abstract: A proposed visible spectrum nanoscale imaging method requires material with permittivity values much larger than those available in real world materials to shrink the visible wavelength to attain the desired resolution. It has been proposed that the extraordinarily slow propagation experienced by light guided along plasmon resonant structures is a viable approach to obtaining these short wavelengths. To assess the feasibility of such a system, an effective medium model of a chain of Noble metal plasmonic nanospheres is developed, leading to a straightforward calculation of the waveguiding properties. Evaluation of other models for such structures that have appeared in the literature, including an eigenvalue problem nearest neighbor approximation, a multi- neighbor approximation with retardation, and a method-of-moments method for a finite chain, show conflicting expectations of such a structure. In particular, recent publications suggest the possibility of regions of invalidity for eigenvalue problem solutions that are considered far below the onset of guidance, and for solutions that assume the loss is low enough to justify perturbation approximations. Even the published method-of-moments approach suffers from an unjustified assumption in the original interpretation, leading to overly optimistic estimations of the attenuation of the plasmon guided wave. In this work it is shown that the method of moments approach solution was dominated by the radiation from the source dipole, and not the waveguiding behavior claimed. If this dipolar radiation is removed the remaining fields ought to contain the desired guided wave information. Using a Prony's-method-based algorithm the dispersion properties of the chain of spheres are assessed at two frequencies, and shown to be dramatically different from the optimistic expectations in much of the literature. A reliable alternative to these models is to replace the chain of spheres with an effective medium model, thus mapping the chain problem into the well-known problem of the dielectric rod. The solution of the Green function problem for excitation of the symmetric longitudinal mode (TM01) is performed by numerical integration. Using this method the frequency ranges over which the rod guides and the associated attenuation are clearly seen. The effective medium model readily allows for variation of the sphere size and separation, and can be taken to the limit where instead of a chain of spheres we have a solid Noble metal rod. This latter case turns out to be the optimal for minimizing the attenuation of the guided wave. Future work is proposed to simulate the chain of photonic nanospheres and the nanowire using finite-difference time-domain to verify observed guided behavior in the Green's function method devised in this thesis and to simulate the proposed nanosensing devices. / Dissertation/Thesis / M.S. Electrical Engineering 2013

abstract: With increasing demand for System on Chip (SoC) and System in Package (SiP) design in computer and communication technologies, integrated inductor which is an essential passive component has been widely used in numerous integrated circuits (ICs) such as in voltage regulators and RF circuits. In this work, soft ferromagnetic core material, amorphous Co-Zr-Ta-B, was incorporated into on-chip and in-package inductors in order to scale down inductors and improve inductors performance in both inductance density and quality factor. With two layers of 500 nm Co-Zr-Ta-B films a 3.5X increase in inductance and a 3.9X increase in quality factor over inductors without magnetic films were measured at frequencies as high as 1 GHz. By laminating technology, up to 9.1X increase in inductance and more than 5X increase in quality factor (Q) were obtained from stripline inductors incorporated with 50 nm by 10 laminated films with a peak Q at 300 MHz. It was also demonstrated that this peak Q can be pushed towards high frequency as far as 1GHz by a combination of patterning magnetic films into fine bars and laminations. The role of magnetic vias in magnetic flux and eddy current control was investigated by both simulation and experiment using different patterning techniques and by altering the magnetic via width. Finger-shaped magnetic vias were designed and integrated into on-chip RF inductors improving the frequency of peak quality factor from 400 MHz to 800 MHz without sacrificing inductance enhancement. Eddy current and magnetic flux density in different areas of magnetic vias were analyzed by HFSS 3D EM simulation. With optimized magnetic vias, high frequency response of up to 2 GHz was achieved. Furthermore, the effect of applied magnetic field on on-chip inductors was investigated for high power applications. It was observed that as applied magnetic field along the hard axis (HA) increases, inductance maintains similar value initially at low fields, but decreases at larger fields until the magnetic films become saturated. The high frequency quality factor showed an opposite trend which is correlated to the reduction of ferromagnetic resonant absorption in the magnetic film. In addition, experiments showed that this field-dependent inductance change varied with different patterned magnetic film structures, including bars/slots and fingers structures. Magnetic properties of Co-Zr-Ta-B films on standard organic package substrates including ABF and polyimide were also characterized. Effects of substrate roughness and stress were analyzed and simulated which provide strategies for integrating Co-Zr-Ta-B into package inductors and improving inductors performance. Stripline and spiral inductors with Co-Zr-Ta-B films were fabricated on both ABF and polyimide substrates. Maximum 90% inductance increase in hundreds MHz frequency range were achieved in stripline inductors which are suitable for power delivery applications. Spiral inductors with Co-Zr-Ta-B films showed 18% inductance increase with quality factor of 4 at frequency up to 3 GHz. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

