Ретроспективный обзор троичных последовательностей с идеальной периодической автокорреляцией и устройств их генерации

Introduction. Perfect polyphase unimodular sequences, i.e. sequences with ideal periodic autocorrelation and single amplitude of symbols are widely used in modern radio communications and radars. Among them a special place is occupied by perfect ternary sequences (PTSs) with elements {–1, 0, 1}. PTSs are quite numerous and their length in comparison with perfect binary sequences is not limited from above. There is a well-known review of PTS families undertaken by Fan and Darnell in 1996. However, over the past two decades numerous new PTS families have been discovered. Connections between PTSs and circulant weighing matrices have been established and certain theorems on the existence of PTS existence for certain lengths have also been obtained. Therefore, there is a need for a new modern review of existing PTSs.Objective. This review of existing PTSs is intended for developers of radio electronic systems using perfect sequences. Materials and methods. Domestic and foreign sources of information (books, journal papers, conference proceedings, patents) were considered and analysed. A Web search was carried out based on keywords using resources of Yandex and Google, as well as in digital electronic libraries (Russian State Library (RSL), IEEE Xplore Digital Library), conference materials (Digital Signal Processing and its Application (DSPA), Sequences and their Applications (SETA), etc.). Results. In addition to the matter of collating an informational bibliography, the review shows the relationship between PTSs obtained at different times and their connection with circulant weighing matrices. The review also describes the generators of known PTS families (Ipatov, Hoholdt-Justensen, etc.). Conclusion. A retrospective review of PTSs is herein presented and the generators of certain known PTS families have been considered. The results of the study are relevant for use in modern radio communications and radar systems and in CW and LPI radars in particular. Введение. Идеальные многофазные унимодулярные последовательности, т. е. последовательности с идеальной периодической автокорреляцией и единичной амплитудой символов, широко используются в современной радиосвязи и радиолокации. Особое место среди них занимают идеальные троичные последовательности (ИТП) с элементами {–1, 0, 1}. ИТП достаточно многочисленны, а их длина в отличие от идеальных двоичных последовательностей не ограничена сверху. Известен обзор ИТП, сделанный Фаном и Дарнеллом в 1996 г. Однако за прошедшие два десятилетия были открыты новые многочисленные семейства ИТП, установлены связи между ИТП и циркулянтными взвешенными матрицами, получены теоремы о существовании ИТП с определенными параметрами. Поэтому возникла потребность в новом современном обзоре известных на сегодня ИТП. Цель работы. Обзор современных ИТП предназначен для разработчиков радиоэлектронных систем, в которых используются идеальные последовательности.Материалы и методы. Рассмотрены и проанализированы отечественные и зарубежные источники информации (книги, журнальные статьи, труды конференций, патенты). Поиск осуществлялся в сети Интернете по ключевым словам с использованием Интернет-ресурсов Yandex и Google, а также в цифровых электронных библиотеках (Российской Государственной библиотеке (РГБ), IEEE Xplore Digital Library), в материалах конференций (Цифровая Обработка Сигналов и ее Применение (DSPA), Sequences and Their Applica-tions (SETA), и др.). Результаты. Наряду с решением информационно-библиографической задачи в обзоре показана взаимосвязь полученных в разное время ИТП, их эквивалентность циркулянтным взвешенным матрицам, а также рассмотрены устройства генерации известных семейств ИТП (Ипатова, Хохолдта-Джастесена и др.). Заключение. Представлен ретроспективный обзор ИТП; рассмотрены генераторы известных семейств ИТП. Результаты исследования актуальны для применения в современных системах радиосвязи и радиолокации, в частности в CW- и LPI-радарах.

Nonlinear Suppression of Range Ambiguity in Pulse Doppler Radar

Coherent pulse train processing is most commonly used in airborne pulse Doppler radar, achieving adequate transmitter/receiver isolation and excellent resolution properties while inherently inducing ambiguities in Doppler and range. First introduced by Palermo in 1962 using two conjugate LFM pulses, the primary nonlinear suppression objective involves reducing range ambiguity, given the waveform is nominally unambiguous in Doppler, by using interpulse and intrapulse coding (pulse compression) to discriminate received ambiguous pulse responses. By introducing a nonlinear operation on compressed (undesired) pulse responses within individual channels, ambiguous energy levels are reduced in channel outputs. This research expands the NLS concept using discrete coding and processing. A general theory is developed showing how NLS accomplishes ambiguity surface volume removal without requiring orthogonal coding. Useful NLS code sets are generated using combinatorial, simulated annealing optimization techniques - a general algorithm is developed to extended family size, code length, and number of phases (polyphase coding). An adaptive reserved code thresholding scheme is introduced to efficiently and effectively track the matched filter response of a target field over a wide dynamic range, such as normally experienced in airborne radar systems. An evaluation model for characterizing NLS clutter suppression performance is developed - NLS performance is characterized using measured clutter data with analysis indicating the proposed technique performs relatively well even when large clutter cells exist

