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Öğe A Hybrid Retrieval Method for an -Class Bianisotropic Metamaterial Using Scattering Parameter Method(Ieee-Inst Electrical Electronics Engineers Inc, 2025) Ozturk, Gokhan; Hasar, Ugur Cem; Kaya, Yunus; Korkmaz, Huseyin; Stoyanov, IvayloIn this study, a hybrid retrieval method is proposed to retrieve all terms in the electric and magnetic tensors (along with coupling tensors) of Omega-class bianisotropic metamaterial (MM) slabs using scattering (S-) parameters of both normal incidence TE2 mode and oblique incidence TM2 and TE modes. Compared with other extraction methods in the literature, our retrieval method fully characterizes the MM slab (extracts all constitutive parameters) without necessitating any numerical technique (non-iterative) using fewer wave configurations (two modes) and sample configurations (one configuration). Contrary to two sample configurations required in the application of previous retrieval methods in the literature, one sample configuration (with and without its rotation in the transverse plane) significantly decreases the effect of fabrication tolerances on the accuracy of extraction. The proposed extraction method is first validated by a bulk MM slab synthesized by the Lorentz and Drude models. Then, it is applied for extracting the electromagnetic properties of two bianisotropic MM slabs in the form of square split-ring-resonators and Omega-shape using their S-parameters simulated by a full wave simulation program. Finally, its accuracy is examined by comparing simulated S-parameters with those reconstructed by using extracted electromagnetic parameters. It is observed that our proposed method determines the constitutive parameters with a relatively higher accuracy in a relatively short amount of time.Öğe A Nested Square Shaped Metasurface-Based Broadband Linear Polarization Converter for Ku-Band Applications(2023) Kaya, YunusThis paper presents a wideband, thin, low-cost, and easy to fabricate linear polarization (LP) converter design utilizing metasurface (MS) for Ku-band (12-18 GHz) applications (also in the 18-19 GHz part of the K-band (18-27 GHz)). The design has a topology on a 1.6 mm thick FR-4 dielectric material with copper MS on the front and an entirely copper slab on the back. The presented design shows a polarization conversion ratio (PCR) of beyond 90% within the 12-19 GHz frequency band and also over 99% in the 12.5-13.1 and 16.32-17.64 GHz frequency ranges. To further give insight into the physical structure of the suggested MS-based polarization converter (PC), both the u – v axes are analyzed, and the existing surface behaviors at resonance frequencies are investigated. We compare the performance outputs with other Ku-band PCs, and the efficiencies of the suggested strategy over current MS-based LP converters are emphasizedÖğe Broadband Multilayer Absorber Design Using Double-Stage Cognitive Seeker Optimization Algorithm(Ieee-Inst Electrical Electronics Engineers Inc, 2025) Hasar, Ugur Cem; Kaya, Yunus; Korkmaz, Huseyin; Iliev, TeodorIn this paper, a double-stage cognitive seeker optimization (DSC-SO) algorithm is developed for evaluating optimum design parameters of broadband microwave absorbers. The algorithm not only gives freedom of selecting different number of layers and optimizing the order of layers and their thickness in different stages (double-stage) but also utilizes a cognitive search to improve the optimization. Contributions of the cognitive search and the two stages of our algorithm are first examined to show its efficiency. Then, its performance has been evaluated for two different optimization problems (a broadband absorber for one incidence angle and a broadband absorber with multiple incidence angles) in comparison with similar algorithms in the literature. It has been shown that our algorithm determines either fewer number of layers or smaller overall absorber thickness or both when compared with the results of other algortihms. Finally, the effect of fabrication tolerance is conducted to examine the importance of fewer number of layers.Öğe Broadband Soil Permittivity Measurements Using a Novel De-Embedding Line-Line Method(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Hasar, Hafize; Hasar, Ugur C.; Kaya, Yunus; Oztas, Taskin; Canbolat, Mustafa Y.; Aslan, Nevzat; Ertugrul, MehmetA new de-embedding line-line method has been proposed for accurate complex relative permittivity (epsilon(r)) determination of soil samples loaded into an EIA 1-5/8 '' coaxial transmission line measurement system. The method has three main features. First, it bypasses the requirement of calibration of this system by using only two identical coaxial lines with different lengths. Second, it does not need any numerical technique for epsilon(r) determination. Third, it does not require knowledge of electromagnetic properties and thickness information of the bead used for supporting soil samples. The method is next validated by simulations performed using a full 3-D electromagnetic simulation program (CST Microwave Studio) and by epsilon(r) measurement of a polyethylene (PE) material. Finally, epsilon(r) values of three air-dried and water-saturated soil samples having 90% or more sand content with different electrical conductivities (ECs) and gathered from different areas of the city Gaziantep in Turkey, were measured.Öğe Broadband, Stable, and Noniterative Dielectric Constant Measurement of Low-Loss Dielectric Slabs Using a Frequency-Domain Free-Space Method(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Hasar, Ugur C.; Kaya, Yunus; Ozturk, Gokhan; Ertugrul, Mehmet; Korasli, CelalA broadband, stable, and noniterative free-space method is proposed for dielectric constant epsilon'(r) determination of low-loss dielectric slabs from reflection-only measurements through simple calibration standards (reflect and air). It is applicable for dispersive samples and does not require thickness information. Simulations of nondisperive and dispersive samples are performed to validate our method. Dielectric constant measurements of polyethylene and polyoxymethylene samples (9-11 GHz) are carried out to examine the accuracy of our method.