A Novel Method for Tuning a Transistor-Based non-Foster Matching Circuit for Electrically Small Wideband Antennas

This dissertation reviews the application of non-Foster circuits for wideband antenna matching, and introduces a novel, rapid means of “tuning” the circuit to accommodate variations in antenna loadings. The tuning is accomplished via the judicious addition of a common transistor.A detailed literature search is provided, and non-Foster circuits are discussed in detail, including the myriad of implementations with focus on tuning. A comparison between different tuning methods is presented. The novel tuning method is evaluated via the normalized determinant function to ensure stability. Evaluations include simulations using commercially available software and experimentation to ensure not only stability but also that noise added by the active circuitry is manageable. Wideband stable operation is confirmed by pairing the tunable non-Foster matching circuit with an electrically small, resistively loaded dipole, and performance gains are demonstrated using the tunability feature. The resistively loaded dipole alone demonstrates reasonable performance at higher frequencies, but performance degrades considerably at lower frequencies, when the dipole is electrically small. The tunable non-Foster circuit is shown to alleviate some of this degradation. Additionally, applications other than wideband antenna matching can benefit from tunable non-Foster circuits such as tunable filters and phase shifters, and these are discussed as well. Finally, practical limitations of non-Foster circuits are presented

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Design strategies for electrically small antennas, actively matched with non-foster elements

Mención Internacional en el título de doctorDuring the last years, some researchers have been working on active matching or on non-Foster matching networks for electrically small antennas (ESAs), in response to the vertiginous increase in demand for compact devices working in multiband platforms. The inclusion of non- Foster networks allows broad bandwidths at lower frequencies, overcoming the inherent limitations derived from the high-quality factor (Q) property of ESAs. Thus, the development of multiband antennas with an engineered lower broadband obtained by embedding an active non- Foster matching network (MN) is one of the primary objectives addressed in this work. Such non-Foster MNs are implemented by using Negative Impedance Converters (NICs), introduced many years ago to realize negative capacitors or negative inductors that disobey the Foster's reactance theorem. In this sense, an integral design methodology of actively matched ESAs with embedded non-Foster elements is proposed and developed. This design method takes into account the operating parameters inherent to a radiating element, such as efficiency and radiation pattern, impedance matching, realizability, and stability. A new parameter (called Sens) on the sensitivity of the ESA when loaded with a non-Foster form is introduced. This sensitivity analysis will allow us to choose not only the kind of antennas that can be properly matched with non-Foster networks but also the most suitable position of such networks into the antenna structure, in order to optimize the performance of the design. The design methodology can be easily extended to any type of antenna, disregarding its electrical size. Two electrically small antennas are presented as design examples in which the proposed design strategy is applied. First, a printed small semiloop antenna, which is resonant at 1200 MHz, is loaded with an embedded MOSFET-based NIC, resulting in a new lower-band with a fractional bandwidth (FBW) of 119% (centered at 117 MHz). Second, a blade-type monopole, whose resonant frequency is around 300 MHz, is loaded with an embedded non-Foster MN, resulting in a new working band whose FBW of 82% (centered at 85 MHz). The notable results in terms of impedance bandwidth and miniaturization level encouraged us to keep seeking for solutions for radiation pattern changes and added noise issues. Finally, the proposed design strategy is applied to fewelement antenna arrays to obtain a multiband performance, keeping unchanged the natural response of the host structure (i.e. around its resonant frequency).Durante los últimos años, algunos investigadores han venido trabajando en la inclusión de redes de adaptación tipo non-Foster en antenas eléctricamente pequeñas (Electrically Small Antennas, ESA). Esto en respuesta a la creciente demanda de dispositivos compactos, que funcionen a diferentes bandas de frecuencia, como parte de los modernos sistemas y plataformas multibanda. La consecución de sistemas compactos y de banda ancha, así como la obtención de múltiples frecuencias de trabajo han sido uno de los objetivos primarios de la presente tesis doctoral. La inclusión de estructuras non-Foster, que reciben este nombre debido a que no obedecen a las propiedades establecidas por el teorema de R. M. Foster en 1924, permite el ensanchamiento de la banda de adaptación de impedancia o la obtención de una banda adicional para una misma estructura radiante. Dentro de los circuitos más representativos de las redes non-Foster se encuentran los Convertidores de Impedancia Negativa (Negative Impedance Converter, NIC), comúnmente implementados con transistores, a través de los cuales es posible la implementación de inductores o de condensadores “negativos”. La realización de una impedancia “negativa” por medio de un NIC, es de vital importancia en la adaptación de la impedancia de antena en banda ancha que se busca en este trabajo. En este sentido, se hace necesario establecer una metodología de diseño de este tipo de antenas, que tenga en cuenta los parámetros de funcionamiento inherentes a un elemento radiante, como son: eficiencia y diagrama de radiación, adaptación de impedancias, factibilidad y estabilidad. Esto, a través del análisis de la sensibilidad a la ubicación de puertos (propuesto en este proyecto), análisis de estabilidad del sistema completo (antena y red de adaptación activa), análisis de distribución de corrientes etc., hace que la estrategia de diseño que se pretende desarrollar y describir pueda resultar una herramienta realmente útil en el diseño de las mencionadas antenas. El parámetro de sensibilidad, Sens, introducido en este trabajo, otorga al diseñador un criterio de selección cuantitativo con respecto a qué tipo de antena puede, en efecto, ser adaptada con elementos non-Foster y la posición misma de _estos dentro de la estructura. De este modo, el parámetro Sens constituye una herramienta de optimización del desempeño del sistema radiante diseñado. Adicionalmente, cabe mencionar que la metodología de diseño propuesta y desarrollada en esta tesis puede ser aplicada a cualquier tipo de antena, sin importar su naturaleza ni su tamaño en términos eléctricos. Luego de desarrollada y descrita la metodología |estrategia| de diseño, se presentan dos antenas eléctricamente pequeñas a manera de ejemplos de diseño. La primera consiste en un semilazo impreso sobre un dieléctrico, resonante a 1200 MHz, cargado con un NIC compuesto de transistores MOSFET. Como resultado, se obtiene una nueva banda de trabajo cuyo ancho de banda de adaptación relativo (FBW) es de 119% (centrado en 117 MHz). La segunda antena ejemplo consiste en un monopolo ensanchado, tipo aleta (blade-monopole), en cuya estructura es embebida una red de adaptación activa, basada también en transistores MOSFET. En este segundo caso, se obtuvo una banda adicional con un FBW de 82% (centrado en 85 MHz). Los notables resultados en términos de adaptación de impedancia y de nivel de miniaturización de las estructuras radiantes, alentaron al autor a continuar con la búsqueda de alternativas de solución a los cambios en el diagrama de radiación observados y a el nivel de ruido adicionado por la red activa embebida. Finalmente, la estrategia de diseño descrita es aplicada a arreglos (arrays) de antenas de pocos elementos, en busca de obtener un comportamiento multibanda en el que la banda incluida comprenda frecuencias a las que toda la estructura es eléctricamente pequeña.Programa Oficial de Doctorado en Multimedia y ComunicacionesPresidente: Milos Mazánek.- Secretario: Luis Enrique García Muñoz.- Vocal: Marco A. Antoniade

