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This book describes a new, extremely low frequency (ELF)/ very low frequency (VLF) miniaturized transmitter concept, based on the mechanical motion of permanent magnets or electrets. The authors explain how utilizing the very high energy density of modern ferromagnetic and ferroelectric materials, such “electromechanical transmitters’’ can provide much higher field generation efficiency than conventional antennas, thus enabling practical ELF/VLF wireless communications links. The text begins with the fundamental challenges of such links and provides an historical overview of the attempts that have been made to address these challenges. It then focuses on the design and implementation of practical electromechanical ELF/VLF transmitters, which is an interdisciplinary subject that spans multiple research areas including electromagnetics, power electronics, control systems, and mechanical design. The authors also describe how such transmitters can be combined with receivers and signal processing algorithms to realize complete ELF/VLF links in challenging environments.
ELF/VLF radio signals, from approximately 300Hz to 30KHz, are commonly used for submarine communications, ionospheric remote sensing, geophysical prospecting, and studies of the near-Earth space environment. Naturally occurring ELF/VLF emissions caused by nearly every lightning strike can be detected for thousands of miles and provide an abundance of wave-particle interaction possibilities in the radiation belts. Any applied studies of these events, however, require electromagnetic waves in the ELF/VLF band to be amplified, captured, analyzed, and stored. Specific studies often require the placement of receivers in extremely remote locations such as Antarctica or the middle of an ocean, and are almost always located far away from power sources to decrease noise. These scientific requirements drive the creation of new ELF/VLF receiver systems. Two new receiver systems were designed for use in terrestrial, typically Antarctic, locations. Both new systems utilize 10-100 times less power than the lowest-power comparable existing ELF/VLF receivers and were designed for remote unmanned operation in extreme environments without external power. The so called Penguin system, comprised of a hybrid microcontroller and FPGA architecture, removes the overhead of a general purpose CPU to provide the most streamlined processing for data acquisition possible while still maintaining a relatively traditional sampling architecture. The drastically reduced architecture of the Penguin system, compared to traditional receiver systems, on average consumes less power than a typical LED indicator lamp while capturing high fidelity ELF/VLF magnetic field snapshots every fifteen minutes. The low power and thermal requirements of the Penguin system enables low-cost remote studies of medium to large timescale phenomena such as Chorus and Auroral Hiss without the need for local power. The system has been deployed and operated at the United States Amundsen Scott South Pole Station in Antarctica. A second ELF/VLF receiver architecture, the VLF Advanced Technology platform, or "VAT", removes the typical CPU from the sampling and recording loop further reducing power requirements and physical system size while gaining the ability to record continuously. This radically new architecture enables future scientific studies of the fine structure in time and frequency of long-term events, such as the onset mechanisms of natural Chorus emissions, due to the extremely low power requirements. The system architecture is also greatly applicable to any continuous time recording system, including but not limited to acoustic and electromagnetic arrays for subsurface imaging systems, ionospheric remote sensing, and optical sensors.
Recent emphasis upon the importance of the physical environment has made science and the public even more cog nizant of the many components of the biosphere. While much attention has been given to ionizing electromagnetic stimuli which causes blatant and unalterable changes in biological systems, relatively little research has been concerned with those electromagnetic signals whose frequencies overlap with time-varying processes in living organisms. Extremely low frequency (ELF) electromagnetic fields can occur as waves between about I Hz to 100 Hz or as short pulses within this range of very low frequency (VLF) and higher frequency sources. The natural occurrence of ELF signals is associated with weather changes, solar disturbances and geophysical ionospheric perturbations. Man-made sources have also been reported. Certain physical properties of ELF signals make them excellent candidates for biologically important stimuli. Unlike many other weather components, ELF signals have the capacity to penetrate structures which house living organ isms. ELF wave configurations allow long distance propaga tional capacities without appreciable attenuation of inten sity, thus making them antecedent stimuli to approaching weather changes. Most importantly, ELF signals exhibit the frequencies and wave forms of bio-electrical events that occur within the brain and body. Thus resonance inter actions between animal and nature become attractive possi bilities.
Based on the author's PhD thesis, this book is a theoretical study of subterranean radio communication, with the focus on methods that depend primarily on the penetration of electromagnetic fields through the ground. Through-the-earth communication using e-m fields - specifically magnetic induction - plays a role in search and rescue systems used in the mining industry. It is also used for borehole telemetry, pipeline location and by cavers and pot-holers. Chapters describe propagation, antennas, and the design of transmitters and receivers. A figure of merit - the specific aperture - is introduced as an aid to antenna design. A crucial aspect of all systems is the signal to noise ratio, for which the strategy of noise-matching is introduced. The design of a wide-band low-frequency sounder is described, for channel evaluation using a non-ideal binary sequence. A method of calculating the inverse of a generalised sequence is described, for which cross-correlation results in a system identification signal.
Thorough coverage of basic digital communication system principles ensures that readers are exposed to all basic relevant topics in digital communication system design. The use of CD player and JPEG image coding standard as examples of systems that employ modern communication principles allows readers to relate the theory to practical systems. Over 180 worked-out examples throughout the book aids readers in understanding basic concepts. Over 480 problems involving applications to practical systems such as satellite communications systems, ionospheric channels, and mobile radio channels gives readers ample opportunity to practice the concepts they have just learned. With an emphasis on digital communications, Communication Systems Engineering, Second Edition introduces the basic principles underlying the analysis and design of communication systems. In addition, this book gives a solid introduction to analog communications and a review of important mathematical foundation topics. New material has been added on wireless communication systems—GSM and CDMA/IS-94; turbo codes and iterative decoding; multicarrier (OFDM) systems; multiple antenna systems. Includes thorough coverage of basic digital communication system principles—including source coding, channel coding, baseband and carrier modulation, channel distortion, channel equalization, synchronization, and wireless communications. Includes basic coverage of analog modulation such as amplitude modulation, phase modulation, and frequency modulation as well as demodulation methods. For use as a reference for electrical engineers for all basic relevant topics in digital communication system design.
Includes author and subject indexes.
This book presents high-quality papers from the Seventh Asia International Symposium on Mechatronics (AISM 2019). It discusses the latest technological trends and advances in electromechanical coupling and environmental adaptability design for electronic equipment, sensing and measurement, mechatronics in manufacturing and automation, micro-mechatronics, energy harvesting & storage, robotics, automation and control systems. It includes papers based on original theoretical, practical and experimental simulations, development, applications, measurements, and testing. The applications and solutions discussed here provide excellent reference material for future product developments.
This thoroughly revised textbook provides a description of current networking technologies and protocols as well as important new tools for network performance analysis based on queuing theory. The third edition adds topics such as network virtualization and new related architectures, novel satellite systems (such as Space X, OneWeb), jitter and its impact on streaming services, packet level FEC techniques and network coding, new Markovian models, and advanced details on M/G/1 queuing models. The author also adds new selected exercises throughout the chapters and a new version of the slides and the solution manual. The book maintains its organization with networking technologies and protocols in Part I and then theory and exercises with applications to the different technologies and protocols in Part II. This book is intended as a textbook for master level courses in networking and telecommunications sectors.