Radar Sub-surface Sensing for Mapping the Extent of Hydraulic Fractures and for Monitoring Lake Ice and Design of Some Novel Antennas.

Hydraulic fracturing, which is a fast-developing well-stimulation technique, has greatly expanded oil and natural gas production in the United States. As the use of hydraulic fracturing has grown, concerns about its environmental impacts have also increased. A sub-surface imaging radar that can detect the extent of hydraulic fractures is highly demanded, but existing radar designs cannot meet the requirement of penetration range on the order of kilometers due to the exorbitant propagation loss in the ground. In the thesis, a medium frequency (MF) band sub-surface radar sensing system is proposed to extend the detectable range to kilometers in rock layers. Algorithms for cross-hole and single-hole configurations are developed based on simulations using point targets and realistic fractured rock models. A super-miniaturized borehole antenna and its feeding network are also designed for this radar system. Also application of imaging radars for sub-surface sensing frozen lakes at Arctic regions is investigated. The scattering mechanism is the key point to understand the radar data and to extract useful information. To explore this topic, a full-wave simulation model to analyze lake ice scattering phenomenology that includes columnar air bubbles is presented. Based on this model, the scattering mechanism from the rough ice/water interface and columnar air bubbles in the ice at C band is addressed and concludes that the roughness at the interface between ice and water is the dominate contributor to backscatter and once the lake is completely frozen the backscatter diminishes significantly. Radar remote sensing systems often require high-performance antennas with special specifications. Besides the borehole antenna for MF band subsurface imaging system, several other antennas are also designed for potential radar systems. Surface-to-borehole setup is an alternative configuration for subsurface imaging system, which requires a miniaturized planar antenna placed on the surface. Such antenna is developed with using artificial electromagnetic materials for size reduction. Furthermore, circularly polarized (CP) waveform can be used for imaging system and omnidirectional CP antenna is needed. Thus, a low-profile planar azimuthal omnidirectional CP antenna with gain of 1dB and bandwidth of 40MHz is designed at 2.4GHz by combining a novel slot antenna and a PIFA antenna.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120674/1/wujf_1.pd

Modelling and Simulation of the Topside Electromagnetic Environment of a Naval Combatant in Concept Design

The topside of a naval combatant must accommodate a plethora of highly sophisticated and computerised electromagnetic sensors in order for the ship to effectively fight, both to attack and defend. The electromagnetic sensors serve as the eyes and ears of the ship, and without them the ship would be very vulnerable. Since the topside of a naval ship has limited space, antennas must be sited close to each other (co-site). Many of the topside antennas are required to transmit and receive at similar bands of operating frequencies and, at times, they may be required to operate simultaneously. This gives rise to electromagnetic interference (EMI) which causes performance degradation of the equipment, blockage of communication channels, impairment of the on board sensors and even burning out of the inadequately protected equipment. One of the key challenges faced by ship designers at the concept phase of ship design is the need to effectively distribute topside electromagnetic (EM) sensors to avoid EMI. This is difficult to predict especially as in concept design the ship configuration and the EM systems characteristics will change as different arrangements are explored. The likely interference between shipboard antenna systems can be assessed by computational electromagnetic (CEM) tools which model the ship and its topside antenna systems. To tackle this problem, a general purpose and commercially available electromagnetic simulation package, Computer Simulation Technology (CST), has been employed as a rapid and cost effective method for handling the EMI problems in Early Stage Ship Design (ESSD). Using CST, the project initially modelled the recently in service Royal Navy Type 22 Batch II Frigate and its topside sensors. The EM sensor models on the Type 22 Batch II Frigate model were then simulated against each other in order to determine the EMI coupling between them. To benchmark these EMI coupling simulations, validation of a certain number of CST simulations has been carried out using two physical scale models of the Type 22 Batch II Frigate. After obtaining the required confidence in the reliability of the simulation package, a CST based approach for prediction of topside EMI/EMC has been developed. The approach has then been 3 applied on an early design study for a Future Patrol Ship to predict the likely EM interactions between its topside antennas. Finally, in order to assess the likely free space antenna interference, MATLAB based codes have been developed. These will allow quick evaluations of the magnitude of antenna interference in free space. Thus, they would enable the project sponsor to determine antenna interactions between certain shipboard EM sensors without requiring to use a CEM tool