Broken passivity and time-reversal-symmetry bounds in acoustics devices

We collect information about the world through our senses, two of which, hearing and touch, are attuned to the mechanical vibrations travelling around us. Scientists and engineers have learned to control these acoustic waves, and in so doing they have opened new possibilities in how we interact with each other and the natural world. One area of rapid progress is acoustic metamaterials, which are architected structures that can shape sound waves in ways that go beyond what is possible with natural materials. Given the potential of these new materials, it is important to consider their limits and identify the underlying physical principles responsible for them. In this dissertation we examine limitations in the response of acoustic materials and devices due to passivity and time-reversal symmetry. An important constraint that arises due to time-reversal symmetry is reciprocity. Reciprocity must be broken to create devices that allow sound through in only one direction. This work explores acoustic nonreciprocity with particular attention to applications in surface acoustic wave devices and topological acoustic demonstrations. One way to achieve acoustic nonreciprocity is with fluid flow. Based on this technique, we present an acoustic Mach-Zehnder isolator and nonreciprocal leaky-wave antenna. A different but equally fundamental and important constraint in acoustics technology is the trade-off between the size, efficiency, and bandwidth of a small resonator. By considering arbitrary stored and radiated sound fields surrounding a compact source, we derive a theoretical lower bound on the quality factor of a passive acoustic radiator. This work discusses opportunities to overcome this constraint by considering active resonators. We experimentally demonstrate a three-fold bandwidth improvement to the passive case by synthesizing a non-Foster circuit load for a piezoelectric sonar transducer. By using a Green’s function approach and by connecting the physics of a disordered array to the statistical theory of random walks, we also explore the physics of near-zero-index materials, and leverage their unusual sound-matter interactions to enable robust and highly directive acoustic sources. This work introduces an entirely new way to achieve highly directional sound beyond traditional techniques.Mechanical Engineerin

Navigation and guidance requirements for commercial VTOL operations

The NASA Langley Research Center (LaRC) has undertaken a research program to develop the navigation, guidance, control, and flight management technology base needed by Government and industry in establishing systems design concepts and operating procedures for VTOL short-haul transportation systems in the 1980s time period. The VALT (VTOL Automatic Landing Technology) Program encompasses the investigation of operating systems and piloting techniques associated with VTOL operations under all-weather conditions from downtown vertiports; the definition of terminal air traffic and airspace requirements; and the development of avionics including navigation, guidance, controls, and displays for automated takeoff, cruise, and landing operations. The program includes requirements analyses, design studies, systems development, ground simulation, and flight validation efforts

Injection matching of antenna

One of the most important modules of the current and next generation of the wireless communications is the antenna. The coexistence of the machine and human in the next communication system will open-up a vast range of new applications and communication services which need to be supported by the antenna. Moreover, the forthcoming 5G technology vision is prognosticated on the use of multiple communication bands and standards in a seamless fashion.This can force the mobile devices to have multiple antennas on a single device which will add significant complexity or using an antenna with wideband reconfiguration capability. On the other hand, switched-off analogue communications provides the opportunity for re-using prime spectrum in UHF bands. Considering the size of hand-held devices, this will need strong miniaturization. To address these requirements, electrically small, tunable, wideband and highly efficient antenna technology is strongly desired. In this thesis a new area of research in antenna design is introduced which has been unexplored by the other researchers. A new theory called Injection Matching Theory (IMT) is proposed which uses multi-port configuration. This will enable to control current distribution on the antenna structure at its extremities and couple a wave length, much larger than what the antenna dimensions naturally allow. Apart from electrically small operation this can be used for improving band width and efficiency, and providing reconfiguration capability. To illustrate the versatility of the proposed theory, for every feature mentioned above a chapter is provided which demonstrates the potential capability of the proposed theory via simulation and fabrication of the prototyped examples

Useful applications of earth-oriented satellites - Navigation and traffic control

Use of satellites for navigation and traffic contro

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium