Design and analysis of an open-ended waveguide probe for material characterization

Nondestructive evaluation of stratified (layered) composite structures at microwave and millimeter wave frequencies is of great interest in many applications where simultaneous determination of the complex dielectric properties and thicknesses of multiple layers is desired. Open-ended rectangular waveguide probes are effective tools for this purpose. The technique requires a full-wave electromagnetic model that accurately calculates the complex reflection coefficient as a function of frequency and material properties. Subsequently, this information is used in conjunction with the measured complex reflection coefficient to evaluate the sought for material properties. This thesis presents simulated and measured data to investigate the influence that measurement system noise, which contaminates the measured complex reflection coefficient, has on estimating material properties. It will be shown however, that the foremost contributor to errors in estimating material properties is not due to system noise, but rather, is due to an inconsistency between the electromagnetic model and the measurement setup. More specifically, the electromagnetic model assumes an infinite waveguide flange while measurements are conducted using a finite-size flange. Consequently, the results of the model and those from measurements may not be sufficiently alike for accurate dielectric property and thickness evaluation. The work presented here investigates the effect of using an open-ended waveguide with a standard finite-sized flange on the error in evaluating the complex dielectric properties of a composite structure. Additionally, the design of a novel flange that markedly reduces this undesired effect by producing very similar electric field properties, at the flange aperture, to those created by an infinite flange will be presented and verified in measurement --Abstract, page iii

Dielectric, magnetic and electromagnetic shielding properties of Poly-(3,4ethylenedioxythiophene)-maghnite associated with different fillers with any non-canonical shape

A new inverse measuring technique that corrects non-desired sample displacements and can handle any kind of sample shapes is presented. It is applied to the estimation of permittivity and permeability of Poly-(3,4ethylenedioxythiophene)-maghnite (PEDOT-Mag) associated with different additives such as iron, copper, and hydrogen. This electromagnetic characterization has been performed over the 9 to 11 GHz frequency range by comparing the simulated and measured scattering parameters of a partially filled WR-90 waveguide. Additionally, the reflection, absorption multiple reflection losses and the shielding effectiveness of these materials have been calculated. Results show higher values of dielectric constant and loss factor for PEDOT-Mag-copper, than those compounds associated with hydrogen or iron. As expected, the highest permeability values are achieved by PEDOT-Mag-iron. The composite PEDOT-Mag-copper exhibits higher attenuation constant, absorption loss, multiple reflection loss and shielding efficiency values than composites associated with iron or hydrogen. PEDOT-Mag-hydrogen, however, shows the highest reflection loss values

Microwave characterization of low-loss FDM 3-D printed ABS with dielectric-filled metal-pipe rectangular waveguide spectroscopy

Over time the accuracy and speed by which a material can be characterized should improve. Today, the Nicolson-Ross-Weir (NRW) methodology represents a well-established method for extracting complex dielectric properties at microwave frequencies, with the use of a modern vector network analyzer. However, as will be seen, this approach suffers from three fundamental limitations to accuracy. Challenging NRW methods requires a methodical and robust investigation. To this end, using a dielectric-filled metal-pipe rectangular waveguide, five independent approaches are employed to accurately characterize the sample at the Fabry-Pérot resonance frequency (non-frequency dispersive modeling). In addition, manual Graphical and automated Renormalization spectroscopic approaches are introduced for the first time in waveguide. The results from these various modeling strategies are then compared and contrasted to NRW approaches. As a timely exemplar, 3-D printed acrylonitrile-butadiene-styrene (ABS) samples are characterized and the results compared with existing data available in the open literature. It is found that the various Fabry-Pérot resonance model results all agree with one another and validate the two new spectroscopic approaches; in so doing, exposing three limitations of the NRW methods. It is also shown that extracted dielectric properties for ABS differ from previously reported results and reasons for this are discussed. From measurement noise resilience analysis, a methodology is presented for determining the upper-bound signal-to-noise ratio for the vector network analyzer (not normally associated with such instrumentation). Finally, fused deposition modeling (FDM) 3-D printing results in a non-homogeneous sample that excites open-box mode resonances. This phenomenon is investigated for the first time, analytically and with various modeling strategies

Design and performance evaluation of millimeter-wave flat lens antennas for communications, radar and imaging applications

Millimeter-wave systems introduce a set of particular severe requirements from the antenna point of view in order to achieve specific performances. In this sense, high directive antennas are required to overcome the huge extra path loss. Moreover, each particular application introduces additional requirements. For example, in very high throughput (VHT) wireless personal area networks (WPANs) communication systems at 60 GHz band beam-steering antennas are needed to deal with high user random mobility and human-body shadowing characteristic of indoor environments. Similarly, beam-steering capabilities are also needed in automotive radar applications at 79 GHz, since the determination of the exact position of an object is essential for most of the functions realized by the radar sensor. In the same way, beam-scanning, which is still commonly mechanically performed nowadays, is also needed in passive imaging systems at 94 GHz. Finally, from the integration perspective, the antennas must be small, low-profile, light weight and low-cost, in order to be successfully integrated in a commercial millimeter-wave wireless system. For these reasons, many types of antenna structures have been considered to achieve high directivity and beam-steering capabilities for the aforementioned millimeter-wave communication, radar and imaging applications at 60, 79 and 94 GHz. The most part of the currently adopted solutions are based on the expensive, complex and bulky phased-array antena concept. Actually, phased-array antenna systems can scan the beam at a fast rate. However, they require a complex integration of many expensive, lossy and bulky circuits, such as solid-state phase shifters and beam-forming networks. This doctoral thesis has contributed to the study, development, and assessment of the performance of innovative antena solutions in order to improve the existing architectures at millimeter-wave frequencies, conveniently solving the problems related specifically to short-range high data rate communication systems at 60 GHz WPAN band (including future 5G millimeter-wave systems), automotive radar sensors at 79 GHz band, and communications, radar, and imaging systems at 94 GHz. The specific goals pursued in this work, focused on defining an alternative antenna architecture able to achieve a full reconfigurable 2-D beam-scanning of high gain radiation beams at millimeter-wave frequencies, has been fulfilled. In this sense, this thesis has been mainly devoted to study in depth and practically develop the fundamental part of an innovative switched-beam antenna array concept: novel inhomogeneous gradient-index dielectric flat lenses, which, despite their planar antenna profile configurations, allow full 2-D beam-scanning of high gain radiation beams. A transversal study, going from theoretical investigations, passing by numerical analysis, new fabrication strategies, performance evaluation, and to full experimental assessment of the new antenna architectures in real application environment has been successfully carried out.Los sistemas a frecuencias de ondas milimétricas introducen una serie de requisitos muy estrictos desde el punto de vista de la antena con el objetivo de conseguir unos rendimientos específicos. En este sentido, se requieren antenas con una muy alta directividad con tal de conseguir superar las enormes pérdidas adicionales por propagación. Además, cada aplicación en concreto introduce unos requisitos adicionales. Por ejemplo, en redes de área personal de alta velocidad para sistemas de comunicación a la banda de 60 GHz, antenas con la capacidad de reconfiguración del haz de radiación son necesarias para poder tratar la problemática de la alta movilidad de los usuarios en entornos cerrados. De la misma forma, capacidades de reconfiguración de la orientación del haz de radiación son necesarias en aplicaciones relacionadas con radar de automoción a 79 GHz, dado que la determinación de la posición exacta de un objeto es esencial para muchas de las funciones del sensor de radar. De forma muy similar, la capacidad de apuntamiento del haz, que muchas veces todavía se realiza mediante sistemas mecánicos, es también imprescindible en sistemas de escaneo para aplicaciones biomédicas y de seguridad a 94 GHz. Finalmente, desde la perspectiva de la integración, las antenas deben ser eléctricamente pequeñas, ligeras, y económicas para poder ser incorporadas a un sistema inalámbrico comercial a frecuencias de onda milimétricas. Por todos estos motivos, diferentes tipos de estructuras de antenas han sido propuestos para conseguir alta directividad, junto con capacidades de reconfiguración y apuntamiento del haz de radiación para las aplicaciones anteriormente mencionadas y descritas en la banda de 60, 79, y 94 GHz. La solución tradicionalmente adoptada en este tipo de casos està estrictamente basada en el siempre caro, complejo y aparatoso concepto del phased-array. De hecho, los phased-arrays permiten el rápido escaneo de haces de radiación de alta directividad. Sin embargo, el hecho que requieran una compleja integración de muchos y caros componentes a alta frecuencia, tales como desfasadores de estado sólido o redes de conformación, los cuales introducen ciertos niveles de pérdidas, siendo además aparatosos, hacen que esta solución resulte inviable. La presente tesis doctoral contribuye