INANOE Repositorio (Inst- Nacional de Astrofísica, Óptica y Electrónica
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Synthesis and design of CMOS mixers with carrier feed-through cancellation and output power modulation for wireless communication systems
Get PDFThe present work is about the synthesis and design of a passive mixer in CMOS
technology with carrier feed-through cancellation and output power modulation, which
satisfies the demands established by Bluetooth, Ultra Wideband (UWB) and Medical
Implant Communication Service (MICS).
The simulation in Mentor Graphicsr ICstudio 2008:2b of the harmonic mixer
for the Bluetooth and UWB standards with the UMC 0:18µm Mixed Mode and RF
CMOS technology have been carried out. Furthermore, was designed and fabricated a
passive mixer in a double poly three metal layers 0:5µm CMOS technology from MOSIS
foundry for MICS standard. For the proposed designs for the UMC 0:18µm technology
we have two designs, the first is single-ended and second is differential both proposals
have identical performance in Gc with -6:05dB, IIP3 of 15:5dBm and a variation of
the conduction angle from 40% to 7%. However, the differential mixer has an NF of
9:73dB which is superior compared to the NF of 7:7dB of the single-ended mixer; but
the principal advantage of the differential mixer is that it removes all the harmonics
of fLO and increases the dynamic range
Identificación de personas por medio de un conjunto de características en imágenes de nudillos
Get PDFExisten varias aplicaciones reales que promueven el control de acceso de personas
tales como seguridad de ciertas áreas, asistencia, entre otras; es por ello que es de
gran interés la identificación de personas, debido a que es un asunto que se ha venido
abordando de diversas formas y métodos los cuales se han vuelto poco confiables, a
causa de esto se ha estado buscando más alternativas y una de las cuales se propone
para este trabajo es por medio de los nudillos de las manos, logrando de esta forma se
pueda realizar un aporte a la investigación en esta área, que actualmente no es
cuantiosa debido a que lleva pocos años y no existe un estándar que facilite su uso
confiable y repetitivo.
Una de las dificultades que se afrontan para la identificación por medio de nudillos es la
descripción de segmentos de curvas de los mismos a partir de imágenes, es por ello
que se pretenden desarrollar estrategias para explorar una forma novedosa que
contribuya a la relación internudillos e intranudillos. A grandes rasgos se plantea utilizar
el conocimiento en procesamiento de imágenes para resolver una aplicación que está
relacionada con biometría y propiedades de los nudillos por medio de tres bloques
generales como el pre-procesamiento, extracción de características para
representación y clasificación dando una solución al problema propuesto. Se trabajó
con una base de datos de 128 personas, obtenidas en dos sesiones de las cuales se
obtuvieron como resultados 98.7% para la identificación correcta y 1.3% de falsos
positivos
Study of optoelectronic characteristics in Germanium- Silicon films deposited by low frequency plasma and related devices
Get PDFThe thin film photovoltaic devices are considered as a promising alternative to conventional crystalline silicon solar cells because: 1) less material is needed per unit area to fully absorb the visible part of the solar spectrum (i.e., the thin film solar cells need intrinsic films with thickness of around ≈0.3 to fully absorb the visible part of the solar spectrum, whereas the dominant crystalline and polycrystalline silicon solar cells need intrinsic films with thickness of around ≈300), 2) can be fabricated photovoltaic modules of very large area in comparison with crystalline and polycrystalline silicon photovoltaic modules, 3) can be perform fabrication processes at low temperature using a wide variety of substrates (flexible, rigid, metals or insulators), films (contacts, buffers, active films, reflectors, etc.) and semiconductor materials (silicon, germanium, cadmium telluride, etc.) deposited by a variety of deposition techniques (PVD, CVD, ECD, plasma-based, hybrid, etc.), and 4) manufacturing and installation costs are significantly lower. Consequently, a wide variety of these technologies are being developed and marketed, including amorphous silicon, polymorphous silicon, microcrystalline silicon, polycrystalline silicon, silicon-germanium alloys, cadmium-telluride alloys, copper-indium-gallium-selenium alloys, organic materials, etc. These developments have made it necessary a better understand of the physics of the thin film solar cell devices. However, at present there are still many important issues that have not been studied enough
Analysis of electromagnetic and quantum effects on low dimensional MOS transistors
Get PDFOverall, this work introduces experimental and theoretical work that offers the reader an alternative perspective of looking at 28 nm MOSFET electrical performance and modeling.
