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The next generation of receivers for applications such as radio astronomy, spectrum surveillance, and frequency-adaptive cognitive radio will require the capability to digitize very large bandwidths in the VHF low band (30 to 100 MHz). However, methodology for designing such a receiver is not well established. The difficulties of this design are numerous. There are various man-made interferers occupying this spectrum which can block desired signals or spectrum, either directly or through intermodulation. The receivers will typically use simple (i.e., narrowband) antennas, so the efficiency of power transfer to the preamplifier needs to be carefully considered. This thesis takes these design challenges into account and produces a seven step design methodology for direct sampling wideband digitizing receivers. The methodology is then demonstrated by example for three representative receivers. Finally, improvements to the analysis are suggested. / Master of Science

With the increasing demand for access to the crowded radio frequency spectrum, cognitive radios have been suggested as one solution. Cognitive radios would be frequency agile and able to sense their radio environment and opportunistically use empty spectrum. Spectrum sensing, monitoring a given band of spectrum to see if it is occupied, is an essential part of a cognitive radio. The preferred method of spectrum sensing is the energy detector, which does not require any a priori information about the signal to be detected and is computationally simple to implement. Man-made noise, impulsive in nature, has also become more prevalent with the widespread use of electronic devices. In this thesis, we took measurements of man-made impulsive noise in the broadcast digital television bands to measure its presence, power, and spatial correlation. The effects of impulsive noise on the detection performance of an energy detector were analyzed. Lastly, a wideband RF receiver was designed, built, and tested on the Virginia Tech campus, which would be well suited both to spectrum sensing and taking measurements of impulsive noise. / Master of Science

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / The VHF air/ground data link of CAAC is introduced in detail. This paper proposes a solution of VHF air/ground data link system, which exchanges downlink messages and uplink messages in data link information processing networks. The following topics are covered in this paper: components of VHF data link; data processing and design about VHF data link Gateway system; the application of VHF air/ground data link in airlines.

Intervjuer med kunniga på AIS-området har utförts parallellt med en enkät riktad till aktiva befäl ute till sjöss. Detta i syfte att ta reda på dels hur detta hjälpmedel bör användas vad avser antikollision, dels hur det faktiskt används i praktiken. AIS, Automatic Identification System, är ett informationsdelningssystem som hjälper fartyg att navigera säkert genom att sända ut egen navigationsdata och samtidigt ta emot motsvarande information från andra fartyg. Systemet nyttjas även som informationssystem för landbaserade stationer såsom VTS-centraler och kustbevakning. Undersökningen har engagerat och visat att expertisen anser att AIS, i många avseenden, är ett bra och användbart hjälpmedel som bör komplettera övrig utrustning vid bedömning om kollisionsrisk. Vidare visar enkäten att ARPA-systemet, trots vissa inneboende brister, tillmäts större förtroende än AIS och AIS-vektorer används därför sparsamt. Enkäten visar även att en stor del av de aktiva inte är främmande för att göra avsteg från sjövägsreglerna emedan expertisen i huvudsak avråder från sådant. / Interviews with experts, in the field of AIS, have been conducted alongside a quantitative survey aimed at certified seagoing officers. The purpose of the survey was to investigate how this navigational aid preferably should be used in collision avoidance, in contrast to how it is used in reality. AIS, Automatic Identification System, is an information sharing system to assist in safe navigation by transmitting the own vessels navigational data while, at the same time, receiving corresponding information from other ships. The system is also utilized by land based stations such as VTS-centers and coast guards. The investigation shows that experts conclude AIS to be, in many aspects, a good and useful aid which should be used in collaboration with other equipment when assessing risk of collision. Furthermore, the survey show that the ARPA-system, in spite of some internal shortcomings, is awarded more trust than AIS and AIS vectors are therefore rarely used. The survey also shows that a large number of officers are open to deviating from the COLREGs while the experts, in general, advise against it.