al estudio, desarrollo, y ensayo experimental del rendimiento de soluciones de antenas innovadoras para la mejora de las existentes arquitecturas de antena en la banda frecuencial de las ondas milimétricas, convenientemente solucionando los problemas asociados específicamente a los sistemas de comunicación de corto alcance y alta velocidad a 60 GHz (incluyendo los futuros sistemas 5G a milimétricas), a los sistemas de radar de automoción a 79 GHz, y a los sistemas de comunicación, radar, y escaneo para aplicaciones a 94 GHz. Los objetivos específicos perseguidos en este trabajo académico, focalizados en definir una arquitectura alternativa de antena, capaz de conseguir una completa reconfiguración y escaneo de los haces de radiación en dos dimensiones del espacio a frecuencias de onda milimétricas, se han conseguido plenamente. En este sentido, esta tesis doctoral ha sido dedicada esencialmente al estudio en profundidad y desarrollo práctico de la parte fundamental del innovador concepto del switchedbeam array: nuevas lentes dieléctricas inhomogéneas de gradiente de índice con estructura plana, las cuales, a pesar de su configuración física totalmente llana, permiten una reconfiguración total, en dos dimensiones del espacio, de haces de radiación de alta directividad. Un estudio eminentemente transversal, que abarca desde la investigación teórica, pasando por el análisis numérico, nuevas metodologías y técnicas de fabricación, evaluación de rendimientos, hasta una completa caracterización y ensayo del rendimiento en entornos reales de aplicación de las nuevas arquitecturas de antena, se ha llevado a cabo con total éxito.Els sistemes a freqüències d'ones mil·limètriques introdueixen una sèrie de requisits molt estrictes des del punt de vista de l'antena per tal d’aconseguir uns rendiments específics. En aquest sentit, es requereixen antenes amb una alta directivitat per aconseguir superar les enormes pèrdues addicionals per propagació. A més a més, cada aplicació en concret introdueix uns requeriments addicionals . Per exemple, en xarxes d'àrea personal d'alta velocitat per a sistemes de comunicació a la banda de 60 GHz, antenes amb la capacitat de reconfiguració del feix de radiació són necessàries per tal de poder tractar la problemàtica de l'alta mobilitat dels usuaris en entorns tancats . De la mateixa manera, capacitats de reconfiguració de l'orientació del feix de radiació són necessàries en aplicacions associades a radar d'automoció a 79 GHz, donat que la determinació de la posició exacta d'un objecte és essencial per moltes de les funcions portades a terme pels ens or del radar. De forma molt similar, la capacitat d'apuntament del feix, que moltes vegades encara es realitza per mitjà de sistemes mecànics, és també imprescindible en sistemes d'escaneig per aplicacions mèdiques i de seguretat a 94 GHz. Finalment, des de la perspectiva de la integració, les antenes han de ser petites en termes elèctrics, lleugeres, i econòmiques per tal de poder ser incorporades en un sistema sense fils comercial a freqüència d'ones mil·limètriques. Per aquestes raons , diversos tipus d'estructures d'antenes han sigut proposats per aconseguir alta directivitat, conjuntament amb la capacitat d'apuntament del feix de radiació per les aplicacions anteriorment descrites a les bandes de 60, 79, i 94 GHz. La solució tradicionalment adoptada en aquests casos és estrictament basada en el sempre car, complexe, i aparatós concepte del phased-array. De fet, els phased-arrays tenen la capacitat de reconfigurar a gran velocitat feixos de radiació d'alta directivitat. Tot i això, el fet que requereixin la complexa integració de molts components cars a alta freqüència, amb certs nivells de pèrdues i aparatosos, com són els desfasadors d'estat sòlid, i les xarxes de conformació, fan d'aquesta solució inviable. La present tesis doctoral contribueix a l'estudi, des envolupament, i assaig experimental del rendiment de solucions d'antenes innovadores per tal de millorar les existents arquitectures d'antena a la banda freqüencial de les ones mil·limètriques, convenientment solucionant els problemes associats específicament als sistemes de comunicació de rang proper d'alta velocitat a 60 GHz (incloent els futurs sistemes 5G a mil·limètriques ), als sistemes de radar d'automoció a la banda dels 79 GHz, i als sistemes de comunicació, radar, i escaneig per aplicacions a 94 GHz. Els objectius específics perseguits en aquest treball acadèmic, focalitzats en definir una arquitectura d'antena alternativa, capaç d'aconseguir una completa reconfiguració i escaneig dels feixos de radiació en dues dimensions de l'espaia freqüències d'ona mil·limètriques , s'han plenament aconseguit. En aquest sentit, aquesta tesis doctoral s'ha dedicat essencialment a l'estudi en profunditat i desenvolupament pràctic de la part fonamental de l'innovador concepte del switched-beam array: noves lents dielèctriques inhomogenees de gradient d'índex amb estructura planar, les quals, tot i preservar una configuració física totalment plana, permeten una reconfiguració total en dues dimensions de l'espai de feixos de radiació d'alta directivitat. Un estudi transversal, que comprèn des de la investigació teòrica, passant per l'anàlisi numèric, noves metodologies i tècniques de fabricació, avaluació de rendiments, fins a una completa caracterització i assaig del rendiment en entorns reals d'aplicació de les noves arquitectures d'antena s'ha dut a terme amb total èxit