Chapter 1 introduces an alternative way to produce a negative differential resistance (NDR) effect that is achieved by the non-conventional biasing of a regular 28-nm n-type Metal-Oxide-Semiconductor Field-Effect Transistor (n-MOSFET). It has a controllable peak-to-valley current ratio (PVCR) that goes from about 3.0 up to a room-temperature value of 5.5, which is above the record of 5.3 previously reported on silicon heterostructures [1]. Two bipolar mechanisms working in parallel are demonstrated to occur inside the n-MOSFET, one at the surface and other in the bulk. Thermally activated electrons are injected into the gate contact through the drain-gate overlap, a situation that leads the transistor to the flat-band condition, blocking the surface conduction channel and triggering the NDR effect. I proposed a simple analytical model that correlates very well with experimental data.
Chapter 2 provides a general perspective of the theoretical approaches that can lead to the determination of the charge current through a nano-scaled system from a full quantum mechanical perspective. It exposes the amount of information that, in principle, can be obtained from any physical system and the complications that arise in the determination of the current. The more realistic but still very difficult statistical quantum mechanical approach is briefly presented afterwards. Finally, the Landauer formalism is established as a series of assumptions that render a close-form expression for the current in terms of the probability of transmission.
An analogy between the time-independent Maxwell and Schrödinger equations is developed in Chapter 3. It is applicable to two-dimensional systems with wave-guide (lead) boundary conditions. On the lead boundaries, the third-order boundary conditions for the electric field reduce to the normal derivative of its z-component, adopting the same form of the equivalent boundary conditions for the Schrödinger equation. The total energy and position-dependent potential energy are included in the set of quantities that have an equivalent electromagnetic parameter
Registration of a three-dimensional model of a human head over a scene using color and depth information
Get PDFThe objective of Augmented Reality (AR) is to enhance a user’s perception of an
environment in real life by providing useful additional information. To achieve
this objective, virtual objects must be correctly positioned in a real environment
to improve the sense of coexistence between real and virtual objects.
In medicine, AR has been well received as it has shown great potential when
aiding in diagnosis, surgical planning or surgical procedures because specific
regions can be precisely targeted. The observation of spatial relations between the
virtual objects and the environment are essential in minimally invasive procedures.
Regarding head procedures, a precise registration is of utmost importance. Even
though there has been research in this area, further investigation can lead to
invaluable discoveries.
When using low-cost computer vision systems, the aligning task becomes
difficult because of excess noise. Using the scene’s depth information obtained
from low-cost range sensors has shown good results; however, these results are
still far from being dependable for the medical field.
This thesis addresses the issue of registering a virtual model with a human
head where images are acquired from two different sources. The first one is an
X-Ray Computed Tomography (CT) scan of the head which is used to create
a three-dimensional (3D) virtual model. The second is the augmented scene,
obtained through a low-cost range sensor taking advantage of depth information.
The proposed method aims at reducing registration errors between the 3D virtual
model of the head and the one in the real world scene.
Our method involves a series of segmentation processes to bound the region
of interest, a preliminary head pose estimation which serves as a basis for the next
step, and a final pose refinement through the Iterative Closest Point algorithm
in order to reach the goal of precise alignment of a human head within a virtual
environment.
We tested the registration results of the proposed method against the registration
of other approaches found in literature addressing the same problem and
using low-cost computer vision systems. For evaluation, we built a new database
which was manually labeled with the transformation values to align the model
with a scene. The reliability of the database was evaluated using an inter-rater
reliability test in order to check the agreement of the raters
Representación de formas articuladas por medio de grafos pesados basados en esqueletos
Get PDFPartiendo de la noción de que el cerebro humano puede reconocer imágenes haciendo
uso únicamente de las siluetas de los objetos, han surgido líneas de investigación interesadas
en abstraer información de la forma de los mismos. Los dos enfoques principales
para el reconocimiento de formas son: basados en contorno y basados en esqueleto. Los
métodos basados en esqueleto han demostrado ser más útiles que los basados en contorno
cuando los objetos son formas articuladas. Sin embargo, aunque existen diferentes métodos
para la construcción de esqueletos a partir de formas 2D, estos métodos requieren
de diferentes parámetros de entrada los cuales son sensibles a las características de las
formas o requieren demasiado tiempo de ejecución. Por otra parte, aunque son numerosos
los métodos para la obtención de esqueletos a partir de formas, son pocos los trabajos que
presentan estrategias para la obtención de características a partir de los esqueletos, de tal
manera que puedan ser utilizadas en tareas de identificación, clasificación y reconocimiento
de formas.
En esta tesis se propone un nuevo método para la obtención de esqueletos sin pérdida
de ramas importantes y libre de ramas no deseadas. Posteriormente, son construidos grafos
pesados a partir de características obtenidas desde el esqueleto y éstos son a su vez
utilizados en tareas de clasificación.
