Download or read book Modern HF Signal Detection and Direction Finding written by Jay R. Sklar and published by MIT Press. This book was released on 2018-09-25 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: Detailed descriptions of detection, direction-finding, and signal-estimation methods, using consistent formalisms and notation, emphasizing HF antenna array sensing applications. Adaptive antenna array technology encompasses many powerful interference suppression approaches that exploit spatial differences among signals reaching a radio receiver system. Today, worldwide propagation phenomenology occurring in the High Frequency (HF) radio regime has made such interference common. In this book, Jay Sklar, a longtime researcher at MIT Lincoln Laboratory, presents detailed descriptions of detection, direction-finding, and signal-estimation methods applicable at HF, using consistent formalisms and notation. Modern electronic system technology has made many of these techniques affordable and practical; the goal of the book is to offer practicing engineers a comprehensive and self-contained reference that will encourage more widespread application of these approaches. The book is based on the author's thirty years of managing MIT Lincoln Laboratory work on the application of adaptive antenna array technologies to the sensing of HF communication signals. After an overview of HF propagation phenomenology, communication signal formats, and HF receiver architectural approaches, Sklar describes the HF propagation environment in more detail; introduces important modulation approaches and signaling protocols used at HF; discusses HF receiver system architectural features; and addresses signal processor architecture and its implementation. He then presents the technical foundation for the book: the vector model for a signal received at an adaptive array antenna. He follows this with discussions of actual signal processing techniques for detection and direction finding, including specific direction-finding algorithms; geolocation techniques; and signal estimation.
Download or read book Radio Direction Finding and Superresolution written by P. J. D. Gething and published by IET. This book was released on 1991 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: Enlarged and revised second edition. Modern direction finders, capable of measuring elevation angles as well as azimuth angles on the components of multi-ray wavefields, have become powerful tools for research in ionospheric physics and HF radio propagation. The complexity of the problem of resolving closely-spaced rays requires the combined use of wide aperture antenna arrays, multichannel receiving systems and sophisticated digital processing techniques.
Download or read book Transmitter Hunting written by Joseph D. Moell and published by McGraw Hill Professional. This book was released on 1987-06-22 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains all the information needed to set up and perform radio direction finding on HF and VHF bands.
Download or read book Radio Direction Finding written by United States. Department of the Army and published by . This book was released on 1977 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radio Direction Finding written by David William Watson and published by . This book was released on 1971 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Artificial Intelligence written by David R. Martinez and published by MIT Press. This book was released on 2024-06-11 with total page 581 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first text to take a systems engineering approach to artificial intelligence (AI), from architecture principles to the development and deployment of AI capabilities. Most books on artificial intelligence (AI) focus on a single functional building block, such as machine learning or human-machine teaming. Artificial Intelligence takes a more holistic approach, addressing AI from the view of systems engineering. The book centers on the people-process-technology triad that is critical to successful development of AI products and services. Development starts with an AI design, based on the AI system architecture, and culminates with successful deployment of the AI capabilities. Directed toward AI developers and operational users, this accessibly written volume of the MIT Lincoln Laboratory Series can also serve as a text for undergraduate seniors and graduate-level students and as a reference book. Key features: In-depth look at modern computing technologies Systems engineering description and means to successfully undertake an AI product or service development through deployment Existing methods for applying machine learning operations (MLOps) AI system architecture including a description of each of the AI pipeline building blocks Challenges and approaches to attend to responsible AI in practice Tools to develop a strategic roadmap and techniques to foster an innovative team environment Multiple use cases that stem from the authors’ MIT classes, as well as from AI practitioners, AI project managers, early-career AI team leaders, technical executives, and entrepreneurs Exercises and Jupyter notebook examples
Download or read book Measurements Based Radar Signature Modeling written by Joseph T. Mayhan and published by MIT Press. This book was released on 2024-05-14 with total page 513 pages. Available in PDF, EPUB and Kindle. Book excerpt: A high-level text that synthesizes diverse research areas for characterizing objects (targets) from radar data and establishes a novel analysis framework for a class of signal processing techniques useful for high-resolution radar signature modeling. The only text to integrate a diverse body of work on characterizing objects (targets) from radar data into a common analysis framework, this book brings together the results of research papers and technical reports providing improved resolution and precision in radar target signature modeling and target motion solutions. It offers comprehensive coverage related to basic radar concepts, signal representation, and radar measurements; the development of advanced analysis tools essential for high-resolution signature modeling; the development of novel wideband and narrowband radar imaging techniques; the application of 2D spectral estimation theory to wideband signal processing; ultra-wideband scattering phenomenology and sparse-band sensor data fusion; and the integration of field measurements into the radar signature modeling process. The analysis techniques developed in the text provide the framework for a novel approach, called measurements-based modeling (MBM), to model target signatures by incorporating measurement data into the signature model of the target. Extensive examples throughout compare the performance of the new techniques with that of conventional analysis techniques. The first systematic, comprehensive synthesis of wide-ranging research areas for characterizing targets from radar data A deeply researched, lucid presentation enriched by extensive illustrations and examples An essential reference for experts in radar and signal processing, professional engineers in related fields, and graduate students
Download or read book A Wide Aperture HF Direction Finder written by Raymond F. Gleason and published by . This book was released on 1957 with total page 89 pages. Available in PDF, EPUB and Kindle. Book excerpt: The requirement has arisen for the development of facilities in the high-frequency region which will permit simultaneous message interception and instantaneous direction finding with a common antenna array. Preliminary study indicates that the most promising technique to meet these requirements would be a circularly disposed antenna array such as a Wullenweber system having a wide aperture, provided such a system could be designed and constructed with reasonable economy. The use of a wide aperture system should considerably reduce electrical interference and both site and wave interference errors. Preliminary studies of the system have been made using a circular array of vertical half-rhombic antennas. The resulting beam of the phased array exhibited variations in indicated bearings attributed to polarization changes and reduced its effectiveness in direction finding. Future studies and plans are outlined for an array using sleeve monopoles. (Author).
