This work presents the development of an in-plane vertical micro-coaxial probe using bulk micromachining technique for high frequency material characterization. The coaxial probe was fabricated in a silicon substrate by standard photolithography and a deep reactive ion etching (DRIE) technique. The through-hole structure in the form of a coaxial probe was etched and metalized with a diluted silver paste. A co-planar waveguide configuration was integrated with the design to characterize the probe. The electrical and RF characteristics of the coaxial probe were determined by simulating the probe design in Ansoft’s High Frequency Structure Simulator (HFSS). The reflection coefficient and transducer gain performance of the probe was measured up to 65 GHz using a vector network analyzer (VNA). The probe demonstrated excellent results over a wide frequency band, indicating its ability to integrate with millimeter wave packaging systems as well as characterize unknown materials at high frequencies. The probe was then placed in contact with 3 materials where their unknown permittivities were determined. To accomplish this, the coaxial probe was placed in contact with the material under test and electromagnetic waves were directed to the surface using the VNA, where its reflection coefficient was then determined over a wide frequency band from dc-to -65GHz. Next, the permittivity of each material was deduced from its measured reflection coefficients using a cross ratio invariance coding technique. The permittivity results obtained when measuring the reflection coefficient data were compared to simulated permittivity results and agreed well. These results validate the use of the micro-coaxial probe to characterize the permittivity of unknown materials at high frequencies up to 65GHz.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Flanged coaxial probes are widely used to conduct accurate, broadband permittivity measurements of various dielectric materials. A metrology study, discussed in [1], revealed that small perturbations in measured permittivity data, are due to escaping common-mode (CM) current that propagates onto exposed VNA feed cabling. This is not considered in published permittivity extraction algorithms, like the National Institute of Standards and Technology (NIST) full-wave code that assumes an infinite flange radius. To characterise this effect we validate a finite volume time domain (FVTD) CST simulation model of an SMA coaxial probe, by probing sensitive E-fields in a metallic shielding cylinder, placed around it. For this process, electro-optic (EO) E-field sensors are considered and a Mach-Zehnder type sensor is designed. Manufacturing difficulties discontinues this approach, but the revisited extended centre conductor E-field probing technique proves successful. The technique entails a high dynamic range, two-port VNA measurement. Through CST we gain knowledge of the physics behind the CM-problem and the behaviour of fields around the coaxial probe. Different shielding environments are simulated to establish their ability to impede CM-current coupling onto measurement cabling. To study the CM-effect on extracted permittivity results, the investigation is extended to Short-Open-Load (SOL) calibrated face-plane measurements of dielectric solids. A CST model, which considers escaping CM-energy, is used to generate open circuit (OC) calibration coefficients and to serve as an independent extraction method. We inspect the effect of different shielding environments and through CST, extract accurate permittivity results for e00, to a degree not previously achieved for such systems. This allows comment on the infinite-flange-radius assumption of the NIST method and proves the significance of the CM-effect. / AFRIKAANSE OPSOMMING: Geflensde koaksiale probes word algemeen in die praktyk gebruik om akkurate, wyeband permitiwiteitmetings van diëlektriese materiale te verrig. ’n Studie wat in [1] bespreek word, dui aan dat klein verskynsels in gemete resultate, verband hou met gemene-modus (GM) stroom, wat ontsnap en teenwoording is aan die buitekant van onbeskermde voerkabels. Hierdie verkynsel word nie deur huidige volgolf ekstraksie-algoaritmes, soos die van NIST wat ’n onëindige flensradius aanvaar, in ag geneem nie. Om die GM-effek te karakteriseer, verifieer ons ’n eindige-volume tyd-gebied CST simulasiemodel, deur sensitiewe metings binne ’n silidriese metaalskerm, wat om so ’n probe geplaas word. Vir hierdie meting word elektro-optiese E-veld probes eers oorweeg. In gevolg word ’n Mach-Zehnder-tipe probe ontwerp, maar vervaardigingsprobleme en tyd-oorwegings kniehalter hierdie benadering. Heroorweging van die verlengde koaksiale sentraalgeleier, E-veld-probe tegniek, wat hoë dinamiese bereik twee-poort netwerkanaliseerder metings behels, slaag uiteindelik in hierdie doel. CST maak dit nou moontlik om die GM stroomprobleem te simuleer en spesefieke veldgedrag te kan waarneem. Verskillende afskermingsmetodes se vermoë om GM-koppeling na kabels te beperk word ondersoek. Die GM studie word uitgebrei na SOL-gekalibreerde, flensvlakverwysde permitwiteitmetings van diëlektriese vastestowwe. ’n CST model, wat GM stroom in ag neem, word gebruik om oopgeslote kalibrasiekofisiënte te genereer en dien ook as ‘n alternatiewe permitiwiteit ekstraksiemetode. Die effek van die verskillende afskermingstegnieke word ondersoek en deur die CST metode te gebruik, word ’n aansienlike verbetering in akkuraatheid van e00 waardes verkry. Dit regverdig kommentaar oor die aannames wat in die NIST metode gemaak word en beklemtoon die belangrikheid om GM stroom in ag te neem.