El método de clasificación propuesto en este trabajo utiliza OSB (del inglés Optimal
Subsequence Bijection) para obtener un valor de similitud en función de las correspondencias
encontradas entre pares de pixeles finales para dos esqueletos representados como
grafos pesados. La estrategia de clasificación propuesta en este trabajo permite una alta
reducción del costo computacional y produce mejores resultados de clasificación respecto
a métodos presentados en la literatura que utilizan OSB para comparar grafos
A study of stellar orbits in a logarithmic non axisymmetric rotating potential
Get PDFIn this thesis a study of the theoretical foundations of stellar orbits in non axisymmetric
rotating potentials has been made. Before to get into the study of
orbits integrated numerically, the linear theory was studied. In this approximation
the non-axisymmetry of a potential is taken as a first order perturbation.
Using this approximation, the called characteristic curves were built analytically
using an isochrone potential. In that way, it was understood how orbits that
have been integrated in an inertial frame, closes in a rotating frame to form a
characteristic curve.
Specifically the GALI2 index and the shooting method were applied in order
to build the characteristic curves numerically. These characteristic curves were
constructed for a logarithmic potential keeping the pattern speed equal to the
unity and varying the axial ratio with values q = 1, q = 0.8, and q = 0.4. The
system of differential equations were integrated numerically for 10 Gyrs and our
integrator keeps the error in the energy below 10−12 order.
In the axisymmetric case (q = 1) all the families of orbits are stable, therefore
they keep their morphology for 10 Gyr. In the non-axisymmetric cases it is
found that the non-axisymmetry induces chaos on the characteristic curve and
some families disappear. The X1 family is found at q = 0.8 and q = 0.4. In both
cases this family is stable at lower energies, but some of its members are unstable
at higher energies. The stable members of the X1 family are the backbones of
the bar structure
Identificación y modelado de resonancias en la transmisión de señales en substratos anisotrópicos
Get PDFLas líneas de transmisión tipo stripline, presentan más de una resonancia
cerca de las frecuencias en las que múltiplos de media longitud de onda de las
señaales que se propagan, igualan la separación entre las fibras tejidas a lo largo
de su recorrido dentro de una tarjeta de circuito impreso. Estas resonancias
tienen un efecto que impacta negativamente el rendimiento de las interconexiones
en alta frecuencia.
En este trabajo, se presenta un análisis exhaustivo acerca del origen de
dichas resonancias. Además, es propuesta una metodología para la implementación
del circuito equivalente de striplines y un método analítico que permite
la obtención de su constante de propagación efectiva e impedancia característica,
incluyendo este efecto no deseado. Ambos modelos, consideran la presencia
de cargas periódicas en la línea y las representan como capacitores, es por esto
que como parte del estudio realizado, también se propone un método para la
determinación del valor de estos capacitores, empleando datos experimentales.
Con el fin de validar las propuestas realizadas, se comparan los resultados
obtenidos de las simulaciones de circuito equivalente, y los datos obtenidos de
manera analítica con mediciones realizadas hasta 50 GHz a striplines fabricadas
en materiales comerciales
The multipath fading and the frequency response of the channel in an indoor radiating cable system
Get PDFThe use of wireless handheld devices has increased in recent years, at the same time; the data transmission rate rises exponentially. This trend has led to a greater concentration of mobile devices in specific locations, such as office buildings, shopping centers, airports, sports stadiums, etc. In this context, the next generation of wireless services must be able to develop ubiquitous ultra-broadband speeds. Hence, solutions are required for overcoming the hurdles present at these locations in order to satisfy the user requirements. In this regard, dedicated systems are an alternative for providing wireless services at indoor environments, while also allowing performance improvement and the possibility of offering tailored services for specific environments. In this context, radiating cables have been used as alternative distribution systems for indoor environments where distributed antenna systems have limitations giving full coverage due to obstacles (walls, doors, furniture, etc.) between the receiver and transmitter. Such scenarios generate challenges on the study and design of these radiating cable systems – for example, issues involved in the wireless communication channel
Parameter-varying lowpass filters based on switched-capacitor circuits
Get PDFIn some applications, filtering circuits whose response have a short transient time
are necessary. In the classical approach of filter design, the designer has no much
options to manipulate the filter characteristics in the time domain because the design
formulae affects the frequency-domain specifications. Parameter-varying filters
posses as a chief characteristic their short transient time duration, which makes them
suitable for applications in which speed is a mandatory need. The short transient is
the result of a temporary variation of one or more of their descriptive parameters.
Despite this advantageous feature, that has been demonstrated with solid theoretical
analyses, there is still a bottle-neck in the practical implementation of these kinds of
filters.
In this work, an implementation of a parameter-varying filter based on switchedcapacitors
(SC) is presented. This implementation is a second-order low pass SC
filter on a FPAA (Field-Programmable Analog Array) development board. Theoretical
aspects related to this implementation are reported, in particular stability
and homogeneous response analysis. Experimental results of the parameter-varying
implemented filter are presented and compared with the time-invariant counterpart.
In summary, the theoretical analysis and the experimental results support the
feasibility of implementing parameter-varying filters with switched-capacitor techniques