Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.Kuştepeli, Alp

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Now showing 1 - 4 of 4
  • Master Thesis
    Novel Microstrip Antennas for Multiband Wideband Applications
    (Izmir Institute of Technology, 2014) Bozdağ, Göksenin; Kuştepeli, Alp; Kuştepeli, Alp; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this study, four novel microstrip antennas are designed for various wireless systems in two different types which are log periodic dipole array and planar monopole. In the first design, multiband behavior of standard printed log periodic dipole array antenna is converted to wideband by employing sub-sectional tapered feeding and the operating bandwidth is increased by using a feed point patch. By the way, the proposed antenna becomes capable of GPS (L1 and L2), PCS, IMT-2000, WLAN, WiMAX, UWB and X Band systems. The other designs are printed planar monopole antennas which have small size and low group delay. Microstrip inset feeding, sectional design and slot loading methods are basically used for these antennas. First printed planar monopole antenna is designed for WLAN, WiMAX, UWB and X Band applications by employing inset feeding and sectional design. In the second and the third printed monopole designs, slot loading technique is also employed. It provides both exciting extra resonance frequencies and keeping S11 performance below -10 dB level. In the second design, a novel slot geometry is implemented on the first printed monopole design for PCS band. Then, desired frequency resonance with required bandwidth is reached and the antenna becomes capable of PCS in addition to UWB and X Band. In the third design, another novel slot geometry is also implemented on the first printed monopole design for GPS band. Consequently, the antenna becomes capable of GPS in addition to WLAN, WiMAX, UWB and X Band.
  • Master Thesis
    Novel rectangular spiral antennas
    (Izmir Institute of Technology, 2008) Saynak, Uğur; Kuştepeli, Alp; Kuştepeli, Alp; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Round spiral antennas are generally designed by using Archimedean spiral geometries which have linear growth rates. To obtain smaller antennas with nearly the same performance, square spiral Archimedean geometries are also widely used instead. In this study, novel square antennas are proposed, designed and examined. At first two similar but different approaches are employed to design new antennas by considering the design procedure used to obtain log-periodic antennas. Then, the performance of these antennas is improved by considering another property of log-periodic antennas. Simulations are performed by using two different numerical methods which are Finite Difference Time Domain Method (FDTD) and Method of Moments (MoM). The results obtained from the simulations are compared with those of the Archimedean spiral antennas in terms of the frequency dependency of fundamental antenna parameters such as antenna gain and radiation pattern. The simulation results are compared with the ones obtained from the experimental study.
  • Master Thesis
    Fibonacci fractal tree antennas
    (Izmir Institute of Technology, 2004) Özbakış, Başak; Kuştepeli, Alp; Kuştepeli, Alp; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Fractal geometry is first defined by Benoit Mandelbrot. A fractal structure is generated with an iterative procedure of a simple initiator by replicating many times at different scales, positions and directions. Fractal structures generated with this method are generally self-similar and the dimensions of these structures cannot be defined with integers. Koch, Minkowski and Sierpinski structures are the most known fractal structures. These structures are commonly used as multiband and wideband antenna designs because of the self-similarity. Furthermore, their special geometry is useful to obtain small antennas which are resonant at lower frequencies. Lowering the resonant frequency has the same effect as miniaturizing the antenna at a fixed resonant frequency. Other important and interesting fractal structures used in antenna designs are the various types of the fractal trees. However, in recent studies the branch length ratios of the fractal tree antennas are taken constant. In this study fractal tree antennas with nonuniform branch length ratios are investigated. By changing the geometry and number of branches of the fractal tree structures the antenna characteristics are examined. The branch lengths and number of branches of the fractal tree antennas are determined by using the Fibonacci sequence. Leonardo Fibonacci (1170 - 1240), a famous Italian mathematician, dealt with geometry and developed a number sequence while observing the nature. Fractal tree antennas are designed with two different geometries in order to improve the resonance behavior of the antennas. The number of branches is decreased, so that less complex fractal tree antennas with the similar performance can be obtained.
  • Master Thesis
    Design and Calibration of a Tem Stripline for Electromagnetic Compatibility Testing
    (Izmir Institute of Technology, 2011) Hilavin, Sezgin; Kuştepeli, Alp; Kuştepeli, Alp; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Electrical products are used in every aspect of our lives. Every electrically device has the potential of causing unintentional interference to other electrical devices. All unwanted currents or voltages that may arise in a system generate electrical noise. All kinds of unexpected radio-frequency (RF) energy produce this kind of noise. The term Electromagnetic Interference --EMI -- describes the situation that electrical noise destroys the functionality of systems. Therefore, emissions and immunity tests have to be performed according to the harmonized European norms like EN55020 standard. In this thesis, immunity to radiated fields testing will introduce and the basic requirements of the suggested test site which is a TEM stripline will also be mentioned. Stripline is a transmission line construction which provides a uniform electromagnetic field between its parallel plates. Radiated immunity can be defined as the product's ability to withstand EM energy that arrives via free-space propagation for its functionality. Design of a new TEM stripline for EMC testing is given in order to construct an alternative test site, a new stripline bigger than the one given by the standard was built. Main attention has been focused on the design parameters (characteristic impedance, field uniformity etc.) and calibration of the designed stripline. Defined stripline in the standard has 80 cm height but it is not sufficient for big equipments under test (EUTs). Then an alternative stripline can be used if it fulfills the specifications required by the standard.