Orientador: Hugo Enrique Hernandez Figueroa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-05T08:31:54Z (GMT). No. of bitstreams: 1 Ambrosio_LeonardoAndre_M.pdf: 2415252 bytes, checksum: c4357386bcd33e0676d894544a47c85e (MD5) Previous issue date: 2005 / Resumo: Este trabalho apresenta um modelo numérico baseado no método das diferenças finitas no domínio do tempo, com objetivo de analisar as características da taxa de absorção específica, SAR, na cabeça humana, mediante um modelamento quiral das equações de Maxwell. A formulação é expressa em termos dos campos polarizados elétrico e magnético, permitindo investigar possíveis variações de SAR na cabeça humana, para diferentes valores de quiralidade, através de algoritmos simples. Tais algoritmos tornam possíveis a análise das diversas características da SAR em estruturas bidimensionais, representando secções transversais da cabeça humana, discretizada em seus tecidos de volumes significativos. Uma verificação foi feita calculando se a estabilidade numérica e simulando uma fonte pontual em um meio quiral. As influências da impedância equivalente da antena e da distância entre a antena e a cabeça humana foram investigadas, para diferentes valores quirais, bem como é feita a análise da SAR local média e sua variação percentual para os valores quirais escolhidos. Cinco cortes transversais foram analisados, com o objetivo de verificar características e comportamentos globais de SAR, evitando assim que variações locais fossem assumidas como um efeito global / Abstract: This work shows a numerical model based on the finite-difference time-domain method, with the aim of analysing the characteristics of the Specific Absorption Rate, SAR, in a human-head, through a quiral modeling of Mawell¿s equations. The formulation is expressed in terms of the electric and magnetic wave-fields, allowing to investigate possible changes in SAR, inside the human head, for different values of chirality, using simple algorithms. Such algorithms, make the analysis of the several characteristics of SAR in bidimensional structures representing the transversal layers of the human head, discretized in its tissues possessing significant volumes. A verification was made by calculating the numerical punctual stability and by simulating a punctual source in a chiral medium. The influences of the equivalent impedances of the antenna and of the distance between the antenna and the human head are analysed, for different chiral values, as well as an analysis of the average local SAR and its percentual variation for chosen chiral values. Five transversal layers were analysed, with the aim of verifying global characteristics and behaviors of SAR, avoiding that local variations were assumed as a global effect / Mestrado / Telecomunicações / Mestre em Engenharia Elétrica

Orientador: Hugo Enrique Hernandez Figueroa, Michel zamboni Rached / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T09:52:49Z (GMT). No. of bitstreams: 1 Ambrosio_LeonardoAndre_D.pdf: 7134713 bytes, checksum: 36a77f1e2e7f49fb16e793969325d64e (MD5) Previous issue date: 2009 / Resumo: Nesta tese, abordamos aplicações de feixes localizados em FSO - Free Space Optics - e em pinças ópticas, com ênfase maior para o segundo. No primeiro caso, mostramos que é possível pré-determinar o padrão de intensidade longitudinal através de elementos ópticos adequadamente modelados em suas funções de fase: os áxicons. Assim, estes feixes poderiam ser usados para alinhar o link. No caso de pinças ópticas, exploramos a idéia de que, em breve, será possível a contrução de partículas esféricas homogêneas, na escala micrométrica, com índice de refração negativo (as chamadas DNG particles, ou Double-Negative particles), e verificamos as propriedades de aprisionamento óptico tanto para feixes gaussianos quanto para feixes localizados, no regime de óptica geométrica e no caso mais geral da teoria eletromagnética. A idéia de que partículas são atraídas para regiões de alta intensidade quando seu índice de refração é maior do que o do meio, e para regiões de baixa intensidade quando este índice é menor, embora válida para partículas convencionais - aquelas com índice de refração positivo -, deve ser revista para partículas DNG. / Abstract: In this thesis, we explore some applications of localized beams in FSO - Free Space Optics - and optical tweezers, greater emphasis been given to the second one. For FSO, we show that it is possible to choose the desired longitudinal intensity pattern by using optical elements adequately modeled in their phase functions: the axicons. In this way, these beams could be uses for optical alignment of the link. In the case of optical tweezers, we investigate the possibility that it will soon be possible to design and build homogeneous spherical particles, in the micron scale, with negative refractive index (the so called DNG particles, or Double-Negative particles), and we verify some properties related to optical trapping, both for Gaussian and Bessel beams, in the optics ray regime and in the more general electromagnetic case. The idea that particles with refractive index higher than the medium in which it is immersed is attracted to regions of high intensity, whereas it is attracted to regions of low intensity when its refractive index is lower than the medium, although valid for conventional particles - those with positive refractive index - must be revisited for DNG particles. / Doutorado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Various facets of direct digital manufactured (DDM) microwave packages are studied. The rippled surface inherent in fused deposition modeling (FDM) fabricated geometries is modeled in Ansoft HFSS, and its effect on the performance of microstrip transmission lines is assessed via simulation and measurement. The thermal response of DDM microstrip transmission lines is analyzed over a range of RF input powers, and linearity is confirmed over that range. Two IC packages are embedded into DDM printed circuit boards, and their performance is analyzed. The first is a low power RF switch, and the second is an RF front end device that includes a low noise amplifier (LNA) and a power amplifier (PA). The RF switch is shown to perform well, as compared to a layout designed for a Rogers 4003C microwave laminate substrate. The LNA performs within datasheet specifications. The power amplifier generates substantial heat, so a thermal management attempt is described. Finally, a capacitively loaded 6dB Wilkinson power divider is designed and fabricated using DDM techniques and materials. Its performance is analyzed and compared to simulation. The device is shown to compare favorably to a similar device fabricated on a Rogers 4003C microwave laminate using traditional printed circuit board techniques.

