material är låga vilket leder till långa efterklangstider. Att montera in akustikreglerande åtgärder i dessa byggnader står i konflikt med att äldre industribyggnader ofta har ett kulturhistoriskt värde.  Syftet med arbetet var att undersöka möjligheten till att genomföra akustikreglering i en kulturhistoriskt värdefull byggnad utan att väsentligt påverka detta värde. Avseende ambitionsnivån ur akustisk synpunkt var målet att halvera efterklangstiden.  De genomförda efterklangstidsmätningarna visar på en relativ lång efterklangstid i mellanregistret och en kortare vid låga och höga frekvenser. Resultatet av de beräkningar som är genomförda visar att i den mindre, av två stycken, hyttan kan målet med en halverad efterklangstid uppnås för majoriteten av oktavbanden. Åtgärdsförslaget för den större hyttan skulle däremot inte leda till att målet uppfylls fullt ut, utan för detta skulle ytterligare åtgärder behöva sättas in. Hänsyn till hyttans kulturvärde motiverar dock att en längre efterklangstid kan accepteras. / An older industrial building is usually built in hard materials such as brick, steel and sheet metal, all of which give rise to a high proportion of reflections of sound energy. The absorption level in these materials is low, which leads to long reverberation times. Installing acoustic regulatory measures in these buildings conflicts with the fact that older industrial buildings often have a cultural-historical value.  The purpose of this work was to investigate the possibility of implementing acoustic regulations in a culturally and historically valuable building without substantially affecting its cultural value. Regarding the level of ambition from an acoustic perspective, the objective was to halve the reverberation time.  The measured reverberation time shows a relative long reverberation time in the mid frequencies and a shorter one at low and high frequencies. The results of the calculations that have been carried out show that in the smaller production hall, of two, the objective of a halved reverberation time can be achieved in the majority of the octave bands. The proposed measures for the larger production hall would not lead to the objective being fully met, but further measures would need to be implemented. Consideration of the cultural value of the glass factory justifies that a longer reverberation time can be accepted.

Measurements in a reverberation chamber use spatially averaged squared pressure to calculate sound absorption, sound power, and other sound measurements. While a reverberation chamber provides an approximation of a diffuse sound field, variations in the measurements introduce uncertainty in measurement results. Room qualification procedures require a sufficient number of source-receiver locations to obtain suitable measurements. The total acoustic energy density provides greater spatial uniformity than squared pressure, which requires fewer source-receiver positions to produce similar or better accuracy in measurement results. This paper explores the possibility of using energy density in place of squared pressure, using methods outlined in current ISO standards, by describing several experimental and analytical results.