Enabling Solutions for Integration and Interconnectivity in Millimeter-wave and Terahertz Systems

Recently, Terahertz (THz) systems have witnessed increasing attention due to the continuous need for high data rate transmission which is mainly driven by next-generation telecommunication and imaging systems. In that regard, the THz range emerged as a potential domain suitable for realizing such systems by providing a wide bandwidth capable of achieving and meeting the market requirements. However, the realization of such systems faces many challenges, one of which is interconnectivity and high level of integration. Conventional packaging techniques would not be suitable from performance perspective above 100 GHz and new approaches need to be developed. This thesis proposes and demonstrates several approaches to implement interconnects that operate above 100 GHz. One of the most attractive techniques discussed in this work is to implement on-chip coupling structures and insert the monolithic microwave integrated circuit (MMIC) directly into a waveguide (WG). Such approach provides high level of integration and eliminates the need of galvanic contacts; however, it suffers from a major drawback which isthe propagation of parasitic modes in the circuit cavity if the MMIC is large enough to allow such modes to propagate. To mitigate this problem, this work suggests and investigates the use of electromagnetic bandgap (EBG) structures that suppresses those modes such as bed of nails and mushroom-type EBG structures. The proposed techniques are used to implement several on-chip packaging solutions that have an insertion loss as low as 0.6 dB at D-band (110-170 GHz). Moreover, the solutions are demonstrated in several active systems using various commercial MMIC technologies. The thesis also investigates the possibility of utilizing the commercially available packaging technologies such as Embedded Wafer Level Ball Grid Array (eWLB) packaging. Such technology has been widely used for integrated circuits operating below 100 GHz but was not attempted in the THz range before. This work attempts to push the limits of the technology and proposes novel solutions based on coupling structures implemented in the technology’s redistribution layers. The proposed solutions achieve reasonable performance at D-band that are suitable for low-cost mass production while allowing heterogeneous integration with other technologies as well. This work addresses integration challenges facing systems operating in the THz range and proposes high-performance interconnectivity solutions demonstrated in a wide range of commercial technologies and hence enables such systems to reach their full potential and meet the increasing market demands

Nano-Fluidic Millimeter-Wave Lab-on-a-Waveguide Sensor for Liquid-Mixture Characterization

This paper reports on a miniaturized lab-on-a-waveguide liquid-mixture sensor, achieving highly-accurate nanoliter liquid sample characterization, for biomedical applications. The nanofluidic-integrated millimeter-wave sensor design is based on near-field transmission-line technique implemented by a single loop slot antenna operating at 91 GHz, fabricated into the lid of a photolaser-based subtractive manufactured WR-10 rectangular waveguide. The nanofluidic subsystem, which is mounted on top of the antenna aperture, is fabricated by using multiple Polytetrafluoroethylene (PTFE) layers to encapsulate and isolate the liquid sample during the experiment, hence, offering various preferable features e.g. noninvasive and contactless measurements. Moreover, the sensor is reusable by replacing only the nanofluidic subsystem, resulting a cost-effective sensor. The novel sensor can measure a liquid volume of as low as 210 nanoliters, while still achieving a discrimination accuracy of better than 2% of ethanol in the ethanol/deionized-water liquid mixture with a standard deviation of lower than 0.008 from at least three repeated measurements, resulting in the highest accurate ethanol and DI-water discriminator reported to date. The nanofluidic-integrated millimeter-wave sensor also offers other advantages such as ease of design, low fabrication and material cost, and no life-cycle limitation of the millimeter-wave subsystem

Microfluidic capillary in a waveguide resonator for chemical and biochemical sensing

This thesis presents a novel microwave sensor for the characterisation of fluids with the integration of a microfluidic capillary. Various designs and fabrication methods were investigated for the integrated microfluidic capillary. SU-8 and PDMS were investigated as possible materials, however proved difficult to produce large volumes of capillaries. PMMA a cheap readily available material was also investigated. Using an Epilog CO2 laser ablation machine rapid prototyping of microfluidic capillaries was achieved using PMMA. Two microwave resonator designs are proposed as non-contact sensing devices. The first design utilizes an E-plane filter in a split-block rectangular waveguide housing. This offers advantages in enhanced near fields and simple manufacturing techniques. Simulation and experimental results are presented, demonstrating sensitivity of such microwave sensors. Various materials under test were used: Methylated spirit/water concentrations, lubricant and motor oils and animal red blood cell concentrations. Resonant frequency shifts in the region of 10s of MHz were observed. However most notably in the methylated spirit concentrations there was no resonant frequency shift, only a shift in the return losses were observed. The integration of the E-plane filter and the microfluidic capillary resulted in poor repeatability due to alignment issues of the filter and capillary. The second design incorporates the use of Distributed Bragg Reflectors for a compact and fully integrated, no moving parts, device. The simulation results produced a Q-factor 1,942 at a resonant frequency of 23.3 GHz. The Bragg sensor produced promising simulation results as well as initial experimental results. There was up to 20 MHz resonant frequency shift between the samples. Samples included Eppendorf tubes filled with water and oil

Doctor of Philosophy

dissertationThe terahertz frequency band extends from deep infrared (100 THz) down to millimeter waves (0.4 THz), and this band was mostly inaccessible due to the lack of appropriate sources and detectors. Those with access to this band had to endure the small-intensity pulsed signals (nanowatts to microwatts) that the terahertz sources of those times could provide. In recent years, however, sufficient development has led to the availability of terahertz sources with sufficient power (1-100 μW) and the ease of use these sources has in turn enabled researchers to develop newer sources, detectors, and application areas. The terahertz regime is interesting because a) many molecules have vibrational, rotation and transition absorption bands in this regime, b) the terahertz electromagnetic wavelength is sufficiently small to resolve centimeter to millimeter scale objects, and c) scattering and absorption in metals in the terahertz regime make it very challenging to devise terahertz signal processing circuits. Thus, performing terahertz reflection/transmission measurements may enable precise identification of chemicals in a sample. Furthermore, small wavelengths and strong scattering by metallic objects make imaging with terahertz waves quite attractive. Finally, the ability to devise terahertz communication circuits and links will provide access to a frequency domain that is restricted and not available to others. One of the main objectives of this work is to develop 0.75 - 1.1 terahertz (free space wavelength 272 μm â€" 400 μm) amplifiers. Another objective of this work is to explore the suitability of terahertz waves in biological imaging and sensing. The terahertz amplifiers developed in this work consisted of distributed components such as rectangular waveguides and cylindrical dielectric resonators. In contrast to discrete amplifiers, which are based on solid-state devices, distributed traveling wave amplifiers can potentially handle and produce larger powers. Three different distributed terahertz amplifier circuits were considered in this work. These were based on a) coupled dielectric resonators, b) dielectric waveguides with periodic slots, and c) metallic meandering waveguides. The result of the hot test of the last circuit on interaction with an electron beam energy source yielded an amplification of 12 dB of a -55 dBm, 0.9 terahertz signal over ~1 gigahertz bandwidth. The electron beam acceleration voltage was 4.8 kV and its current was approximately 20 microamps. The terahertz biosensing system developed in this work was used to study the unique interaction of terahertz waves with the chemical and physical components of biological tissues, and the products of biochemical reactions. A terahertz near-field imaging system was also developed to image mouse brain slices, plants, and bug wings. In addition, this work also demonstrated the capabilities and limitations of terahertz waves for the real-time noninvasive monitoring of bioethanol production by yeast cells