Download or read book Radio Direction Finding on High Frequency Short Duration Signals written by Dennis Dean Sheppard and published by . This book was released on 1980 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The feasibility of accomplishing high frequency direction finding against short duration (100-1000 ms) HF skywave signals using narrow aperture antennas is investigated. Two statistical procedures for estimating the signal bearing are proposed and compared. These procedures employ time averaging to reduce the large instantaneous bearing error caused by the phase and amplitude distortion of the wavefront due to scattering and multipath interference. Results are presented using data collected with the Southwest Research Institute Coaxial Spaced Loop HFDF system. It is shown that for a limited sample of data from this system the standard deviation of the bearing estimate for a 200 ms signal varied from 15 to 59 degrees. (Author).
Download or read book Small aperture Radio Direction finding written by Herndon H. Jenkins and published by Artech House Radar Library (Ha. This book was released on 1991 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Operating principles - Performance difinition - Direction-finding error sources - System level descriptions - Representative operational small-aperture - Passive geolocation - Subsystem considerations - Calibration and test of direction-finding systems.
Download or read book A Simulation Study of HF Direction Finding in the Presence of F region Scattering and Sporadic E written by and published by . This book was released on 1994 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents simulation studies modelling the operation of a sampled-aperture HF direction-finding (DF) system operating at high latitudes to obtain propagation models that are representative of high-latitude conditions, and to test various DF methods against those models to establish their utility. A model was developed for the scatter-supported ionosphere radio propagation, along with the sporadic-E propagation. The direction-finding operation is also modelled, including a two-dimensional array of antennas, and a direction-finding algorithm that obtains direction estimates from the signal samples received at the array elements. A plane-wave fitting algorithm that obtains a single direction corresponding to the best plane-wave fit to the received signal samples, and a MUSIC algorithm that is capable of obtaining a number of signal directions from a set of signal samples are modelled. DF system operation is simulated by running the model a number of times, with the scattering patch locations shifted a small amount each time, to simulate ionospheric drift motions. The resultant time histories of estimated bearing and elevation are examined to determine the appearance of the scattering and sporadic-E features, and the performance of the system. A particular set of simulations were used to study the time history of the observed signal directions from scattering, for various scattering-patch geometries and propagation parameters such as ionospheric electron density.
Download or read book Classical and Modern Direction of Arrival Estimation written by T. Engin Tuncer and published by Academic Press. This book was released on 2009-07-10 with total page 451 pages. Available in PDF, EPUB and Kindle. Book excerpt: Classical and Modern Direction of Arrival Estimation contains both theory and practice of direction finding by the leading researchers in the field. This unique blend of techniques used in commercial DF systems and state-of-the art super-resolution methods is a valuable source of information for both practicing engineers and researchers. Key topics covered are: - Classical methods of direction finding - Practical DF methods used in commercial systems - Calibration in antenna arrays - Array mapping, fast algorithms and wideband processing - Spatial time-frequency distributions for DOA estimation - DOA estimation in threshold region - Higher order statistics for DOA estimation - Localization in sensor networks and direct position estimation - Brings together in one book classical and modern DOA techniques, showing the connections between them - Contains contributions from the leading people in the field - Gives a concise and easy- to- read introduction to the classical techniques - Evaluates the strengths and weaknesses of key super-resolution techniques - Includes applications to sensor networks
Download or read book A Simulation Study of HF Direction Finding in the Presence of F region Scattering and Sporadic E written by Communications Research Centre (Canada) and published by . This book was released on 1994 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents simulation studies modelling the operation of a sampled-aperture HF direction-finding (DF) system operating at high latitudes to obtain propagation models that are representative of high-latitude conditions, and to test various DF methods against those models to establish their utility. A model was developed for the scatter-supported ionosphere radio propagation, along with the sporadic-E propagation. The direction-finding operation is also modelled, including a two-dimensional array of antennas, and a direction-finding algorithm that obtains direction estimates from the signal samples received at the array elements. A plane-wave fitting algorithm that obtains a single direction corresponding to the best plane-wave fit to the received signal samples, and a MUSIC algorithm that is capable of obtaining a number of signal directions from a set of signal samples are modelled. DF system operation is simulated by running the model a number of times, with the scattering patch locations shifted a small amount each time, to simulate ionospheric drift motions. The resultant time histories of estimated bearing and elevation are examined to determine the appearance of the scattering and sporadic-E features, and the performance of the system. A particular set of simulations were used to study the time history of the observed signal directions from scattering, for various scattering-patch geometries and propagation parameters such as ionospheric electron density.
