Matching Items (12)

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Coffee Can Radar Antenna Redesign for SAR Applications

Description

The purpose of this project is to analyze the MIT OpenCourseWare coffee can radar design and modify it to be better suited for drone based synthetic aperture radar (SAR) applications

The purpose of this project is to analyze the MIT OpenCourseWare coffee can radar design and modify it to be better suited for drone based synthetic aperture radar (SAR) applications while maintaining the low-cost aspect of the original design. The MIT coffee can radar can function as a ranged radar, a Doppler radar, or as SAR. Through simulations and research, the suggestions for how to modify the radar resulted in swapping the coffee can monopole antennas for patch antenna arrays or helical ordinary end-fire antennas, adding an Arduino for automatic recording of output pulses, and switching from a breadboard construction to a PCB to shrink form factor and keep costs and construction time low.

Contributors

Agent

Created

Date Created
  • 2020-12

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Around the Corner Imaging: Developing a Graphical User Interface

Description

This Creative Project was carried out in coordination with the capstone project, Around the Corner Imaging with Terahertz Waves. This capstone project deals with a system designed to implement Around

This Creative Project was carried out in coordination with the capstone project, Around the Corner Imaging with Terahertz Waves. This capstone project deals with a system designed to implement Around the Corner, or Non Line-of-Sight (NLoS) Imaging. This document discusses the creation of a GUI using MATLAB to control the Terahertz Imaging system. The GUI was developed in response to a need for synchronization, ease of operation, easy parameter modification, and data management. Along the way, many design decisions were made ranging from choosing a software platform to determining how variables should be passed. These decisions and considerations are discussed in this document. The resulting GUI has measured up to the design criteria and will be able to be used by anyone wishing to use the Terahertz Imaging System for further research in the field of Around the Corner or NLoS Imaging.

Contributors

Created

Date Created
  • 2019-05

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Holographic Metasurface Leaky Wave Antennas

Description

Articially engineered two-dimensional materials, which are widely known as

metasurfaces, are employed as ground planes in various antenna applications. Due to

their nature to exhibit desirable electromagnetic behavior, they are also used

Articially engineered two-dimensional materials, which are widely known as

metasurfaces, are employed as ground planes in various antenna applications. Due to

their nature to exhibit desirable electromagnetic behavior, they are also used to design

waveguiding structures, absorbers, frequency selective surfaces, angular-independent

surfaces, etc. Metasurfaces usually consist of electrically small conductive planar

patches arranged in a periodic array on a dielectric covered ground plane. Holographic

Articial Impedance Surfaces (HAISs) are one such metasurfaces that are capable of

forming a pencil beam in a desired direction, when excited with surface waves. HAISs

are inhomogeneous surfaces that are designed by modulating its surface impedance.

This surface impedance modulation creates a periodical discontinuity that enables a

part of the surface waves to leak out into the free space leading to far-eld radia-

tion. The surface impedance modulation is based on the holographic principle. This

dissertation is concentrated on designing HAISs with

Desired polarization for the pencil beam

Enhanced bandwidth

Frequency scanning

Conformity to curved surfaces

HAIS designs considered in this work include both one and two dimensional mod-

ulations. All the designs and analyses are supported by mathematical models and

HFSS simulations.

Contributors

Agent

Created

Date Created
  • 2017

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Applications of kinetic inductance: parametric amplifier & phase shifter, 2DEG coupled co-planar structures & microstrip to slotline transition at RF frequencies

Description

Kinetic inductance springs from the inertia of charged mobile carriers in alternating electric fields and it is fundamentally different from the magnetic inductance which is only a geometry dependent property.

