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Sensor synchronization, geolocation and wireless communication in a shipboard opportunistic arrayLoke, Yong 03 1900 (has links)
A wirelessly networked opportunistic digital array radar (WNODAR) is an integrated ship wide digital phased array, where the array elements are placed at available open areas over the entire surface of the platform. The array elements are self-standing digital transmit/receive (T/R) modules with no hardwire connections other than prime power. All control and digitized signals are passed wirelessly between the elements and a central signal processor. This research investigates the problem of integrating the array elements through the design of a wireless synchronization and geolocation network. Phase synchronization of array elements is possible using a simple synchronization circuit. A technical survey of geolocation techniques was performed, and performance curves for the WNODAR operating under different seastate conditions were obtained. Analysis and simulation results suggest that a position location scheme to correct for dynamic effects of hull deflection is not absolutely necessary for an array operating at a VHF or lower UHF frequency. Finally, a design of the demonstration T/R module is proposed. Based on projected communication requirements, the full-scale WNODAR demands a 3.7 Gb/s data transmission rate. The multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) approach has been identified as a promising solution to achieve gigabit transmission rates.
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Mapping of magnetospheric electric fields from Cluster into ionospheric convection from SuperDARN using the Tsyganenko field model.Maphaha, Fulufhelo Kenneth. January 2010 (has links)
The data from Super Dual Auroral Radar Network (SuperDARN) radar and Cluster was
used to investigate whether the processes observed by SuperDARN radar in the highlatitude
ionosphere leads to the processes that take place in the magnetosphere. SuperDARN
is a global network of high-frequency coherent-scatter radars operating in the
northern and southern hemispheres and these radars are capable of observing backscatter
from ionospheric irregularities. The Tsyganenko T96 field model was used to map the
footprint of the Cluster spacecraft into the ionosphere. The SuperDARN radar data analysis
software was used to generate time series, fi eld of view and convection plots. The
data from Syowa South, Syowa East SuperDARN radars, Advance Composition Explorer
(ACE) and Cluster spacecrafts was used in this study. Two events were found and
discussed, an event on 09 August 2002 and another event on 30 September 2002. The
SuperDARN radar and Cluster data for these events were compared. When a change in
electric field was observed by Cluster, SuperDARN radar observed a change in the convection
flow. There was a time delay between the change in the electric fi eld and the change
in convection flow. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.
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Study on 2002 sudden stratospheric warming, mesopher-lower thermospheric wind structure and dynamics and middle atmospheric structure, based on superDARN HF RADAR, LIDAR, Riometer, satellites and models.Mbatha, Nkanyiso Bongumusa. January 2012 (has links)
In this thesis, the dynamics and coupling in the middle atmosphere over the Southern
Hemisphere are investigated using SuperDARN high frequency (HF) radar wind data,
satellites, light detection and ranging (LIDAR), the South African National Antarctic
Expedition (SANAE) imaging riometer and models. In particular, the study focuses on
the unprecedented 2002 major stratospheric warming and its role in coupling the middle
atmosphere. The dynamics of the middle atmosphere is investigated in terms of mean
wind, temperature, gravity waves and planetary wave activity.
Studying the middle atmospheric thermal structure over Southern Africa is an important
activity to improve the understanding of atmospheric dynamics of this region. Observation
of a middle atmosphere thermal structure over Durban (29.9 S, 31.0 E, South Africa)
using LIDAR data collected from April 1999 to July 2004 (277 nights), including closest
overpasses of the Sounding of the Atmosphere using Broadband Emission Radiometry
(SABER) and Halogen Occultation Experiments (HALOE) satellites, and the COSPAR
International Reference Atmosphere (CIRA-86) are presented in this thesis. The observations
from the LIDAR instrument, satellites and CIRA-86 exhibit the presence of annual
oscillation in the stratosphere, whereas in the mesosphere the semi-annual oscillation seems
to dominate the annual oscillation at some levels. The stratopause is observed in the height
range of 40-55 km for all the instruments, with the stratopause temperatures being 260-
270 K for the LIDAR, 250-260 K for the SABER, and 250-270 K for the HALOE. Data
from the LIDAR, satellites and CIRA-86 model indicate almost the same thermal structure
of the middle atmosphere over Durban. This indicates a good agreement between
LIDAR, satellites and the CIRA-86 model.