Download or read book A Comparison of Spread and Point Source Multiple Direction Estimation Techniques for High Latitude HF Direction Finding written by Robert W. Jenkins and published by . This book was released on 1998 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previous simulation studies were conducted to determine the direction finding performance of four different antenna array geometries with and without antenna pattern errors, operating with the deterministic maximum likelihood (ML) algorithm. Here they are extended to a new DF algorithm, spread maximum likelihood (SML), which assumes distributions of signal directions, rather than single directions, to approximate the signal information seen by the array. The SML algorithm is thought to be more appropriate to the high latitude HF radio environment, where signals often arrive from a spread set of directions, due to multiple reflections or scattering from irregularities in the ionosphere and, at the same time, from a single great circle direction as a results of sporadic E propagation. Using a performance criterion of point source visibility in the presence of a stronger spread source, the simulation shows the SML technique to yield substantially better performance than ML, for all arrays and levels of error, and array apertures of four wavelengths or more. SML technique extended the useful range of array apertures upwards to 10 wavelengths in most cases. As was seen previously for the ML algorithm, the three pronged star configuration was found to be best of the array geometries tested.
Download or read book HF Direction Finding by Wavefront Testing written by D. W. Rice and published by . This book was released on 1980 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: Calculations are reported of the probability of observation of various degrees of phase-front non-linearity, for two and three signals incident from different directions upon a phase-measuring array. It is assumed that the signals fade independently, and that their amplitude probability densities are described by a Rayleigh law. It is shown that, under the worst-case conditions of equal powers in the signals, the probability of observing an rms phase deviation of 25 degrees or less from the best-fit straight line to the phase along an array, is about 0.5 when 2 rays are present, and about 0.2 when 3 rays are present. Experimental measurements over a 911-km mid-latitude path and a 2100-km trans-auroral-zone path, confirm the general behaviour predicted by the theory. It is well known that amplitude fading can be attributed to various ionospheric effects; however the measurements show that modulation imposed on the signal at the transmitter can also play an important part in decorrelating the amplitudes of signals received (after different time delays) via different ionospheric modes. In the latter case, the modulation can markedly reduce both the waiting time between phase-linear events, and their duration. The experimental program included concurrent measurements over the same path using FMCW, CW and SSB signals from a co-operative transmitter.
Download or read book A Maximum Likelihood HF Direction Finding Estimator for High Latitude Distributed Signals written by and published by . This book was released on 1999 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report details the development & evaluation of a new direction finding estimator, the spread maximum likelihood algorithm, targeted for high latitude high-frequency propagation conditions. Of particular concern are patches of enhanced electron density & associated instabilities in the ionosphere which drift across the polar cap during darkness, causing scattering of the propagated signal over a range of azimuth & elevation directions (the signals are spatially spread). The new estimator incorporates a spatial spreading model allowing it to simultaneously deal with both patch scattered signals and signals propagated by more normal propagation mechanisms, as well as to distinguish between the two types. Evaluation of the new estimator using both simulation & collected data is presented to compare its performance to both conventional & modern super-resolution approaches for high latitude propagation conditions.
Download or read book A Maximum Likelihood HF Direction Finding Estimator for High Latitude Distributed Signals written by William J. Read and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report details the development & evaluation of a new direction finding estimator, the spread maximum likelihood algorithm, targeted for high latitude high-frequency propagation conditions. Of particular concern are patches of enhanced electron density & associated instabilities in the ionosphere which drift across the polar cap during darkness, causing scattering of the propagated signal over a range of azimuth & elevation directions (the signals are spatially spread). The new estimator incorporates a spatial spreading model allowing it to simultaneously deal with both patch scattered signals and signals propagated by more normal propagation mechanisms, as well as to distinguish between the two types. Evaluation of the new estimator using both simulation & collected data is presented to compare its performance to both conventional & modern super-resolution approaches for high latitude propagation conditions.