Kinetic inductance springs from the inertia of charged mobile carriers in alternating electric fields and it is fundamentally different from the magnetic inductance which is only a geometry dependent property. The magnetic inductance is proportional to the volume occupied by the electric and magnetic fields and is often limited by the number of turns of the coil. Kinetic inductance on the other hand is inversely proportional to the density of electrons or holes that exert inertia, the unit mass of the charge carriers and the momentum relaxation time of these charge carriers, all of which can be varied merely by modifying the material properties. Highly sensitive and broadband signal amplifiers often broaden the field of study in astrophysics. Quantum-noise limited travelling wave kinetic inductance parametric amplifiers offer a noise figure of around 0.5 K ± 0.3 K as compared to 20 K in HEMT signal amplifiers and can be designed to operate to cover the entire W-band (75 GHz – 115 GHz).The research cumulating to this thesis involves applying and exploiting kinetic inductance properties in designing a W-band orthogonal mode transducer, quadratic gain phase shifter with a gain of ~49 dB over a meter of microstrip transmission line. The phase shifter will help in measuring the maximum amount of phase shift ∆ϕ_max (I) that can be obtained from half a meter transmission line which helps in predicting the gain of a travelling wave parametric amplifier. In another project, a microstrip to slot line transition is designed and optimized to operate at 150 GHz and 220 GHz frequencies, that is used as a part of horn antenna coupled microwave kinetic inductance detector proposed to operate from 138 GHz to 250 GHz. In the final project, kinetic inductance in a 2D electron gas (2DEG) is explored by design, simulation, fabrication and experimentation. A transmission line model of a 2DEG proposed by Burke (1999), is simulated and verified experimentally by fabricating a capacitvely coupled 2DEG mesa structure. Low temperature experiments were done at 77 K and 10 K with photo-doping the 2DEG. A circuit model of a 2DEG coupled co-planar waveguide model is also proposed and simulated.

Contributors

Agent

Created

Date Created
  • 2016

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Experimental Evaluation of the Feasibility of Wearable Piezoelectric Energy Harvesting

Description

Technological advances in low power wearable electronics and energy optimization techniques

make motion energy harvesting a viable energy source. However, it has not been

widely adopted due to bulky energy harvester designs

Technological advances in low power wearable electronics and energy optimization techniques

make motion energy harvesting a viable energy source. However, it has not been

widely adopted due to bulky energy harvester designs that are uncomfortable to wear. This

work addresses this problem by analyzing the feasibility of powering low wearable power

devices using piezoelectric energy generated at the human knee. We start with a novel

mathematical model for estimating the power generated from human knee joint movements.

This thesis’s major contribution is to analyze the feasibility of human motion energy harvesting

and validating this analytical model using a commercially available piezoelectric

module. To this end, we implemented an experimental setup that replicates a human knee.

Then, we performed experiments at different excitation frequencies and amplitudes with

two commercially available Macro Fiber Composite (MFC) modules. These experimental

results are used to validate the analytical model and predict the energy harvested as a function

of the number of steps taken in a day. The model estimates that 13μWcan be generated

on an average while walking with a 4.8% modeling error. The obtained results show that

piezoelectricity is indeed a viable approach for powering low-power wearable devices.

Contributors

Agent

Created

Date Created
  • 2020

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Skin tissue terahertz imaging for fingerprint biometrics

Description

Fingerprints have been widely used as a practical method of biometrics authentication or identification with a significant level of security. However, several spoofing methods have been used in the last

Fingerprints have been widely used as a practical method of biometrics authentication or identification with a significant level of security. However, several spoofing methods have been used in the last few years to bypass fingerprint scanners, thus compromising data security. The most common attacks occur by the use of fake fingerprint during image capturing. Imposters can build a fake fingerprint from a latent fingerprint left on items such as glasses, doorknobs, glossy paper, etc. Current mobile fingerprint scanning technology is incapable of differentiating real from artificial fingers made from gelatin molds and other materials. In this work, the adequacy of terahertz imaging was studied as an alternative fingerprint scanning technique that will enhance biometrics security by identifying superficial skin traits. Terahertz waves (0.1 – 10 THz) are a non-ionizing radiation with significant penetration depth in several non-metallic materials. Several finger skin features, such as valley depth and sweat ducts, can possibly be imaged by employing the necessary imaging topology. As such, two imaging approaches 1) using quasi-optical components and 2) using near-field probing were investigated. The numerical study is accomplished using a commercial Finite Element Method tool (ANSYS, HFSS) and several laboratory experiments are conducted to evaluate the imaging performance of the topologies. The study has shown that terahertz waves can provide high spatial resolution images of the skin undulations (valleys and ridges) and under certain conditions identify the sweat duct pattern.