Reconfigurable radio frequency (RF) devices are attractive for miniaturization of wireless components and systems by handling functionality of multiple distinct devices. Existing reconfiguration techniques rely on device loadings with semiconductor diodes, ferrite/ferroelectric materials, and microelectromechanical system (MEMS) switches and capacitors. However, it is well-recognized that these techniques cannot fully address important system metrics such as high efficiency, wide frequency tuning range, high power handling capability and cost. Therefore, novel alternative techniques are highly desirable to advance the state of the art in reconfigurable RF devices. The aim of this dissertation is to investigate the novel concept of microfluidically loaded reconfigurability within the context of RF antennas and imaging systems. The proposed devices operate based on continuously movable microfluidic loads consisting of metal (liquid/solid) and dielectric solutions. Microfluidics and microfabrication techniques are utilized with flexible/rigid multilayered substrates to maximize the reconfigurable loading effect on the devices and enable highly reconfigurable antennas and imaging array realizations. Specifically, a wideband frequency tunable monopole antenna is introduced by utilizing continuously movable liquid metal within the microfluidic channel as a length varying conductor. By resorting to ultra-thin channel walls, the liquid metal volume overlapping with the microstrip line feed is utilized as a non-radiating capacitive excitation point to achieve the realized 4:1 (1.29GHz – 5.17GHz) frequency tuning range. Subsequently, an alternative design that replaces liquid metal volume with a microfluidically movable metallized plate is introduced. This novel liquid-metal-free implementation alleviates the liquid metal associated drawbacks of reliability, long-term device operation, and efficiency. The antenna is shown to provide 2:1 (1.6GHz – 3.5GHz) frequency tuning range with > 87 % radiation efficient. Due to the high radiation efficiency, the antenna is also capable of handling 15 W of RF power which is 10 W more than its liquid metal counterpart. This metallized plate approach is also suitable for reconfiguration of miniature antennas, and this is demonstrated with the design/implementation of a microfluidically reconfigurable top loaded monopole antenna. It is also suitable for reconfiguration of other structures such as textile antennas – and this is demonstrated with a 0.8GHz to 1.4GHz frequency reconfigurable textile antenna realization. The last section of the dissertation introduces a novel surface imaging array realization by utilizing the microfluidically reconfigurable metallized plate as an RF read-out circuit component. Specifically, a 24 element imaging array is designed and validated to operate within 6 – 12 GHz band with subwavelength resonators to demonstrate the possibility of constructing low-cost high-resolution microwave surface imaging arrays by utilizing the microfluidics based reconfiguration techniques. The presented work emphasizes system level implementation of the proposed devices by integrating them with micropump units, controller boards, and investigating their reliability performances under higher power RF excitations.

The method of moment (MoM) [1] is a widely used method in electromagnetics to solve static and dynamic electromagnetic problems on varying geometries. However, in closely spaced geometries coupled with large aspect ratios, e.g. a large parallel plate capacitor with very small separation gap, the problem exhibits several challenges. Firstly, the close proximity of the field and source elements presents problems with convergence in numerical evaluations of the interactions between them. Secondly, the aspect ratio of the geometry gives an approximation whereby to far field points, the source contributions from locations that are far apart appear to cancel each other. This leads to high condition numbers in the system matrix. This thesis explores the potential solution to these problems as well as the application of modular fast and direct (MFD) [2] solver to expedite the solution of such problems.

