FMCW Signals for Radar Imaging and Channel Sounding

A linear / stepped frequency modulated continuous wave (FMCW) signal has for a long time been used in radar and channel sounding. A novel FMCW waveform known as “Gated FMCW” signal is proposed in this thesis for the suppression of strong undesired signals in microwave radar applications, such as: through-the-wall, ground penetrating, and medical imaging radar. In these applications the crosstalk signal between antennas and the reflections form the early interface (wall, ground surface, or skin respectively) are much stronger in magnitude compared to the backscattered signal from the target. Consequently, if not suppressed they overshadow the target’s return making detection a difficult task. Moreover, these strong unwanted reflections limit the radar’s dynamic range and might saturate or block the receiver causing the reflection from actual targets (especially targets with low radar cross section) to appear as noise. The effectiveness of the proposed waveform as a suppression technique was investigated in various radar scenarios, through numerical simulations and experiments. Comparisons of the radar images obtained for the radar system operating with the standard linear FMCW signal and with the proposed Gated FMCW waveform are also made. In addition to the radar work the application of FMCW signals to radio propagation measurements and channel characterisation in the 60 GHz and 2-6 GHz frequency bands in indoor and outdoor environments is described. The data are used to predict the bit error rate performance of the in-house built measurement based channel simulator and the results are compared with the theoretical multipath channel simulator available in Matlab

MC64-Cluster: Many-Core CPU Cluster Architecture and Performance Analysis in B-Tree Searches

The MC64-Cluster computer platform was designed, based on many-core CPU microprocessors: Tile64. MC64-Cluster architecture was outlined in terms of both hardware and software, including commands available to manage jobs and provided application programming interfaces to communicate and synchronize tiles, making this system easy to use. Massively, concurrent-searches of keys in B-trees, which are used in many applications, including bioinformatics, were used. Remarkable performance improvements were obtained when the cluster resources were combined with those available in host machine (hybrid or heterogeneous environments). These results were even more outstanding when analyzed in terms of performance-per-watt, highlighting their green-computing advantages. Together with the cluster architecture, they represent the main contributions of this work. To our knowledge, this is the first cluster implementation of this kind being developed

Advanced Techniques for Ground Penetrating Radar Imaging

Ground penetrating radar (GPR) has become one of the key technologies in subsurface sensing and, in general, in non-destructive testing (NDT), since it is able to detect both metallic and nonmetallic targets. GPR for NDT has been successfully introduced in a wide range of sectors, such as mining and geology, glaciology, civil engineering and civil works, archaeology, and security and defense. In recent decades, improvements in georeferencing and positioning systems have enabled the introduction of synthetic aperture radar (SAR) techniques in GPR systems, yielding GPR–SAR systems capable of providing high-resolution microwave images. In parallel, the radiofrequency front-end of GPR systems has been optimized in terms of compactness (e.g., smaller Tx/Rx antennas) and cost. These advances, combined with improvements in autonomous platforms, such as unmanned terrestrial and aerial vehicles, have fostered new fields of application for GPR, where fast and reliable detection capabilities are demanded. In addition, processing techniques have been improved, taking advantage of the research conducted in related fields like inverse scattering and imaging. As a result, novel and robust algorithms have been developed for clutter reduction, automatic target recognition, and efficient processing of large sets of measurements to enable real-time imaging, among others. This Special Issue provides an overview of the state of the art in GPR imaging, focusing on the latest advances from both hardware and software perspectives

Analysis and solutions for RFID tag and RFID reader deployment in wireless communications applications. Simulation and measurement of linear and circular polarised RFID tag and reader antennas and analysing the tags radiation efficiency when operated close to the human body.

The aim of this study is to analysis, investigate and find out the solutions for the problems associated with the implementations of antennas RFID Reader and Tag for various applications. In particular, the efficiency of the RFID reader antenna and the detection range of the RFID tag antenna, subject to a small and compact antenna¿s design configuration have been studied. The present work has been addressed directly to reduce the cost, size and increase the detection range and communication reliability of the RFID framework antennas. Furthermore, the modelling concept of RFID passive tags mounted on various materials including the novel design of RFID reader antenna using Genetic Algorithm (GA) are considered and discussed to maintain reliable and efficient antenna radiation performances. The main benefit of applying GA is to provide fast, accurate and reliable solutions of antenna¿s structure. Therefore, the GA has been successfully employed to design examples: meander-line, two linear cross elements and compact Helical- Spiral antennas. In addition, a hybrid method to model the human body interaction with RFID tag antenna operating at 900MHz has been studied. The near field distribution and the radiation pattern together with the statistical distribution of the radiation efficiency and the absorbed power in terms of cumulative distribution functions for different orientation and location of RFID¿s tag antenna on the human body have been demonstrated. Several tag antennas wi th symmetrical and unsymmetrical structure configurations operating in the European UHF band 850-950 MHz have been fabricated and tested. . The measured and simulated results have been found to be in a good agreement with reasonable impedance matching to the typical input impedance of an RFID integrated circuit chip and nominal power gain and radiation patterns