Reverb är en effekt brukad inom bland annat musikproduktion för att mixa ljud, som flitigt används och är universellt erkänd som ett väsentligt verktyg. Däremot, inom domänen för röstinspelningar -framförallt radio och podcasts- är användningen av reverb mer begränsad, om inte obefintlig. Hur lyssnaren upplever en inspelning påverkas av efterklangen tillhörande den inspelningen. Alltså upplevs en lång efterklang tillhöra ett stort rum, medan ett mer dämpat ljud med en kort efterklang upplevs som ett litet rum. Ett nyhetsreportage som påminner om akustiken i en kyrka eller för den delen en inspelning i stil av en podcast -utan efterklang- kan upplevas svårt att lyssna på, framförallt med isolerande hörlurar. Många studier har publicerats om konceptet personligt föredragen efterklang för musik, men få finns för talad röst. Därför genomfördes denna studie med avsikt att hitta en konsensus mellan oberoende deltagare. Vilken efterklangstid föredras vid lyssning till en nyhetsrapport? Varje deltagare i studien lyssnade på sju versioner av en och samma röstinspelning i stilen av ett nyhetsreportage. Varianterna hade olika långa efterklangstider, från 0 ms till 800 ms. Därefter betygssatte deltagaren varje version av ljudklippet på en skala från 1 till 100, motsvarande hur nära inspelningen var till en perfekt lyssningsupplevelse enligt deras personliga preferens. Den extraherade datan från undersökningen indikerar en preferens mot lägre efterklangstider för det givna stimulit. Skillnaden mellan lägre efterklangstider visade sig vara mer signifikanta gentemot motsvarande intervall för längre efterklangstider. Den förväntade toppen för preferensbetygen mellan 200 och 400 ms kunde inte finnas, men avsaknaden av den kan till en del förklaras av flera faktorer, såsom: en skiljaktighet mellan ljudklippets och reverbets kvalitet, omfattningen av studien eller det faktum att ett träningsmoment saknades innan studiens start. / The reverb effect in the world of music production is frequently used and universally regarded as an essential tool. On the other hand in the domain of speech recordings -primarily radio and podcasts- is the use of reverberation more limited if even used at all. How the listener percieves a recording is affected by the reverberation of said recording. More precisely, a long reververation can be percieved as belonging to a large room, while a more damped sound with shorter reverberation sounds like a small room. A news broadcast sounding similar to church acoustics or a recording in the style of a podcast -with no room response- can be difficult to listen to, especially for a listener with isolating headphones. Many research articles and studies have been published about the concept of personally preferred reverberation for music, but very few for speech. Therefore this study was conducted with an intent to find a consensus between independent participants. What reverberation time is preferred when listening to a news report? Each participant in the study listened to a set of seven versions of a single voice recording in the style of a news report. The variants had reverberation times spanning from 0 ms up to 800. They then graded the recordings on a scale from 1 through 100 corresponding to how close to an ideal listening experience they had, according to their personal preference. The data extracted from the study points to a preference towards less reverberation time. The difference between smaller reverberation times were shown to be more significant compared to the difference between the same interval at a longer reverberation time. The expected preference-peak at between 200 and 400 ms was not found but the absence of it could be explained by several factors, such as: disparity between the quality of the soundclip and the quality of the reverb effect used, the extent of the study of the lack of a training session for the participants before the start of the study.

No description available.

<p>The aim of the research work presented here, is to contribute to the adaptation of electronic packaging towards the needs of high frequency applications. As the field of electronic packaging stretches over several very different professional areas, it takes an interdisciplinary approach to optimize the technology of electronic packaging. Besides this, an extensive knowledge of industrial engineering should be an essential part of this undertaking to improve electronic packaging. Customary advances in technology are driven by new findings and a continuous development of processes in clearly defined fields. However, in the field of the higher levels of the interconnection hierarchy, that is external to the chip level interconnections and chip packaging, it is supposed that a wide combination of disciplines and technical creativity, instead of advanced technology in a special area should produce most added value.</p><p>The thesis is divided into five areas, interlinked by the overall aim of there advantages to the common goal. These areas are the Printed Wiring Board (PWB) technology, PWB connections using flexible printed circuit boards, multiconductor cable connections, shielded enclosures and the related EMC issues, and finally the cooling of electronics. A central issue was to improve the shielded enclosures to be effective also at very high frequencies; it will be shown that shielded enclosures without apertures can cope with frequencies up to and above 15 GHz. Due to this enclosure without apertures, it was necessary to develop a novel cooling structure. This cooling structure consists of a heat sink where the PCB’s are inserted in close contact to the cooling fins on one side, whereas the other side of the heat sink is cooled by forced ventilation. The heat transfer between these parts is completely inside the same body. Tests carried out on a prototype have shown that the performance of the cooling structure is satisfactory for electronic cooling.</p><p>Another problem area that is addressed are the interconnect problems in high frequency applications. Interconnections between parts of a local electronic system, or as within the telecom and datacom field between subscribers, are commonly accomplished by cable connections. In this research work multiconductor cables are examined and a patented novel cable-connector for high frequency use is presented. Further, an experimental complex soldering method between flexible printed circuits boards and rigid printed circuits boards, as part of connections between PCBs, is shown. Finally, different sectors of the PCB technology for high frequency applications are scrutinized and measurements on microstrip structures are presented.</p>