Mean wind and planetary waves are investigated on a climatological scale in this study.
Mean wind observations from the SANAE SuperDARN HF radar are compared with
observations from Halley SuperDARN HF radar. There is a good agreement between the
observations from the two stations both in the zonal and meridional wind components.
Zonal wind is observed to be consistently larger than the meridional wind. The zonal
wind is also consistently more eastward at both stations with maxima occurring during
the solstice months. High latitude summer zonal mean
ow at 94 km is observed to
be weaker and more variable compared to the eastward winter mean circulation owing to
tropospherically forced planetary waves propagating through the middle atmosphere. The
zonal mean wind shows greater seasonal variability than does the meridional mean wind.
This seasonal behaviour is reasonably well understood in terms of the upward propagating
planetary waves and gravity waves interacting with the mean
ow. The Coriolis force also
plays an important role in the case of meridional wind component.
The climatology of planetary waves both in the zonal and meridional wind components indicates
an ampli cation of planetary waves of shorter wavenumbers (s = 3) in the winter
months. During summer, long period oscillations (e.g. >10 days) which are dominant in
winter disappear, and oscillations with shorter period (e.g. <10 days) become dominant.
vi
There is a strong planetary wave coupling between the stratosphere and mesosphere-lower
thermospheric (MLT) during the year 2002 winter season, whilst the coupling is observed
to be relatively weak during the other years. The strong planetary wave coupling in 2002
is understandable because during this year the middle atmosphere winter months were
characterised by strong planetary wave activity which led to the rst ever detection of the
SSW in the Southern Hemisphere.
In the year 2002 winter period the mean circulation in the stratosphere is characterized
by a series of planetary wave events that weakened the polar vortex and triggered the
sudden stratospheric warming in late September. In particular, in the stratosphere there
is a presence of a quasi 10-day eastward propagating planetary wave of wavenumber s=1,
while in the MLT a quasi 14-day eastward propagating planetary wave of wavenumber
s=1 is observed to be dominant. The Eliassen Palm
ux (E-P)
ux shows that strong
planetary wave activity observed in the middle atmosphere originates from the troposphere.
Zonal winds at the MLT show reversal approximately 7 days before the reversal at
stratosphere, indicating a downwards propagation of circulation disturbance in the middle
atmosphere. Eastward zonal winds dominate the winter MLT, but during the 2002 winter
there are many periods of westward winds observed compared to the other years. The
SABER vertical temperature pro les indicate cooling of the MLT region during the SSW
occurrence. Gravity wave horizontal phase velocities and horizontal wavelengths as seen
by the SANAE imaging riometer are observed to reduce dramatically over SANAE during
the occurrence of the stratospheric warming. The disturbance of the middle atmosphere
during the Southern Hemisphere stratospheric warming in year 2002 winter preconditioned
the region for gravity waves to propagate upward to the MLT. The potential energy of
these gravity waves is observed to increase with height up until they reach the lower thermosphere.
At the MLT they lose their energy, thus depositing their momentum, leading
to the MLT cooling and mean wind reversal.
Keywords: SSW, Planetary waves, Gravity waves, Stratosphere, MLT, SuperDARN radar,
Mean wind, Temperature, Middle atmosphere, SANAE. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2012.
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Design, implementation, and testing of a software interface between the AN/SPS-65(V)1 radar and the SRC-6E reconfigurable computer /Guthrie, Thomas G. January 2005 (has links) (PDF)
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Douglas J. Fouts. Includes bibliographical references (p. 61). Also available online.