Phonon polariton interaction with patterned materials

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2008.Vita.Includes bibliographical references (p. 139-144).The generation, propagation and detection of THz phonon polaritons are studied through both femtosecond pump-probe techniques, and Finite Difference Time Domain (FDTD) simulations in this thesis. The theory surrounding the driving, propagation and detection of these modes is treated in a consistent notational system for both analytical solutions and approximate simulated responses. FDTD simulations in one, two and three dimensions are designed to best mimic lab experimental parameters, with various approximations of both THz pumping and probing developed. Various improvements on the FDTD method with the goal of more rapid simulations and more accurately described simulations of lab experiments from generation to detection are considered and developed. Experiments on phonon-polaritons interacting with periodicity and confinement in one, two, and three dimensions are all considered, and methods of data processing developed. By comparing FDTD simulation results to experimental results, the full three dimensional fields within these crystals can be investigated, and in many cases fully defined. The methods demonstrated open up new possibilities for THz spectroscopy in waveguides, microfluidics, and related platforms that include THz generation, propagation, interaction with the sample material, and detection in a compact, integrated structure. The methods also enable the proper description of large-amplitude THz generation and applications in nonlinear THz spectroscopy. Finally, linear and nonlinear THz signal processing applications my exploit the experimental and modeling methods described in this thesis.by Eric R. Statz.Ph.D

Evaluation of optical solder for fiber-to-waveguide coupling in silicon photonics

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Includes bibliographical references (leaves 57-59).Copper interconnects have shown its limit to meet the bandwidth demand even in the short reach applications due to its increase power consumption, RC delay, EMI, crosstalk and other effects which are aggravated as dimension shrinks. Despite efforts to increase the system performance, e.g. by multicore technology, migration to photonics is unavoidable, as it can give much superior performance. The major impediment to the wide-use of photonics is the cost. Three major components that contribute to the cost escalation are the absence of integrable light source, fast modulator, and effective fiber to waveguide coupler. The latest issue was addressed in this work. Coupling light efficiently from fiber to waveguide is challenging because of the size (6[mu]m core diameter for fiber, 500nm for waveguide), shape, and refractive index (~1.5 for fiber, 3.5 for waveguide) differences. Optical solder was proposed as the gap filler in between the fiber and waveguide to account for the fabrication uncertainties. Together with an inverse taper structure patterned in the waveguide end, the coupling loss was much reduced from 7.5dB (direct butt-coupling), to less than IdB. Besides, optical solder increases the reliability of device, as it prevents moisture and dust from impairing the optically active area of the die. Its fabrication is also integrable with the current CMOS technology. The configuration allows high density optical interconnect at the edges of the die; together with the electrical interconnect spreading across the area of the chip. All these make this system very good potential coupling method to solve one of the major impediments above, and thus enable the widespread use of electronic-photonic ICs.by Fidelia Tjioe.M.Eng

Aerocapture Systems Analysis for a Titan Mission

Performance projections for aerocapture show a vehicle mass savings of between 40 and 80%, dependent on destination, for an aerocapture vehicle compared to an all-propulsive chemical vehicle. In addition aerocapture is applicable to multiple planetary exploration destinations of interest to NASA. The 2001 NASA In-Space Propulsion Program (ISP) technology prioritization effort identified aerocapture as one of the top three propulsion technologies for solar system exploration missions. An additional finding was that aerocapture needed a better system definition and that supporting technology gaps needed to be identified. Consequently, the ISP program sponsored an aerocapture systems analysis effort that was completed in 2002. The focus of the effort was on aerocapture at Titan with a rigid aeroshell system. Titan was selected as the initial destination for the study due to potential interest in a follow-on mission to Cassini/Huygens. Aerocapture is feasible, and the performance is adequate, for the Titan mission and it can deliver 2.4 times more mass to Titan than an all-propulsive system for the same launch vehicle