Adaptive Coding, Modulation and Filtering of Radar Signals

In this chapter, some of the issues associated with radar signal processing are highlighted, with an emphasis on adaptability. Signal processing operations are carried by systems in order to enhance the received signal or to clarify its content of information. Received radar signal should be subjected to processing prior to the extraction of useful target information out of it so as to emphasize desired signal among other accompanying signals. Processing of the radio frequency (RF) signal is generally done in an analogue manner, while digital signal processing (DSP) became dominant in the intermediate-frequency (IF) and low-frequency portions of the system. Since the detectability and immunity against interference and clutter strongly depend on the waveform used, it will be more efficient to apply a diverse waveform instead of confinement to an invariable waveform of a fixed code and pattern. Adaptive coding, modulation and filtering of radar signals provide high degree of diversity as well as flexibility and agility for signal processors versus changing sources of interference and environmentally dependent reflectors. Constant false alarm rate (CFAR) is an adaptive processing technique that reduces noise and clutter. Different methods are applied in CFAR technique to adaptively cope with varying clutter density and distribution

Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z

Papers from the conference are presented, and the topics covered include the following: planetary geology, meteorites, planetary composition, meteoritic composition, planetary craters, lunar craters, meteorite craters, petrology, petrography, volcanology, planetary crusts, geochronology, geomorphism, mineralogy, lithology, planetary atmospheres, impact melts, K-T Boundary Layer, volcanoes, planetary evolution, tectonics, planetary mapping, asteroids, comets, lunar soil, lunar rocks, lunar geology, metamorphism, chemical composition, meteorite craters, planetary mantles, and space exploration

Ninth annual V.M. Goldschmidt Conference : August 22-27, 1999, Harvard University, Cambridge, Massachusetts

The meeting is a forum for presenting and discussing new chemical and isotopic measurements, experimental and theoretical results, and discoveries in geochemistry and cosmochemistry.sponsored by Geochemical Society ... [and others]hosted by Department of Earth and Planetary Sciences, Harvard University ; compiled by Lunar and Planetary Institute.PARTIAL CONTENTS: Bacteria-promoted Dissolution of a Common Soil Silicate / S.L. Brantley, L.I. Liermann, and B.E. Kalinowski--Evolution of Temperature Control on Alkenone Biosynthesis / S.C. Brassell--Chemical Composition of Silurian Seawater: Preliminary Results from Environmental Scanning Electron Microscopy-Energy Dispersive Spectroscopy Analyses of Fluid Inclusions in Marine Halites / S.T. Brennan, T. Lowenstein, M.N. Timofeeff, and L.A. Hardi

The Twenty-Fifth Lunar and Planetary Science Conference. Part 3: P-Z

Various papers on lunar and planetary science are presented, covering such topics as: impact craters, tektites, lunar geology, lava flow, geodynamics, chondrites, planetary geology, planetary surfaces, volcanology, tectonics, topography, regolith, metamorphic rock, geomorphology, lunar soil, geochemistry, petrology, cometary collisions, geochronology, weathering, and meteoritic composition

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

The Second Conference on Lunar Bases and Space Activities of the 21st Century, volume 2

These 92 papers comprise a peer-reviewed selection of presentations by authors from NASA, the Lunar and Planetary Institute (LPI), industry, and academia at the Second Conference on Lunar Bases and Space Activities of the 21st Century. These papers go into more technical depth than did those published from the first NASA-sponsored symposium on the topic, held in 1984. Session topics included the following: (1) design and operation of transportation systems to, in orbit around, and on the Moon; (2) lunar base site selection; (3) design, architecture, construction, and operation of lunar bases and human habitats; (4) lunar-based scientific research and experimentation in astronomy, exobiology, and lunar geology; (5) recovery and use of lunar resources; (6) environmental and human factors of and life support technology for human presence on the Moon; and (7) program management of human exploration of the Moon and space

UMSL Bulletin 2004-2005

https://irl.umsl.edu/bulletin/1010/thumbnail.jp