Contributors

Agent

Created

Date Created
  • 2017

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Combination of mmWave imaging and communications for simultaneous localization and mapping

Description

In this thesis, the synergy between millimeter-wave (mmWave) imaging and wireless communications is used to achieve high accuracy user localization and mapping (SLAM) mobile users in an uncharted environment. Such

In this thesis, the synergy between millimeter-wave (mmWave) imaging and wireless communications is used to achieve high accuracy user localization and mapping (SLAM) mobile users in an uncharted environment. Such capability is enabled by taking advantage of the high-resolution image of both line-of-sight (LoS) and non-line-of-sight (NLoS) objects that mmWave imaging provides, and by utilizing angle of arrival (AoA) and time of arrival (ToA) estimators from communications. The motivations of this work are as follows: first, enable accurate SLAM from a single viewpoint i.e., using only one antenna array at the base station without any prior knowledge of the environment. The second motivation is the ability to localize in NLoS-only scenarios where the user signal may experience more than one reflection until it reaches the base station. As such, this proposed work will not make any assumptions on what region the user is and will use mmWave imaging techniques that will work for both near and far field region of the base station and account for the scattering properties of mmWave. Similarly, a near field signal model is developed to correctly estimate the AoA regardless of the user location.

This SLAM approach is enabled by reconstructing the mmWave image of the environment as seen by the base station. Then, an uplink pilot signal from the user is used to estimate both AoA and ToA of the dominant channel paths. Finally, AoA/ToA information is projected into the mmWave image to fully localize the user. Simulations using full-wave electromagnetic solvers are carried out to emulate an environment both in the near and far field. Then, to validate, an experiment carried in laboratory by creating a simple two-dimensional scenario in the 220-300 GHz range using a synthesized 13-cm linear antenna array formed by using vector network analyzer extenders and a one-dimensional linear motorized stage that replicates the base station. After taking measurements, this method successfully reconstructs the image of the environment and localize the user position with centimeter accuracy.

Contributors

Agent

Created

Date Created
  • 2019

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GaN-on-Si RF switched mode power amplifiers for non-constant envelope signals

Description

This work implements three switched mode power amplifier topologies namely inverse class-D (CMCD), push-pull class-E and inverse push-pull class-E, in a GaN-on-Si process for medium power level (5-10W) femto/pico-cells base-station

This work implements three switched mode power amplifier topologies namely inverse class-D (CMCD), push-pull class-E and inverse push-pull class-E, in a GaN-on-Si process for medium power level (5-10W) femto/pico-cells base-station applications. The presented power amplifiers address practical implementation design constraints and explore the fundamental performance limitations of switched-mode power amplifiers for cellular band. The designs are analyzed and compared with respect to non-idealities like finite on-resistance, finite-Q of inductors, bond-wire effects, input signal duty cycle, and supply and component variations. These architectures are designed for non-constant envelope inputs in the form of digitally modulated signals such as RFPWM, which undergo duty cycle variation. After comparing the three topologies, this work concludes that the inverse push-pull class-E power amplifier shows lower efficiency degradation at reduced duty cycles. For GaN based discrete power amplifiers which have less drain capacitance compared to GaAs or CMOS and where the switch loss is dominated by wire-bonds, an inverse push-pull class-E gives highest output power at highest efficiency. Push-pull class-E can give efficiencies comparable to inverse push-pull class-E in presence of bondwires on tuning the Zero-Voltage Switching (ZVS) network components but at a lower output power. Current-Mode Class-D (CMCD) is affected most by the presence of bondwires and gives least output power and efficiency compared to other two topologies. For systems dominated by drain capacitance loss or which has no bondwires, the CMCD and push-pull class-E gives better output power than inverse push-pull class-E. However, CMCD is more suitable for high breakdown voltage process.