In the pre-lacation, lactation and post-lactation periods in 2010 and 2011 and the pre-lactation period in 2012 we used radio-telemetry to determine changes in home range and habitat activity and preference of the maternity colony of the Mediterranean horseshoe bat (Rhinolophus euryale) in Slovak Karst. The colony roosted in the attic of the monastery in Jasov. This area represents the northern margin of the species distribution range. In total, we tagged 35 females that were radio-tracked for 31 nights. For the all pre- lactation periods 17 females were marked, in the lactation periods 12 females were marked, and 6 females were marked in the post-lactation periods. The females were marked with radiotags and the VHF telemetry (radio telemetry using very high frequencies) was used. We compared the spatial and habitat preferences in the above defined seasons of the annual reproductive cycle. The total number of recorded locations was 858 for all reported periods. We compared the varios aspects of activity of the females during the night in the particular periods. We have shown that the females left their roost in the pre-lactation periods as the most late. These were followed by the females in the lactation periods and as the most early after the sunsetthe roost was left by the females in the...

<p>Intervjuer med kunniga på AIS-området har utförts parallellt med en enkät riktad till aktiva befäl ute till sjöss. Detta i syfte att ta reda på dels hur detta hjälpmedel bör användas vad avser antikollision, dels hur det faktiskt används i praktiken.</p><p>AIS, Automatic Identification System, är ett informationsdelningssystem som hjälper fartyg att navigera säkert genom att sända ut egen navigationsdata och samtidigt ta emot motsvarande information från andra fartyg. Systemet nyttjas även som informationssystem för landbaserade stationer såsom VTS-centraler och kustbevakning.</p><p>Undersökningen har engagerat och visat att expertisen anser att AIS, i många avseenden, är ett bra och användbart hjälpmedel som <em>bör</em> komplettera övrig utrustning vid bedömning om kollisionsrisk. Vidare visar enkäten att ARPA-systemet, trots vissa inneboende brister, tillmäts större förtroende än AIS och AIS-vektorer används därför sparsamt. Enkäten visar även att en stor del av de aktiva inte är främmande för att göra avsteg från sjövägsreglerna emedan expertisen i huvudsak avråder från sådant.</p> / <p>Interviews with experts, in the field of AIS, have been conducted alongside a quantitative survey aimed at certified seagoing officers. The purpose of the survey was to investigate how this navigational aid preferably should be used in collision avoidance, in contrast to how it is used in reality.</p><p>AIS, Automatic Identification System, is an information sharing system to assist in safe navigation by transmitting the own vessels navigational data while, at the same time, receiving corresponding information from other ships. The system is also utilized by land based stations such as VTS-centers and coast guards.</p><p>The investigation shows that experts conclude AIS to be, in many aspects, a good and useful aid which <em>should</em> be used in collaboration with other equipment when assessing risk of collision. Furthermore, the survey show that the ARPA-system, in spite of some internal shortcomings, is awarded more trust than AIS and AIS vectors are therefore rarely used. The survey also shows that a large number of officers are open to deviating from the COLREGs while the experts, in general, advise against it.</p>