With global warming on the rise and the urge for conserving our natural resources, it becomes very important that proper steps are taken to protect our natural resources and utilize them efficiently. Forest fires are one of the many issues on the charts towards protection of natural resources. The catastrophic aftermaths caused by forest fires are known to all. The causes for these fires could be known/unknown natural causes or human intervention. Remote sensing techniques use the electromagnetic radiation in the RF/Microwave region, emitted from an object. The amount of energy emitted from an object depends on its present conditions, primarily its temperature and its emissivity. The sensing devices used in such measurements are classified into active and passive sensors. Herein, passive radiometry is used to investigate a model for the propagation of subsurface radiation from underground forest fires through upper ground layers of soil till the land-air interface. Passive radiometry involves capturing the radiation incident on a radiometer antenna aperture directly or deflected from several objects. The energy emitted from sources above 0K is collected and is compared with the calibration standards to estimate the physical quantity under test. Detecting forest fires is one of the potential applications of passive radiometry investigated here.

This thesis describes possibilities of measuring permittivity of various materials, especially with coaxial probe method. It describes character of measuring method, hardware requirements and how to calculate values from the measured. Objective of this thesis is to design measuring station for measuring permittivity of materials with coaxial probe including calibration set. Code in Matlab is also programmed and whole station is tested with known samples to discuss measurement accuracy.

Las emulsiones del tipo agua en aceite (w/o) y aceite en agua (o/w) están compuestas por una mezcla de aceite, agua, lodo y otros agentes. Se pueden encontrar en el proceso y/o en los vertidos de diferentes tipos de industrias, tales como refinerías de petróleo, plantas procesadoras de aceite de consumo, industrias farmacéuticas, industrias de alimentos, etc. El calentamiento de un material a una frecuencia de microondas depende de la frecuencia de la onda electromagnética y de las propiedades dieléctricas, así como de la acumulación de energía interna que va ligada a la profundidad de penetración del campo dentro del material. De este modo, el conocimiento preciso de las propiedades dieléctricas de los materiales es fundamental para conocer su comportamiento bajo la influencia de un campo electromagnético. El objetivo general de esta tesis es proponer métodos alternativos basados en la tecnología de microondas para monitorizar, caracterizar y/o separar emulsiones. Para ello, se determinaron los protocolos de preparación de emulsiones prototipo en el laboratorio, empleando dos fases distintas (ácido oleico y aceite mineral SAE 40), de composición similar a las encontradas en la industria. Paralelamente se ha seleccionado, montando y calibrando un sistema de medida de propiedades dieléctricas en un rango de frecuencias de 1 a 4 GHz (rango cercano a la frecuencia estándar de calentamiento f =2.45 GHz) y de esta manera se ha obtenido un amplio espectro de información del comportamiento dieléctrico de las emulsiones, que servirán para diseñar en una fase posterior aplicadores de microondas. En base a este estudio preliminar se planteó una experiencia piloto con emulsiones reales presentes en el proceso de extracción de aceite de palma africana, con el fin de determinar el efecto de las microondas en la separación y en la calidad del aceite recuperado. / Pérez Páez, R. (2009). Aplicación de microondas en el tratamiento de emulsiones del tipo agua en aceite (w/o) y aceite en agua (o/w) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/4328

Abstract The purpose of this task is to synthesize a dielectric substrate material through a sintering process, which can be used for non-invasive physiological sensor development. Low loss, high dielectric constant ceramic material is used. Sintering process is employed to ensure stable structure and homogeneous dielectric properties of the substrate. Samples were prepared with TiO2 and in combination with CuO and Al2O3. All samples were measured and validated in 500 MHz to 20 GHz frequency range. Characterization measurements were performed with a Vector Network Analyzer, FieldFox N9918A, and connected to Keysight, open ended coaxial probe and performance probe. Reflection based measurement method was used due to its simplicity, speed and requirement of wideband data. The dielectric measurement results of developed samples show non-frequency dispersive behaviour, high dielectric constant and data was also selected at 2.45 GHz in aligned to the industrial, scientific and medical band. The resulting measurements show the highest dielectric constant of 16.6 at 2.45 GHz with a very low loss behaviour. / Målet är att syntetisera ett material, genom sintringsprocess, som kan användas som ett dielektriskt substrat för utveckling av sensorer. Det dielektriska materialet har keramisk materialstruktur och innehar högt dielektricitetskonstant med låga dielektriska materialförluster. Denna uppgift kräver att dielektriska materialet ska vara stabilt och inneha isotropiska egenskaper efter att genomgått sintringsprocess. Proverna förberedes med TiO2 och även i kombination med TiO2 tillsammans med CuO och Al2O3. Proverna mäts i frekvensområdet 500 MHz till 20 GHz. Mätningarna utförs med Vector Network Analyzer, FieldFox N9918A från Keysight. Resultat som visas och jämförs i arbetet är tagna vid 2.45 GHz eftersom det används och är standardiserat för medicinskt frekvensband. Högsta uppmätta dielektricitetskonstant har värdet av 16,6. Resultaten visar även låga förluster i dielektrikumet.