Design, Fabrication, and Demonstration of Square Holey Dielectric THZ Waveguides

A variety of novel dielectric THz waveguides were demonstrated to increase a channel capacity in a chip-to-chip communication system. Square holey cladding dielectric THz waveguides were designed, fabricated, and characterized. The single material holey cladding waveguide is low loss and easy to fabricate compared to doped core fibers. The square geometry supports two states of polarization with minimum cross-talk for polarization division multiplexing applications. Simulations show the waveguide supports two states of polarization across the frequency range of 180 GHz to 360 GHz. In addition, simulations show good mode isolation and low bending losses. Holey cladding square waveguide was fabricated using a custom-built draw tower to preserve the square geometry. TOPAS was chosen from several studied dielectrics for its low material loss and fabrication capabilities. Fabricated waveguides were shown to support the mode despite manufacturing defects. Fiber loss measurements showed a 24 dB/m loss that approach the accepted material loss of TOPAS (22 dB/m). THz vortex waveguides were demonstrated for space division multiplexing applications for the first time. The holey cladding TOPAS-based vortex waveguide was designed to preserve orbital angular momentum for l=1 and 2 at 280 GHz. The output power of the waveguide for different l and core sizes were studied. The waveguide was fabricated with the custom-built draw tower. Transmission of a first order OAM beam at 280 GHz was experimentally demonstrated. The first order, l=1, Laguerre-Gaussian beam was generated with a custom-made spiral phase plate. Inspired by the vortex waveguide design, several low-loss square holey core/cladding waveguides were designed and simulated for polarization division multiplexing. The waveguides combine the benefits of low loss and broadband transmission, while supporting two states of polarization. The boundary conditions created by the holey cladding confine the beam to the holey core for a low loss transmission. Three square holey core/cladding designs were proposed. These designs include a single-hole core, a nine-hole core, and a core comprised of four square capillary tubes. The square capillary tubes exhibits 7 dB/m, which is significantly lower than the material loss of TOPAS (22 dB/m)

Microwave and Millimeter-wave Miniaturization Techniques, and Their Applications

Miniaturization is an inevitable requirement for modern microwave and mm-wave circuits and systems. With the emerging of high frequency monolithic integrated circuits, it is the passive components’ section that usually occupies the most of the area. As a result, developing creative miniaturization techniques in order to reduce the physical sizes of passive components while keep their high performance characteristics is demanding. On the other hand, it is the application that defines the importance and effectiveness of the miniaturization method. For example, in commercial handset wireless communication systems, it is the portability that primarily dictates miniaturization. However, in case of liquid sensing applications, the required volume of the sample, cost, or other parameters might impose size limitations. In this thesis, various microwave and mm-wave miniaturization methods are introduced. The methods are applied to various passive components and blocks in different applications to better study their effectiveness. Both componentlevel designs and system-level hybrid integration are benefited from the miniaturization methods introduced in this thesis. The proposed methods are also experimentally tested, and the results show promising potential for the proposed methods