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Projeto, desenvolvimento e construção de um modulador de pulso estado-solido para transmissores pulsados de alta potencia / Design, development and implementation of a solid-state pulse modulator for high-power pulse transmittersRondani, Bruno 12 February 2005 (has links)
Orientador: Jose Antenor Pomilio / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-06T14:09:31Z (GMT). No. of bitstreams: 1
Rondani_Bruno_M.pdf: 5870538 bytes, checksum: 69f2b2bd154400cd5b620b87a2c4fe8c (MD5)
Previous issue date: 2005 / Resumo: Descreve-se neste trabalho o desenvolvimento de uma topologia de modulador de pulso estado-sólido e a linha de retardo modular, para aplicação em transmissores pulsados de alta potência que utilizem válvulas de microondas magnetron empregadas comumente em radares de trajetografia, meteorologia e controle de tráfego aéreo. A pesquisa abrange o projeto, desenvolvimento e construção de um modulador de pulso destinado à modernização do transmissor do radar de trajetografia Bearn do Centro de Lançamentos de Foguetes da Barreira do Inferno, Natal -RN. O equipamento desenvolvido fornece pulsos de até 37,5kV e 60A em três modos de transmissão, a saber: monopulso longo, monopulso curto e bipulso. No modo monopulso longo, a largura de pulso é de 1,7µs e nos outros dois modos, 0,85µs. A taxa de repetição dos pulsos é de 585,5Hz. A unidade de modulação de pulso consiste de oito módulos de chaveamento em paralelo, conectados ao primário de um transformador de pulso de razão 1:50. Cada módulo contém dois trechos de linha de retardo e duas chaves estado-sólido e é capaz de gerar pulsos de até 790V e 390A nos diferentes modos de operação. A alimentação da linha de retardo é feita através de um circuito de carga composto por um indutor de alimentação e um circuito de Clipper. O indutor de alimentação faz com que a tensão de carga na linha seja dobrada em relação à tensão contínua presente na saída da fonte de alimentação de entrada, devido à ressonância série criada entre esse indutor e a capacitância total das linhas de retardo. O circuito de Clipper garante a regulação de tensão pulso a pulso e a proteção do modulador contra surto de sobre-corrente na carga e sobre-tensão nas linhas de retardo. Esta topologia foi desenvolvida para melhorar a confiabilidade e facilitar a manutenção dos transmissores de radar com a implementação do conceito de degradação suave (graceful degradation) do modulador de pulso / Abstract: This work describes the development of a modular line-type solid-state pulse modulator topology to be applied in magnetron pulsed power radar transmitters, commonly found on tracking, weather and air traffic management radars. This research includes the design, development and assembling of a pulsed modulator for the Barreira do Inferno Launching Center (CLBI, Natal-RN) Bearn tracking radar upgrade program. The equipment developed provides pulses of 37.5 KV and 60 A in three transmission modes: single long pulse, single short pulse and bipulse. In the single long pulse the pulse width is 1.7 µs and in the other modes 0.85 µs. The pulse repetition frequency is of 585.5Hz. The modulator unit is composed by eight switching modules connected in parallel with the primary windings of a 1:50 ratio pulse transformer. Each module has two pulse-forming network and two IGBT switches and it is capable of handling 790 V and 390 A in the three operational modes. An inductor and a Clipper circuit implement the pulse-forming network charging. The charging inductor allows charging the pulse-forming network with twice the supply voltage since there is a resonance with the total modulator capacitance. The Clipper circuit assures the pulse-to-pulse charging voltage regulation and protects the modulator against load over-current and over-voltage charging. This topology was developed to improve reliability and maintainability of radar transmitters by implementing the graceful degradation (soft failure mode) in the pulse modulator / Mestrado / Sistemas e Controle de Energia / Mestre em Engenharia Elétrica
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Design, implementation, and testing of a software interface between the AN/SPS-65(V)1 radar and the SRC-6E reconfigurable computerGuthrie, Thomas G. 03 1900 (has links)
Approved for public release, distribution is unlimited / This thesis outlines the development, programming, and testing a logical interface between a radar system, the AN/SPS-65(V)1, and a general-purpose reconfigurable computing platform, the SRC Computer, Inc. model, the SRC-6E. To confirm the proper operation of the interface and associated subcomponents, software was developed to perform basic radar signal processing. The interface, as proven by the signal processing results, accurately reflects radar imagery generated by the radar system when compared to maps of the surrounding area. The research accomplished here will allow follow on research to evaluate the potential benefits reconfigurable computing platforms offer for radar signal processing. / Captain, United States Marine Corps
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