[ES] La constante evolución de la tecnología y la búsqueda de nuevas aplicaciones que mejoren la vida de las personas ha llevado a la incorporación de estas tecnologías en el organismo. Las redes inalámbricas de área corporal (WBAN) son un buen ejemplo de esto, que consisten en redes de comunicaciones ubicadas en el propio cuerpo, tanto en la superficie como implantadas en su interior mediante el uso de dispositivos inalámbricos. Estas redes utilizan el cuerpo humano como medio de transmisión, por lo que debe evaluarse la influencia del mismo sobre la propagación. Además, las nuevas generaciones de comunicaciones móviles se están moviendo hacia el uso de frecuencias cada vez más altas, como las ondas milimétricas, que son más sensibles a la presencia de cualquier objeto en el entorno, incluidos los humanos. La investigación y el diseño de antenas y dispositivos que tengan en cuenta el cuerpo humano requiere pruebas en el entorno donde se supone que deben usarse. Los fantomas se convierten en una herramienta para evaluar la transmisión de señales electromagnéticas en un medio equivalente al cuerpo para evitar la experimentación en humanos o animales. Además de eso, se puede estudiar la influencia de estas ondas electromagnéticas sobre los propios tejidos en cuanto a la tasa de absorción específica (SAR). / [CA] L'evolució constant de la tecnologia i la recerca de noves aplicacions que milloren la vida de les persones ha portat a la incorporació d'aquestes tecnologies en l'organisme. Les xarxes sense fils d'àrea corporal (WBAN) són un bon exemple d'açò, que consisteixen en xarxes de comunicacions ubicades al propi cos, tant en la superfície com implantades en el seu interior mitjançant l'ús de dispositius sense fils. Aquestes xarxes empren el cos humà com a medi de transmissió, per la qual cosa se n'ha d'avaluar la influència sobre la propagació. A més, les noves generacions de comunicacions mòbils s'estan movent cap a l'ús de freqüències cada vegada més altes, com les ones mil·limètriques, que són més sensibles a la presència de qualsevol objecte en l'entorn, incloent-hi els humans. La investigació i el disseny d'antenes i dispositius que tinguen en compte el cos humà requereix proves en l'entorn on se suposa que han d'usar-se. Els fantomes esdevenen una eina per a avaluar la transmissió de senyals electromagnètics en un medi equivalent al cos per tal d'evitar l'experimentació en humans o animals. A més d'això, es pot estudiar la influència d'aquestes ones electromagnètiques sobre els teixits mateixos en relació amb la taxa d'absorció específica (SAR). / [EN] The constant evolution of technology and the search for new applications that improve people's lives has led to the arrival of the incorporation of these technologies in the organism. Wireless body area networks (WBANs) are a good example of this, consisting of communications networks located in the body itself, both on the surface and implanted inside it through the use of wireless devices. These networks use the human body as the transmitting medium, so its influence over the propagation has to be assessed. Besides, new generations of mobile communications are moving towards the use of higher frequencies, as the millimetre waves, which are more sensitive to the presence of any object in the environment, including humans. The research and design of antennas and devices that take into account the human body requires testing in the environment where these are supposed to be used. Phantoms become a tool for evaluating the transmission of electromagnetic signals in a body-equivalent medium in order to avoid experimentation on humans or animals. In addition to that, the influence of these electromagnetic waves over the tissues themselves can be studied with regard to the specific absorption rate (SAR). / This thesis has been possible thanks to the funding contribution of the Universitat Polit`ecnica de Val`encia through the PAID-01-16 programme. This work was also supported by the UPV-IIS La Fe programme (STUDER, 2016 and EMOTE, 2017). The research stay was supported by the European Union’s Erasmus+ funding programme under a traineeship grant. / Castelló Palacios, S. (2019). Wideband Electromagnetic Body Phantoms for the Evaluation of Wireless Communications in the Microwave Spectrum [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/132182