Le développement de l’électronique embarquée et miniaturisée est pleinement d’actualité de nos jours, dans les domaines tels que l’armement, la médecine, et les télécommunications. La miniaturisation des antennes large-bande, opérationnelles sur plus d’une décade, présentent un défi particulier. Ces travaux de thèse proposent de travailler sur la miniaturisation d’une antenne spirale, afin d’en réduire l’encombrement, à savoir son diamètre, tout en conservant au mieux ses caractéristiques de rayonnement et polarisation intrinsèques. Cette recherche sera appliquée à la bande des Très hautes Fréquence (Very High Frequencies – VHF), allant de 30MHz à 300MHz La géométrie inédite proposée consiste à associer à une antenne spirale un ensemble d’anneaux résonnants, dont le diamètre n’excède pas celui de la spirale, et permettant de diminuer la fréquence basse de fonctionnement. Pour un ensemble de cinq anneaux associé à la spirale, la réduction de la fréquence basse de fonctionnement est de plus de 30%. Pour deux antennes spirales de même fréquence basse de fonctionnement, l’antenne miniaturisée a donc un diamètre réduit de 30%, soit une surface réduite de 50%. Les performances de l’état de l’art d’après lesquelles les réductions sur le diamètre des antennes spirales n’excèdent pas 15% sont donc dépassées. De plus, d’après cet état de l’art, les méthodes de réduction appliquées aux antennes large bande dégradent en général le gain et l’axial ratio dans les bandes basses de fréquences de fonctionnement. La méthode proposée permet de conserver l’efficacité de l’antenne, voire de l’augmenter, dans les fréquences proches de la fréquence basse de fonctionnement. Le rayonnement de l’antenne spirale miniaturisée dans la bande passante de l’antenne sans anneaux n’est pour autant pas modifiée. Ces résultats très encourageant ont été confirmés par la mesure d’antennes spirales miniaturisées, réalisées pour un diamètre de 8cm et de 1m : une réduction de 30% du diamètre sans dégradation du rayonnement a été observée. Les mesures ont par ailleurs donné lieu à l’étude de la réalisation d’une antenne en bande VHF, avec pour implication les problématiques de réalisation (masse, encombrement, résistance mécanique) et de mesure (isolation, effets parasites en VHF avec une longueur d’onde de 4m). / Miniaturizing electronic devices is a great challenge in crucial research domain such as defense, medicine, and telecommunications. Wideband antenna miniaturization operating on more than a decade is a particular issue. This thesis presents an original method for miniaturizing a spiral antenna, reducing its diameter while keeping its bandwidth, its radiating performances and its axial ratio characteristics. This method is applied to UHF spiral antenna (from 750MHz) and VHF antenna (from 75MHz). The new geometry adds stacked resonant rings to an Archimedean spiral antenna. Their diameter are the same, hence no rise of the antenna diameter. For a 5-ring spiral antenna, the lowest operating frequency reduction is higher than 30%. That is equivalent to a 30% reduction of the diameter for two antennas sharing the same lowest operating frequency, hence a 50% reduction of the area of the antenna. These reduction factors surpass the reduction factors of the state of art of 15%. Besides, according to the state of art, the miniaturizing techniques imply some degradation of the gain and axial ratio performances at the lowest operating frequencies. The new method improves on the other hand these characteristics at these frequencies. At higher frequencies, the rings do not interfere with the matching of neither the spiral antenna nor its radiation characteristics. These results were validated by fabricated antenna measurements. A 30% reduction of the diameter was obtained on a 5-ring-8cm-large antenna as well as on a 5-ring-1m-large antenna. No impairment was noticed on the radiation of the antennas, even at the lowest operating frequencies. The thesis also discusses the difficulties which came in addition for the fabrication (mass, size and mechanical resistance) and measurement (radiation interferences and measurement isolation – the wavelength being 4m) of the VHF antenna.

[pt] O presente estudo tem por objetivo identificar e analisar, a partir do modelo proposto por Swales (1990), os movimentos retóricos existentes nas comunicações em VHF em inglês e os propósitos comunicativos subjacentes, em chamadas entre navios da Marinha Mercante. Ainda, procura discriminar nestas comunicações os elementos lexicais mais recorrentes no gênero com base no estudo de Halliday e Hasan (1976; 1994), mais especificamente sobre repetição. Estas comunicações descrevem cinco tipos de procedimentos básicos: Troca, Aviso, Perigo, Urgência e Segurança. O estudo qualitativo foi feito através da análise de 33 textos simulados de comunicações em VHF, retirados de livros técnicos de Inglês Marítimo e apostilas de exercícios, utilizados nos Cursos de Marinha Mercante. Foram realizadas, também, cinco entrevistas com oficiaisalunos de Náutica para confirmar a análise das variações identificadas nas simulações e para esclarecer as práticas comunicativas da comunidade mercante, face as variações percebidas nos textos. Ademais, a análise dos textos revela elementos obrigatórios e opcionais nas chamadas simuladas e sugere que as mudanças em suas estruturas são principalmente lexicais. Os resultados mostram que cada movimento possui um conjunto de funções próprias, realizado pelas escolhas léxico-gramaticais específicas. / [en] This research identifies and analyzes the rhetorical structure of VHF communication in English on Merchant Marine ships and the communicative purposes underlying this communication, using SWALES (1990) model originally created for the analysis of introductions in research papers. The research also analyses the lexical choices for the genre, based on Halliday e Hasan (1976; 1994). VHF communication includes five types of basic procedures: Exchange, Broadcast, Pan Pan, Mayday, and Sécurité. The qualitative study was conducted by means of the textual analysis of 33 simulations of VHF communication, all taken from course books and practice materials for Maritime English, used at the Merchant Marine course in Rio de Janeiro. Interviews were also conducted with five student- officers from the Nautical area, so as to confirm the analysis of the variations identified in the simulations and to clarify the communicative practices of the merchant community, in light of the variations observed in the texts. The textual analysis shows obligatory and optional elements in the rhetorical structure of the simulated communications and indicates that the variations in the structure are primarily lexical. The results also show that each movement possesses its own set of functions that are realized by lexical and grammatical choices.