Дисертації з теми "Ionospheic wave propagation"
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Tshisaphungo, Mpho. "Validation of high frequency propagation prediction models over Africa." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1015239.
Повний текст джерелаLöfås, Henrik. "Ionospheric modification by powerful HF-waves : Underdense F-region heating by X-Mode." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-121898.
Повний текст джерелаDe, Larquier Sebastien. "The mid-latitude ionosphere under quiet geomagnetic conditions: propagation analysis of SuperDARN radar observations from large ionospheric perturbations." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/24770.
Повний текст джерелаPh. D.
Negale, Michael. "Investigating the Climatology of Mesospheric and Thermospheric Gravity Waves at High Northern Latitudes." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/6937.
Повний текст джерелаOronsaye, Samuel Iyen Jeffrey. "Updating the ionospheric propagation factor, M(3000)F2, global model using the neural network technique and relevant geophysical input parameters." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001609.
Повний текст джерелаMercer, Christopher Crossley. "The search for an ionospheric model suitable for real-time applications in HF radio communications." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1005274.
Повний текст джерелаBotai, Ondego Joel. "Ionospheric total electron content variability and its influence in radio astronomy." Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1005258.
Повний текст джерелаCarozzi, Tobia. "Radio waves in the ionosphere : Propagation, generation and detection." Doctoral thesis, Uppsala universitet, Institutionen för astronomi och rymdfysik, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1184.
Повний текст джерелаCarozzi, Tobia D. "Radio waves in the ionosphere : propagation, generation, and detection /." Uppsala : Institutionen för astronomi och rymdfysik, Univ. [distributör], 2000. http://publications.uu.se/theses/99-3364278-2/.
Повний текст джерелаHabarulema, John Bosco. "A contribution to TEC modelling over Southern Africa using GPS data." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1005241.
Повний текст джерелаOpperman, B. D. L. "Reconstructing ionospheric TEC over South Africa using signals from a regional GPS network." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005273.
Повний текст джерелаStarks, Michael James 1971. "Measurement of the conjugate propagation of VLF waves by matched filter and application to ionospheric diagnosis." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80126.
Повний текст джерелаIncludes bibliographical references (p. 173-176).
by Michael James Starks.
Sc.D.
Nordblad, Erik. "Opening New Radio Windows and Bending Twisted Beams." Doctoral thesis, Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-158797.
Повний текст джерелаBergadà, Caramés Pau. "Oblique Sounding and HF Communication Techniques for Very Long Haul Ionospheric Links." Doctoral thesis, Universitat Ramon Llull, 2015. http://hdl.handle.net/10803/285837.
Повний текст джерелаLos sistemas de radio de alta frecuencia (HF, en inglés) son usados por agencias gubernamentales y no gubernamentales en todo el mundo siempre que se necesite una alternativa a las comunicaciones por satélite: barcos en alta mar, aviones fuera del rango de cobertura de las redes radio de visión directa, operaciones militares, zonas donde la infraestructura ha sido destruida por algún desastre. Ésta ofrece una alternativa, o representa un sistema de backup, a las comunicaciones vía satélite, evitando los costes, la vulnerabilidad y los problemas de soberanía de las comunicaciones por satélite. En esta tesis se ha estudiado el enlace HF entre la base antártica española Juan Carlos I en la isla Livingston, en las Shetland del sur y España. El objetivo de este trabajo es el estudio de las limitaciones de la propagación ionosférica (como la relación señal a ruido e interferencia, la dispersión multicamino y la dispersión por efecto Doppler) y el diseño de la capa física de un enlace HF de baja velocidad, baja potencia y largo alcance. Se han estudiado un par de propuestas para este enlace, como son el espectro ensanchado por secuencia directa (DSSS, en inglés) y la multiplexación por división en frecuencia ortogonal (OFDM, en inglés). El reto ha sido definir las características que mejor se adecuan a este enlace para poder aprovechar la diversidad temporal y frecuencial que ofrece el canal HF. Desde el año 2003 diversas campañas de sondeo han permitido estudiar el canal HF pero no es hasta la campaña 2009/2010 que se consigue una fotografía de la actividad ionosférica tanto nocturna como diurna. En los artículos que se presentan en esta tesis hemos extendido los estudios previos a todo el rango de frecuencias HF y hemos mostrado las diferencias entre el día y la noche. Hemos usado estos resultados de caracterización del canal para diseñar y comparar símbolos DSSS y símbolos OFDM. Ambas posibilidades han resultado ser posibles candidatas para implementar un enlace HF de baja velocidad entre la Antártida y España. Sin embargo ambas técnicas representan dos aproximaciones distintas a la implementación del módem. Mientras que DSSS consigue un buen funcionamiento a baja velocidad en escenarios con baja relación señal a ruido, OFDM consigue tasas de transmisión más altas en escenarios más benignos.
