Design and development of electromagnetic wave absorbing composites effective at microwave frequencies /

Hamat, Özgür
In the scope of this study, EM wave absorbing composites effective at microwave frequencies having crucial properties for their structural applicability will be designed and developed making use of a novel approach originating from our research group. For this purpose, surfaces of glass and polymeric fiber woven fabrics were modified via metal coatings with nm order thickness, where EM wave absorbing structural composites were formed by incorporating multilayered combinations of these surface-modified woven fabrics within polymer matrices. EM wave reflection and transmission properties, and hence absorption characteristics of surface-modified single layer and multilayer fiber woven fabrics were investigated using Free-Space test method. Based on the experimental data achieved on single layer woven fabrics, simulation studies were conducted in order to predict the EM wave absorption characteristics of multilayered reinforcement structures. In the last phase of the study, structural prototype EM wave absorbing polymer matrix composite is produced by placing surface modified multilayer fiber woven reinforcement materials with the highest EM wave absorption. More than 90% EM wave absorption was achieved with the fabricated composites in 18-40 GHz frequency range. Critical design principles required to reach to this challenging target were presented using simulations and experimental studies.


Countermeasure methods for high power microwave pulses /
Keskin, Muharrem; Demir, Şimşek; Department of Electrical and Electronics Engineering (2014)
In this thesis, a limiter structure is investigated to decrease the effects of High Power Microwave (HPM) pulses coupled from front-door by using vanadium dioxide (VO2). To prove that vanadium dioxide can be used as an RF limiter, this structure is examined, realized and measured. Firstly, susceptibility of LNA to HPM pulses is investigated by an experimental setup to determine the destruction threshold levels of LNA technology for direct injection of HPM pulses. Based on these threshold levels, diode limit...
Design and realization of high power low loss combiners
Suna, Gonca; Yıldırım, Nevzat; Department of Electrical and Electronics Engineering (2013)
In recent high power microwave systems, power generation is commonly achieved by combining a bunch of transistor amplifier. Regarding the efficiency of power combining operation, insertion loss of the combiner is a critical parameter. In this thesis, several low loss power combiners, namely, microstrip Wilkinson combiner in 6-18 GHz frequency range, suspended stripline branchline couplers in 16.5-17.5 GHz frequency range and finally, planar probe coaxial waveguide combiners in 8.5- 11.5 GHz and 15.5-17.5 GH...
Development of D -type fiber optic sensors for detection of refractive index variation in evanescent wave field /
Güleryüz, Burcu; Durucan, Caner; Aslan, Mustafa M.; Department of Metallurgical and Materials Engineering (2014)
The purpose of this study is to design, construct, develop and test D-type multimode fiber optic (F/O) sensors based on evanescent wave field sensing. A comprehensive work has been performed both theoretically and experimentally using a geometrical modification approach to improve the sensors response in different manners for detecting the refractive index (RI) variations and bio-molecular interactions in aqueous environment. In this study, the D-type F/O sensors performance was improved utilizing optical w...
Design and implementation of magnetic field sensors for biomedical applications /
İnan, Ulaş Can; Gençer, Nevzat Güneri; Department of Electrical and Electronics Engineering (2015)
In this work, firstly the magnetic sensor types and their feasibility for biomedical applications are investigated. Then the air-cored induction coil sensor is chosen due to its advantages. Afterwards the usage of induction coils combined with amplifiers and connection types are studied. The biomedical applications requiring the use of magnetic field sensors are introduced. One of them, Lorentz Field Electrical Impedance Tomography (LFEIT) is explained in detail and experimental work is done for this applic...
Design and Optimization of Nanoantennas for Nano-Optical Applications
Işıklar, Göktuğ; Ergül, Özgür Salih; Department of Electrical and Electronics Engineering (2020-9)
In this study, design and simulation of plasmonic nanoantenna structures to obtain high power enhancement capabilities at optical frequencies, as well as utilization of nanoantennas for imaging and sensing applications are presented. Plasmonic characteristics of nanoantennas, which depend on many parameters, such as material, frequency, geometry, and size, are investigated in detail via computational analyses of various nanoantenna structures. Numerical solutions of electromagnetic problems are performe...
Citation Formats
Ö. Hamat, “Design and development of electromagnetic wave absorbing composites effective at microwave frequencies /,” M.S. - Master of Science, Middle East Technical University, 2014.