Approved for public release; distribution is unlimited / The Numerical Electromagnetics Code (NEC) was used to evaluate the admittance, average power gain, and the electric near and far field of a monopole antenna mounted on a cubical box over a perfectly conducting ground plane. Two models of the box, employing surface patches and wire grids, were evaluated. The monopole was positioned at the center, the edge, and at a corner of the box's top surface. Admittance and average power gain of the antenna were calculated. NEC results were examined and compared with experimental data and with results from "PATCH", another independent electromagnetic modeling code. The near electric field was calculated for both models. Computer graphics techniques were presented for plotting NEC near field results using DISSPLA (Display Integrated Software System and Plotting Language), a commercial graphics package. Contour and 3-D amplitude, and phase plots of the near electric fields were presented. Radiation patterns were calculated to relate far field and near field behavior of the antenna. Surface patch and wire grid models are compared and conclusions were presented. / Naval Ocean Systems Center / http://archive.org/details/investigationofn00elli / O&MN, Direct Funding / Lieutenant, Hellenic Navy

Radio Frequency (RF) filters are among the key components of today’s multifunctional devices and test equipment. However, the multifuctionality need significantly drives the required filter number and causes large areas to be allocated for filters. To alleviate this issue, over the recent years, reconfigurable filters have been proposed as an attractive alternative. Nevertheless, existing reconfigurable filter technologies demonstrate degraded performances in terms of loss, frequency tunability bandwidth, and power handling capability. This work investigates, for the first time, microfluidic based reconfiguration techniques for implementation of RF bandpass filters. Specifically, microfluidics is shown to provide mechanisms for achieving compact RF bandpass filters that can exhibit low loss, high power handling, and high frequency tunability. First, we present the utilization of liquid metals for realization of a frequency-agile microstrip bandpass filters consisting of broadside coupled split ring resonator (BC-SRR). In this design approach, one of the loops of the BC-SRR is realized from liquid metal to be able to microfluidically change the resonator shape and associated resonance frequency. The filter exhibits a 29% frequency tunable range from 870 MHz to 650 MHz, with insertion loss <3 >dB, over the entire frequency tuning range, for a fractional bandwidth (FBW) of 5%. To the best of our knowledge, this filter design is the first in available literature that shows a continuously frequency reconfigurable microfluidic RF band-pass filter. To overcome the oxidization and lower conductivity issues associated with liquid metals and enhance the frequency tuning range further, subsequently, we introduce a filter design technique in which microfluidically repositionable metallized plates are utilized within microfluidic channels with ultra-thin insulator walls. Specifically, this technique is employed to design a two pole microstrip bandpass filter where microfluidically repositionable metalized plates are used to capacitively load printed open loop resonators. To operate the filter (and control movement of multiple metalized plates) with a single bi-directional micropump unit, a strategically designed meandered microfluidic channel is implemented. The filter exhibits a 50% tuning range (from 1.5 GHz to 0.9 GHz), with an insertion loss15 W input power without the need of thick ground planes and/or heat sinks.

Silicon photonics is a very promising technology for future low-cost high-bandwidth optical telecommunication applications down to the chip level. This is due to the high degree of integration, high optical bandwidth and large speed coupled with the development of a wide range of integrated optical functions. Silicon-based microring resonators are a key building block that can be used to realize many optical functions such as switching, multiplexing, demultiplaxing and detection of optical wave. The ability to tune the resonances of the microring resonators is highly desirable in many of their applications. In this work, the study and application of a thermally wavelength-tunable photonic switch based on silicon microring resonator is presented. Devices with 10µm diameter were systematically studied and used in the design. Its resonance wavelength was tuned by thermally induced refractive index change using a designed local micro-heater. While thermo-optic tuning has moderate speed compared with electro-optic and all-optic tuning, with silicon’s high thermo-optic coefficient, a much wider wavelength tunable range can be realized. The device design was verified and optimized by optical and thermal simulations. The fabrication and characterization of the device was also implemented. The microring resonator has a measured FSR of ~18 nm, FWHM in the range 0.1-0.2 nm and Q around 10,000. A wide tunable range (>6.4 nm) was achieved with the switch, which enables dense wavelength division multiplexing (DWDM) with a channel space of 0.2nm. The time response of the switch was tested on the order of 10 us with a low power consumption of ~11.9mW/nm. The measured results are in agreement with the simulations. Important applications using the tunable photonic switch were demonstrated in this work. 1×4 and 4×4 reconfigurable photonic switch were implemented by using multiple switches with a common bus waveguide. The results suggest the feasibility of on-chip DWDM for the development of large-scale integrated photonics. Using the tunable switch for output wavelength control, a fiber laser was demonstrated with Erbium-doped fiber amplifier as the gain media. For the first time, this approach integrated on-chip silicon photonic wavelength control.