High Frequency (HF) radio is used by governmental and non nongovernmental agencies worldwide whenever an alternative to satellites for sky wave communication is needed: ships at sea, aircraft out of range of line-of-sight radio networks, military operations, disaster areas with communication infrastructure destroyed or distant regions lacking other communications. It offers an alternative to satellites, or a backup, for long-haul communications, thus avoiding the costs, vulnerabilities and sovereignty concerns of satellite communications. In this thesis the HF link between the Antarctic Spanish Station Juan Carlos I in Livingston Island, South Shetlands and Spain is studied. The aim of this study is to address the impairments that affect HF propagation (i.e., signal-to-noise plus interference ratio, multipath and Doppler shift and spread) and to design the physical layer of a low rate, low power and long-haul HF link. Some proposals regarding this last issue are addressed, i.e., direct sequence spread spectrum (DSSS) and orthogonal frequency division multiplexing (OFDM). The challenge is to define the symbol characteristics that best fit the link to benefit from time and frequency diversity that offers the HF channel. Since 2003 several transmission campaigns have allowed to study the HF channel but it is not until the 2009/2010 campaign that we have achieved a whole picture of both diurnal and nocturnal ionospheric activity. In the papers presented in this thesis we have extended the previous research to the whole range of HF frequencies and we have shown the differences on performance between day and night. We have used the results from channel characterization to design and compare the performance of DSSS and OFDM symbols. Both techniques have turned out to be possible candidates to implement a low rate HF link between Antarctica and Spain. However, both techniques stand for different approaches of the modem: DSSS achieves good performance at low data rate in low SNR scenarios, whereas OFDM achieves higher data rate in benign channels
Ayachi, Mohamed. "Determination de la temperature dans la mesosphere a partir de la mesure de la vitesse de phase des ondes longues sur un trajet grande distance." Caen, 1988. http://www.theses.fr/1988CAEN2021.
Повний текст джерелаHsiao, Chun-Chieh, and 蕭俊傑. "A study of vertical energy propagation of ionospheric wave." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/05550502382686655611.
Повний текст джерела國立中央大學
太空科學研究所
92
In this dissertation, a procedure deriving the vertical group and phase velocities of periodic waves in the ionosphere is proposed. The method is based on Fourier analysis and considered the difference of angular frequency and wave number as a function of number of data points used in a spectral analysis. Simulations and observations from ionosondes and a VHF radar are investigated to understand the vertical propagation and source of the waves. The simulation is employed to demonstrate the usefulness of the procedure while some noises are added and multiplied to the wave packet for examing the suitability and stability of the procedure. The developed procedure is further applied to analyze waves appearing in transient layers during a solar eclipse and appearance of an additional sub-layer as well as a permanent layer of the F-region. A study of the waves caused by repid change of sunlight during the solar eclipse shows that the energy source lies at the altitude near the F1 peak. An examination of the waves during appearance of the additional layer in the equatorial regions indicates the wave source is around the peak of the layer. An analysis of the data observed from ionosonde and the VHF radar, the F2 peak is an energy source of the associated waves. Results of this dissertation demostrate the waves sources are mainly around the peaks of layers in the ionosphere.
Bremner, Sherry. "Analysing transient effects in the ionosphere using narrowband VLF data." Thesis, 2009. http://hdl.handle.net/10413/8323.
Повний текст джерелаThesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.
Opperman, B. D. L. "Reconstructing ionospheric TEC over South Africa using signals from a regional GPS network /." 2007. http://eprints.ru.ac.za/1129/.
Повний текст джерела"Feasibility study of ionospheric tomography using HF radar." Thesis, 2010. http://hdl.handle.net/10413/1035.
Повний текст джерелаFriedel, Reiner Hans-Walter. "A study of wave induced electron precipitation at low and middle latitudes." Thesis, 1991. http://hdl.handle.net/10413/5682.
Повний текст джерелаThesis (Ph.D.)-University of Natal, Durban, 1991.
Sedeh, Leila Norouzi. "Doppler clutter in HF radar systems produced by ULF waves." Thesis, 2014. http://hdl.handle.net/1959.13/1042283.
Повний текст джерелаUltra low frequency (ULF) waves are generated by the interaction of the solar wind with Earth’s magnetosphere. The waves propagate through the ionosphere and may be seen in data from SuperDARN Over-The-Horizon radars as oscillations in Doppler velocity which coincide with oscillations of the geomagnetic field recorded by ground magnetometers. Data from the two Tasman International Geospace Environment Radars (TIGER) and the magnetometer located on Macquarie Island over 2006-2009 show that ULF wave signatures are common. The dependence with time of day showed most ULF radar events occurred between 6-12 UT (dusk and pre-mid-night sector). Using the Maximum Entropy Method (MEM) several spectral aspects of detected ULF waves were investigated for the first time. Most of the recorded frequencies were in the range 1- 4 mHz. Some frequencies were seen more often than others with the more common frequencies spaced about 0.3mHz apart, consistent with previous studies. There was no evidence of a frequency dependence on latitude. Field line resonance (FLR) signatures in the radar data were expected but were not common, as shown by comparisons with coincident ground magnetometer data. This study has shown that most radar echoes containing ULF wave Doppler signatures appear to be backscattered from the plasmapause region mapped into the ionosphere. Modelling of the Doppler velocity combined with a ULF wave model and two dimensional ray tracing was achieved for the first time. The results are consistent with experimental observations. With further improvement, this modelling should provide a valuable tool to understand shear Alfven mode and fast mode plasma wave interactions within the ionosphere and their effects on HF propagation through the ionosphere.
Wadley, T. L. "Heterodyne techniques in specialised radio instrumentation." Thesis, 2015. http://hdl.handle.net/10539/18064.
Повний текст джерелаVuthaluru, Rupa. "MF radar observations of D-region electron densities at Adelaide / by Rupa Vuthaluru." 2003. http://hdl.handle.net/2440/22029.
Повний текст джерелаIncludes bibliographical references (leaves 177-183)
xxii, 183 leaves : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, School of Chemistry and Physics, Discipline of Physics and Mathematical Physics, 2004
Massa, M. "Waveforms analysis to improve earthquake location procedures: theory and applications." Thesis, 2005. http://hdl.handle.net/2122/5898.
Повний текст джерелаIstituto Nazionale di Geofisica e Vulcanologia, sezione di Milano-Pavia
Unpublished
3.1. Fisica dei terremoti
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