Antenna de-­embedding for on­-body communications with wearables and implants

The particular challenge for modeling wearable and implantable wireless systems for on-body communications lies in the near-field coupling of the antenna and the dissipative tissue. Hence, so far, the antennas could not be considered separately from the propagation channel in the system description. Therefore, methods for the systematic antenna design of on-body applications are developed, whereas the antennas are characterized de-embedded. First, a method for characterizing on-body antennas is developed based on physical modeling of the propagation along the tissue. Furthermore, on-body antenna parameters are derived, representing an adapted form of the standard free-space antenna parameters. Secondly, a method for modeling on-body links based on spherical wave functions (SWF) is developed. It enables obtaining separate models of the antennas and the channel at a higher level of abstraction. Since the developed on-body antenna parameters are defined closely to the standard free-space definitions, an intuitive characterization of on-body antennas is possible. Furthermore, an antenna test range is developed for assessing the defined on-body antenna parameters for physical prototypes. As shown by the examples evaluated, the on-body antenna parameters and the determined transmission equation, analogous to the Friis equation in free-space, can also be used to model the entire wireless system. However, the difficulty lies in determining the directional channel model, which is costly and not universally possible for any application. The developed method based on SWF complements the characterization methods, as channels of any complexity can be modeled since the method could be implemented numerically. Beyond the characterization of on-body antennas and channels, the design of optimized antennas for these applications presents a substantial challenge. Based on the derived on-body transmission equation, antenna optimization can be done directly by maximizing the on-body antenna gain in the direction of the main propagation path. For more complex channels, antenna optimization based on SWF modeling is also developed. With this, optimal characteristics of the antenna can be calculated based on many different possible channel models. To also obtain a possibility for validation with measurements here, both developed methods are linked with each other so that a determination of the on-body antenna parameters is also possible based on the optimal SWF coefficients. With several application examples, it has been validated that the developed methods enable efficient de-embedded modeling and educated design of wearable and implanted antennas for on-body communications.Die besondere Herausforderung bei der Modellierung von am Körper getragenen und implantierbaren drahtlosen Systemen liegt in der Nahfeldkopplung der Antenne und des dissipativen Gewebes. Daher konnten bisher die Antennen nicht getrennt vom Ausbreitungskanal in der Systembeschreibung berücksichtigt werden. Aus diesem Grund werden Methoden für die systematische Antennenentwicklung von On-Body-Anwendungen entwickelt, wobei die Antennen separat (de-embedded) charakterisiert werden können. Zunächst wird eine Methode zur Charakterisierung von On-Body-Antennen entwickelt, die auf der physikalischen Modellierung der Ausbreitung entlang des Gewebes basiert. Darüber hinaus wurden On-Body-Antennenparameter abgeleitet, die eine angepasste Form der Standardantennenparameter für den freien Raum darstellen. Desweiteren wird eine Methode zur Modellierung von On-Body-Verbindungen auf Grundlage von sphärischen Wellenfunktionen entwickelt. Diese ermöglicht es, getrennte Modelle der Antennen und des Kanals auf einer höheren Abstraktionsebene zu erhalten. Da die entwickelten On-Body-Antennenparameter in enger Anlehnung an die Standarddefinitionen für den freien Raum definiert sind, ist eine intuitive Charakterisierung von On-Body-Antennen möglich. Weiterhin wird ein Antennenmesssystem entwickelt, um die definierten Antennenparameter für physische Prototypen auswerten zu können. Wie die untersuchten Beispiele zeigen, können die On-Body-Antennenparameter und die ermittelte Übertragungsgleichung, analog zur Friis-Gleichung im Freiraum, auch zur Modellierung des gesamten Funksystems verwendet werden. Die Schwierigkeit liegt hier jedoch in der Bestimmung des Kanalmodells, die aufwändig und nicht für jede Anwendung universell möglich ist. Die entwickelte Methode auf Basis sphärischer Wellenfunktionen (SWF) ergänzt die Charakterisierungsmethoden, da aufgrund der numerischen Implementierung hiermit Kanäle beliebiger Komplexität modelliert werden können. Neben der Charakterisierung von On-Body-Antennen und -Kanälen stellt der Entwurf von optimierten Antennen für diese Anwendungen eine große Herausforderung dar. Mithilfe der abgeleiteten Übertragungsgleichung für On-Body Antennen kann die Antennenoptimierung direkt basierend auf den On-Body Antennenparametern erfolgen, indem der Gewinn der On-Body Antenne in Richtung des Hauptausbreitungspfads maximiert wird. Für komplexere Kanäle wird auch eine Antennenoptimierung auf der Grundlage der SWF-Modellierung entwickelt. Auf diese Weise können die optimalen Eigenschaften der Antenne auf Grundlage vieler verschiedener möglicher Kanalmodelle berechnet werden. Um auch hier eine Möglichkeit zur messtechnischen Validierung zu erhalten, werden beide entwickelten Methoden miteinander verknüpft, sodass eine Bestimmung der On-Body Antennenparameter auch auf Basis der SWF-Koeffizienten möglich ist. Anhand mehrerer Anwendungsbeispiele konnte validiert werden, dass die entwickelten Methoden eine effiziente Modellierung sowie ein fundiertes Design von tragbaren und implantierten Antennen für die On-Body-Kommunikation ermöglichen

UWB Technology

Ultra Wide Band (UWB) technology has attracted increasing interest and there is a growing demand for UWB for several applications and scenarios. The unlicensed use of the UWB spectrum has been regulated by the Federal Communications Commission (FCC) since the early 2000s. The main concern in designing UWB circuits is to consider the assigned bandwidth and the low power permitted for transmission. This makes UWB circuit design a challenging mission in today's community. Various circuit designs and system implementations are published in this book to give the reader a glimpse of the state-of-the-art examples in this field. The book starts at the circuit level design of major UWB elements such as filters, antennas, and amplifiers; and ends with the complete system implementation using such modules