Contributors

Agent

Created

Date Created
  • 2015

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Instrument design and radiation pattern testing for terahertz astronomical instruments

Description

The Milky Way galaxy is a powerful dynamic system that is highly efficient at recycling material. Stars are born out of intergalactic gas and dust, fuse light elements into heavier

The Milky Way galaxy is a powerful dynamic system that is highly efficient at recycling material. Stars are born out of intergalactic gas and dust, fuse light elements into heavier elements in their cores, then upon stellar death spread material throughout the galaxy, either by diffusion of planetary nebula or by explosive events for high mass stars, and that gas must cool and condense to form stellar nurseries. Though the stellar lifecycle has been studied in detail, relatively little is known about the processes by which hot, diffuse gas ejected by dying stars cools and conglomerates in the interstellar medium (ISM). Much of this mystery arises because only recently have instruments with sufficient spatial and spectral resolution, sensitivity, and bandwidth become available in the terahertz (THz) frequency spectrum where these clouds peak in either thermal or line emission. In this dissertation, I will demonstrate technology advancement of instruments in this frequency regime with new characterization techniques, machining strategies, and scientific models of the spectral behavior of gas species targeted by these instruments.

I begin this work with a description of radiation pattern measurements and their use in astronomical instrument characterization. I will introduce a novel technique to measure complex (phase-sensitive) field patterns using direct detectors. I successfully demonstrate the technique with a single pixel microwave inductance detectors (MKID) experiment. I expand that work by measuring the APEX MKID (A-MKID) focal plane array of 880 pixel detectors centered at 350 GHz. In both chapters I discuss the development of an analysis pipeline to take advantage of all information provided by complex field mapping. I then discuss the design, simulation, fabrication processes, and characterization of a circular-to-rectangular waveguide transformer module integrated into a circularly symmetric feedhorn block. I conclude with a summary of this work and how to advance these technologies for future ISM studies.

Contributors

Agent

Created

Date Created
  • 2018

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Design of a Cubesat Based Radio Receiver to Detect the Global EoR Signature

Description

The universe since its formation 13.7 billion years ago has undergone many changes. It began with expanding and cooling down to a temperature low enough for formation of atoms of

The universe since its formation 13.7 billion years ago has undergone many changes. It began with expanding and cooling down to a temperature low enough for formation of atoms of neutral Hydrogen and Helium gas. Stronger gravitational pull in certain regions caused some regions to be denser and hotter than others. These regions kept getting denser and hotter until they had centers hot enough to burn the hydrogen and form the first stars, which ended the Dark Ages. These stars did not live long and underwent violent explosions. These explosions and the photons from the stars caused the hydrogen gas around them to ionize. This went on until all the hydrogen gas in the universe was ionized. This period is known as Epoch Of Reionization. Studying the Epoch Of Reionization will help understand the formation of these early stars, the timeline of the reionization and the formation of the stars and galaxies as we know them today. Studying the radiations from the 21cm line in neutral hydrogen, redshifted to below 200MHz can help determine details such as velocity, density and temperature of these early stars and the media around them.

The EDGES program is one of the many programs that aim to study the Epoch of Reionization. It is a ground-based project deployed in Murchison Radio-Astronomy Observatory in Western Australia. At ground level the Radio Frequency Interference from the ionosphere and various man-made transmitters in the same frequency range as the EDGES receiver make measurements, receiver design and extraction of useful data from received signals difficult. Putting the receiver in space can help majorly escape the RFI. The EDGES In Space is a proposed project that aims at designing a receiver similar to the EDGES receiver but for a cubesat.

This thesis aims at designing a prototype receiver that is similar in architecture to the EDGES low band receiver (50-100MHz) but is significantly smaller in size (small enough to fit on a PCB for a cubesat) while keeping in mind different considerations that affect circuit performance in space.

Contributors

Agent

Created

Date Created
  • 2019