3 research outputs found
Non-destructive dielectric measurements and calibration for thin materials using waveguide-coaxial adaptors
This paper focuses on the calibration of apertures for rectangular waveguides using open-short-load (OSL) standards and transmission-line (TL) approaches. The reflection coefficients that were measured using both calibration techniques were compared with the coefficients acquired using the thru-reflect-line (TRL) method. In this study, analogous relationships between the results of OSL calibration and TL calibration were identified. In the OSL calibration method, the theoretical, open-standard values are calculated from quasi-static integral models. The proposed TL calibration procedure is a simple, rapid, broadband approach, and its results were validated by using the OSL calibration method and by comparing the results with the calculated integral admittance. The quasi-static integral models were used to convert the measured reflection coefficients to relative permittivities for the infinite samples and the thin, finite sample
Analytical and numerical analysis of fringing field at aperture open-ended waveguides
This paper presents an improved formulation of the admittance model for open-ended waveguides by including its fringing field effects. The results were compared to both measured and calculated values using finite element method for free space
Ătude des sources plasma micro-onde Ă structure coaxiale pour la conception amont d'applicateurs Ă transformateur d'impĂ©dance intĂ©grĂ©. Influence de la pression, de la gĂ©omĂ©trie et de la frĂ©quence d'excitation
The work done within the framework of this thesis focuses on the study of magnetized and nonmagnetizedplasmas produced by coaxial structures that serve both as wave propagator and as plasma matchedimpedance coupler but also as investigation and characterization probe of the discharge. Special attention isgiven to the efficiency of coupling between the electromagnetic wave and the discharge and of speciesproduction, for different operating conditions: excitation frequency (352 and 2450 MHz), magnetic configurationand geometry of the applicator. Quantitative and comparative analysis presented in this work is based both on anexperimental and a theoretical approach. Developed analytical models and conducted electromagnetic simulationare set in connection with the experimental measurements in order to determine, on the one hand, the plasmaimpedance de-embedded of the wave propagation structure and, on the other hand, the global and localabsorption of the wave. From the experimental point of view, appropriate techniques and methods have thereforebeen developed and implemented such as, for example, the impedance plane shift method, or autointerferometry.The parametric study, conducted on a pressure range extended over several decades (10-4 - 10Torr) and power ratings from one to several hundred watts, led to a thorough investigation of the coupling type(capacitive, inductive, resistive ) which is highly dependent on the discharge characteristics and thus of theoperating parameters. Their correlation, combined with the analysis of propagation modes in a magnetizedplasma, has helped locate more accurately the areas of coupling and to identify the main power absorptionmechanisms involved. The main results obtained for the two frequencies confirm a better production efficiencyof charged species at a higher frequency (2450 MHz), the presence of a more substantial hot electron populationand a spatial expansion of the plasma when the frequency is low (352 MHz). As the solid state 352 MHztechnology is more advantageous compared to that at 2450 MHz from the viewpoint of the cost of thecomponents, it could be interesting for processes aiming to produce active chemical species. However itsinefficient coupling, of capacitive type induced by frequency reduction, requires an increased attention at thelevel of coupler configuration. For upstream development of couplers, the analytical models and theexperimental results obtained in this thesis should be a key tool in the design of high-performance microwaveplasma sources.Le travail effectuĂ© dans le cadre de cette thĂšse porte sur lâĂ©tude des plasmas magnĂ©tisĂ©s et nonmagnĂ©tisĂ©s produits par des structures coaxiales qui font office Ă la fois de propagateur dâonde et de coupleur Ă impĂ©dance adaptĂ©e au plasma, mais aussi de sonde dâinvestigation et de caractĂ©risation de la dĂ©charge. Une attention particuliĂšre est accordĂ©e Ă lâefficacitĂ© de couplage entre lâonde Ă©lectromagnĂ©tique et la dĂ©charge et de production dâespĂšces, et ce pour diffĂ©rentes conditions opĂ©ratoires : frĂ©quence dâexcitation (352 et 2450 MHz),configuration magnĂ©tique, gĂ©omĂ©trie de lâapplicateur. Lâanalyse quantitative et comparative prĂ©sentĂ©e dans ce travail sâappuie aussi bien sur une approche expĂ©rimentale que thĂ©orique. Les modĂšles analytiques dĂ©veloppĂ©s etla simulation Ă©lectromagnĂ©tique rĂ©alisĂ©e permettent dâextraire Ă partir des mesures expĂ©rimentales, dâune partl âimpĂ©dance du plasma dĂ©corrĂ©lĂ©e de celle de la structure de propagation de lâonde, et dâautre part, lâabsorption globale et locale de lâonde. Du point de vue expĂ©rimental, des techniques et mĂ©thodes appropriĂ©es ont donc Ă©tĂ© dĂ©veloppĂ©es et mises en oeuvre comme, par exemple la mĂ©thode de changement de plan dâimpĂ©dance, ou encore lâauto-interfĂ©romĂ©trie. LâĂ©tude paramĂ©trique, menĂ©e sur un domaine de pression Ă©tendu sur plusieurs dĂ©cades(10-4 â 10 Torr) et pour une gamme de puissances allant de un Ă plusieurs centaines de watts, a permis une investigation minutieuse du type de couplage (capacitif, inductif, rĂ©sistif) qui est fortement dĂ©pendant des caractĂ©ristiques de la dĂ©charge et donc des paramĂštres opĂ©ratoires. Leur mise en corrĂ©lation, associĂ©e Ă lâanalyse des modes de propagation dans un plasma magnĂ©tisĂ©, a permis de localiser avec plus de prĂ©cision les zones de couplage et dâidentifier les principaux mĂ©canismes dâabsorption de lâonde mis en jeu. Les principaux rĂ©sultats obtenus confirment une meilleure efficacitĂ© de production dâespĂšces chargĂ©es Ă une frĂ©quence plus Ă©levĂ©e (2450MHz), et la prĂ©sence dâune population dâĂ©lectrons chauds plus consĂ©quente ainsi quâune extension spatiale du plasma lorsque la frĂ©quence est plus faible (352 MHz). Comme la technologie 352 MHz Ă Ă©tat solide est plus avantageuse du point de vue du coĂ»t des composants, comparĂ©e Ă 2450 MHz, elle pourrait sâavĂ©rer intĂ©ressante pour des procĂ©dĂ©s visant la production dâespĂšces chimiquement actives. Toutefois, le couplage, peu efficace, de type capacitif induit par la diminution de la frĂ©quence, requiert une attention accrue au niveau de la configuration du coupleur. Pour le dĂ©veloppement en amont des coupleurs, les rĂ©sultats issus de ce travail de thĂšse et les modĂšles analytiques dĂ©veloppĂ©s devraient constituer un outil dĂ©terminant dans la conception de sources plasma micro-onde performantes