Analysis of koch fractal antennas

İrgin, Ümit
Fractal is a recursively-generated object describing a family of complex shapes that possess an inherent self-similarity in their geometrical structure. When used in antenna engineering, fractal geometries provide multi-band characteristics and lowering resonance frequencies by enhancing the space filling property. Moreover, utilizing fractal arrays, controlling side lobe-levels and radiation patterns can be realized. In this thesis, the performance of Koch curve as antenna is investigated. Since fractals are complex shapes, there is no well–established for mathematical formulation to obtain the radiation properties and frequency response of Koch Curve antennas directly. The Koch curve antennas became famous since they exhibit better frequency response than their Euclidean counterparts. The effect of the parameters of Koch geometry to antenna performance is studied in this thesis. Moreover, modified Koch geometries are generated to obtain the relation between fractal properties and antenna radiation and frequency characteristics.


Use of Asymptotic Waveform Evaluation Technique in the Analysis of Multilayer Structures With Doubly Periodic Dielectric Gratings
Gudu, Tamer; Alatan, Lale (Institute of Electrical and Electronics Engineers (IEEE), 2009-09-01)
The reflection and dispersion characteristics of multilayer structures that involve periodically implanted material blocks are obtained by using the MoM solution of the volume integral equation. The asymptotic waveform evaluation (AWE) technique is utilized to obtain a Pade approximation of the solution in terms of a parameter such as frequency or incident angle. The use of AWE technique enables a fast sweep with respect to the approximation parameter. Moreover, a robust method for extracting the dispersion...
Stabilization of integral-equation formulations for the accurate solution of scattering problems involving low-contrast dielectric objects
Ergül, Özgür Salih (Institute of Electrical and Electronics Engineers (IEEE), 2008-03-01)
The solution of scattering problems involving low-contrast dielectric objects with three-dimensional arbitrary shapes is considered. Using the traditional forms of the surface integral equations, scattered fields cannot be calculated accurately if the contrast of the object is low. Therefore, we consider the stabilization of the formulations by extracting the nonradiating parts of the equivalent currents. We also investigate various types of stable formulations and show that accuracy can be improved systema...
A comparative study on polygonal mesh simplification algorithms
Yirci, Murat; Ulusoy, İlkay; Department of Electrical and Electronics Engineering (2008)
Polygonal meshes are a common way of representing 3D surface models in many different areas of computer graphics and geometry processing. However, these models are becoming more and more complex which increases the cost of processing these models. In order to reduce this cost, mesh simplification algorithms are developed. Another important property of a polygonal mesh model is that whether it is regular or not. Regular meshes have many advantages over the irregular ones in terms of memory requirements, effi...
Derivation of length extension formulas for complementary sets of sequences using orthogonal filterbanks
Candan, Çağatay (Institution of Engineering and Technology (IET), 2006-11-23)
A method for the construction of complementary sets of sequences using polyphase representation of orthogonal filterbanks is presented. It is shown that the case of two-channel filterbanks unifies individually derived length extension formulas for complementary sequences into a common framework and the general M-channel case produces novel formulas for the extension of complementary sets of sequences. The presented technique can also be used to generate polyphase and multilevel sequences.
Analysis and design of microstrip printed structures on electromagnetic bandgap substrates
Güdü, Tamer; Alatan, Lale; Department of Electrical and Electronics Engineering (2008)
In the first part of the thesis, the 2-D structures in stratified media are analyzed using an efficient MoM technique. The method is used to optimize transmitted or reflected electric fields from the 2-D structures. The genetic algorithm is used in the optimization process. In the second part a 3-D MoM technique is implemented to analyze multilayered structures with periodically implanted material blocks. Using the method, the dispersion and reflection characteristics of the structure are calculated for dif...
Citation Formats
Ü. İrgin, “Analysis of koch fractal antennas,” M.S. - Master of Science, Middle East Technical University, 2009.