Antenna Designs for 5G/IoT and Space Applications

This book is intended to shed some light on recent advances in antenna design for these new emerging applications and identify further research areas in this exciting field of communications technologies. Considering the specificity of the operational environment, e.g., huge distance, moving support (satellite), huge temperature drift, small dimension with respect to the distance, etc, antennas, are the fundamental device allowing to maintain a constant interoperability between ground station and satellite, or different satellites. High gain, stable (in temperature, and time) performances, long lifecycle are some of the requirements that necessitates special attention with respect to standard designs. The chapters of this book discuss various aspects of the above-mentioned list presenting the view of the authors. Some of the contributors are working strictly in the field (space), so they have a very targeted view on the subjects, while others with a more academic background, proposes futuristic solutions. We hope that interested reader, will find a fertile source of information, that combined with their interest/background will allow efficiently exploiting the combination of these two perspectives

New approaches to probing Minkowski functionals

We generalize the concept of the ordinary skew-spectrum to probe the effect of non-Gaussianity on the morphology of cosmic microwave background (CMB) maps in several domains: in real space (where they are commonly known as cumulant-correlators), and in harmonic and needlet bases. The essential aim is to retain more information than normally contained in these statistics, in order to assist in determining the source of any measured non-Gaussianity, in the same spirit as Munshi & Heavens skew-spectra were used to identify foreground contaminants to the CMB bispectrum in Planck data. Using a perturbative series to construct the Minkowski functionals (MFs), we provide a pseudo-C based approach in both harmonic and needlet representations to estimate these spectra in the presence of a mask and inhomogeneous noise. Assuming homogeneous noise, we present approximate expressions for error covariance for the purpose of joint estimation of these spectra. We present specific results for four different models of primordial non-Gaussianity local, equilateral, orthogonal and enfolded models, as well as non-Gaussianity caused by unsubtracted point sources. Closed form results of nextorder corrections to MFs too are obtained in terms of a quadruplet of kurt-spectra. We also use the method of modal decomposition of the bispectrum and trispectrum to reconstruct the MFs as an alternative method of reconstruction of morphological properties of CMB maps. Finally, we introduce the odd-parity skew-spectra to probe the odd-parity bispectrum and its impact on the morphology of the CMB sky. Although developed for the CMB, the generic results obtained here can be useful in other areas of cosmology

Calculation of stellar electron-capture cross sections on nuclei based on microscopic Skyrme functionals

A fully self-consistent microscopic framework for evaluation of nuclear weak-interaction rates at finite temperature is introduced, based on Skyrme functionals. The single-nucleon basis and the corresponding thermal occupation factors of the initial nuclear state are determined in the finite-temperature Skyrme Hartree-Fock model, and charge-exchange transitions to excited states are computed using the finite-temperature RPA. Effective interactions are implemented self-consistently: both the finite-temperature single-nucleon Hartree-Fock equations and the matrix equations of RPA are based on the same Skyrme energy density functional. Using a representative set of Skyrme functionals, the model is applied in the calculation of stellar electron-capture cross sections for selected nuclei in the iron mass group and for neutron-rich Ge isotopes.Comment: 31 pages, 13 figures, submitted to Physical Review

Electromagnetic Compatibility in Wireline Communications

This document is a thesis submitted in partial fulfilment of the requirements of the University of Hertfordshire for the degree of Doctor of Philosophy (Part Time) in 'EMC in Wire-line Communications' in the School of Electronic, Communication and Electrical Engineering at the University of Hertfordshire. It describes a programme of research into the modelling and measurement of radio frequency interference emissions from various communication networks including Power Line (Tele)communications (PLC/PLT) and Digital Subscriber Line (DSL). An introduction and literature review are followed by the results of practical measurements on installed networks. These measurements include antenna gain and Longitudinal Conversion Loss (LCL). Power line communication networks, splitterless DSL and home phoneline networks in buildings are studied and modelled and the models are compared with the measured results. Improved EMC test methods are also described, in particular the modelling and design of four types of portable antennas for use in radiated EMC measurements with improved sensitivity at frequencies up to 30 MHz. The first type is a set of three manually tuned loop antennas covering 100 kHz - 30 MHz. The second is a set of three loop antennas that cover a similar frequency range but with remote tuning via an optical fibre link, under the control of software which also controls an EMC measuring receiver. The third type is a larger (1.6 m diameter) tuned loop covering 1.75 - 10 MHz that allows the measuring system noise floor to be below the typical atmospheric noise floor. The fourth type is an electrically short dipole covering 10 - 30 MHz with improved matching. The protection requirements for various types of radio communication services are analysed and are compared with emission levels from various types of wireline communication network. A review of existing applicable EMC standards and standards under development is also presented