Forecasting of the electromagnetic waves in ionized media related to aerospace applications

Altuntaş, Emre
The dominant natural electromagnetic (EM) radiation in the extremely low frequency (ELF) range is due to global lightning activity. Radio waves of ELF band traveling along the surface of the ground are able to circle the globe and return to the starting point. Schumann Resonances (SR) are the EM phenomena which occur in the cavity formed by the conducting Earth and the ionosphere, with peak frequencies close to 8, 14, 20, 26 Hz, etc. The spectral characteristics of the SR modes are defined by their resonant mode amplitudes, center frequencies and half-widths. The characteristics of the SR became important in aerospace, marine applications, atmospheric studies, in addition to their relevance to global lightning studies due to their frequency band. The objective of this work is two fold: (i) to investigate the characteristics of SR parameters obtained at Sarkoy in Turkey; (ii) to model the nonlinear characteristics of the Near Earth Space Processes by forecasting the 1st SR mode intensities different time steps in advance using neural network modeling approach. The results show that the SR amplitudes exhibit the characteristics of Tropical African lightning activity and have maxima around 1400 UT. The neural network results show that the proposed model is able to forecast SR amplitudes from 0,5 to 36 hours in advance within reasonable error limits. Furthermore, a fuzzy neural network model with a nonlinear optimization algorithm for the training phase is proposed and tested for the future work.


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Ballıkaya, Elif; Aydın Çivi, Hatice Özlem; Department of Electrical and Electronics Engineering (2007)
Method of Moments (MoM)/Green’s function formulation is developed for the analysis of electromagnetic radiation from planar rectangular microstrip antennas with different feeding techniques. Investigated structures are microstrip line fed patch antenna, proximity coupled patch antenna and slot coupled patch antenna. For all these structures equivalent problems are defined. Then, integral equations where currents are the unknowns are obtained from boundary conditions and by using spectral domain representati...
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Etiler, Burkay; Tuncer, Temel Engin; Department of Electrical and Electronics Engineering (2007)
In OFDM systems carrier frequency offset is observed due to Doppler shift and transmitter-receiver frequency mismatches. This offset induces ICI (Intercarrier Interference). In this thesis, repeated data methods and pilot-aided carrier frequency offset(CFO) estimation methods and windowing techniques are used to mitigate the frequency offset problem and a performance comparison is made between these ICI cancellation techniques. Repeated data methods use only half of the bandwidth for information transmissio...
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Haliloğlu, Onur; Yılmaz, Ali Özgür; Department of Electrical and Electronics Engineering (2006)
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Kurt, Sinan; Demir, Şimşek; Department of Electrical and Electronics Engineering (2007)
Frequency Modulated Continuous Wave (FMCW) radar has wide application areas in both civil and military use. The range resolution is a critical concept for these FMCW radars as for the other radar types. There are theoretical restrictions in the range resolution. In addition, the non-ideal properties of the modules used in the systems negatively affects the range resolution. The transmitter leakage, non-linear frequency sweep, FM to AM distortion and measurement errors are some of the critical non-ideal prop...
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Oruç, Sacid; Yıldırım, Nevzat; Department of Electrical and Electronics Engineering (2010)
In modern broadband microwave applications, receivers are very sensitive to interference signals which can come from the system itself or from hostile emitters. Electronically tunable bandstop filters can be used to eliminate these interference signals with adaptation to changing frequency conditions. In this thesis, electronically tunable bandstop filter design techniques are investigated for microwave frequencies. The aim is to find filter topologies which allow narrowband bandstop or ‘notch’ filter desig...
Citation Formats
E. Altuntaş, “Forecasting of the electromagnetic waves in ionized media related to aerospace applications,” M.S. - Master of Science, Middle East Technical University, 2007.