Öğe Calibration-Free Time-Domain Free-Space Permittivity Extraction Technique(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Hasar, Ugur C.; Ozturk, Gokhan; Kaya, Yunus; Ertugrul, MehmetA time-domain free-space technique has been proposed to extract relative permittivity (epsilon(r)) and effective conductivity (sigma(e)) of low-loss dielectric samples using their metal- and air-backed calibration-free reflected powers. Numerical computations and 3-D electromagnetic simulations were performed to validate the method. A sensitivity analysis was carried out to examine its accuracy. Calibration-free time-domain free-space measurements over 1-12 GHz were conducted by VNA to extract epsilon(r) and sigma(e) of polyethylene and polypropylene low-loss samples.Öğe Cheaper, Wide-Band, Ultra-Thin, and Multi-Purpose Single-Layer Metasurface Polarization Converter Design for C-, X-, and Ku-Band Applications(Mdpi, 2023) Kaya, YunusThis article presents the design of wide-band, ultra-thin, and multi-purpose polarization converter utilizing metasurface for C-, X-, and Ku-band applications. Having a topology on a FR-4 substrate with metasurface metallic patterns on the front and an all-metallic surface finish on the back, the unit cell of converter design has symmetry in the x-y plane with unique features of having both linear polarization (LP) and circular polarization (CP) property. While the polarization conversion ratio (PCR) of converter in normal incidence case is more than 90% in three different frequency bands of 6.46-6.78 GHz, 10.52-11.85 GHz, and 16.49-17.37 GHz, it shows linear-to-linear polarization feature and a linear-to-circular polarization feature with left-handed circular polarization (LHCP) for the frequency range between 7.28 and 9.40 GHz and right-handed circular polarization (RHCP) for the frequency range between 13.38 and 15.19 GHz. It is also seen that the converter has a PCR value of around 90% for oblique incidence case with incidence angles up to 45 & DEG;. Extensive simulations have been conducted to prove the performance of suggested converter with the aid of a commercially-available simulation platform, called CST Microwave Studio. The advantages of suggested polarization converter are low-cost, wide-band, ultra-thin, and having both LP and CP conversion in C-, X-, and Ku-bands.Öğe Complex Permittivity and Thickness Evaluation of Low-Loss Dielectrics From Uncalibrated Free-Space Time-Domain Measurements(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Hamdullah; Izginli, Mucahit; Barroso, Joaquim Jose; Ramahi, Omar M.; Ertugrul, MehmetA free-space time-domain method is proposed to retrieve dielectric constant (epsilon r), conductivity (sigma e), and thickness (d) of metal-backed low-loss dielectric samples using calibration-independent reflected power peak measurements. Its algorithm is validated by numerical calculations and simulations (CST Microwave Studio) using a sine-modulated Gaussian window. A sensitivity analysis is followed to examine its performance considering the dependencies of reflected power peaks with respect to epsilon r and sigma e. Free-space time-domain measurements have been implemented after transforming frequency-domain measurements into time-domain ones to extract epsilon r, sigma e, and d of polypropylene, polyethylene, and polyoxymethylene samples.Öğe Coupling analysis between resonating metamaterial slabs using scattering parameters(Elsevier Sci Ltd, 2021) Hasar, Ugur Cem; Kaya, Yunus; Izginli, Mucahit; Ozturk, Hamdullah; Ertugrul, Mehmet; Ramahi, Omar M.Metamaterial (MM) slabs in close proximity can couple with one another. This coupling can modify the electromagnetic response of the overall MM structure involving individual MM resonators. The signal flow graph technique along with the ABCD parameters are applied to quantitatively and qualitatively examine this coupling from simulated/measured scattering parameters of cascade connection of closely or largely separated MM slabs. S-parameter measurements of a MM slab constructed by split-ring-resonators were carried out at X-band (8.2-12.4 GHz) to validate our theoretical analysis.Öğe De-Embedding Technique for Parameter Extraction of Biaxial Bianisotropic Metamaterial Slabs(Ieee-Inst Electrical Electronics Engineers Inc, 2024) Hasar, Ugur Cem; Kaya, Yunus; Korkmaz, Huseyin; Iliev, TeodorAmong material classes of isotropic, anisotropic, bi-isotropic, and bianisotropic, the latter classis important because, as different from other classes, the bianisotropic class can describe complex behavior of various materials through tensor expressions between electric and magnetic fields via electric and magnetic flux densities. All electromagnetic parameters (a total of seven) of a general bianisotropic material need to be accurately extracted for understanding its response and characteristic. Extraction methods can be utilized for such a goal. However, the extraction methods in the literature either require a formal calibration procedure or are limited to the extraction of three electromagnetic parameters only. In this study, an attractive self-calibrating waveguide method has been devised for determination of electromagnetic parameters of biaxial biansiotropic metamaterial (MM) slabs. Its first advantage is that it uses a thru connection in addition to the MM-loaded line connection (three different configurations - Case A, Case B, and Case C) and empty-line connection next to the MM-loaded line connection to extract all (seven) constitutive parameters together with the magnetoelectric coupling coefficient. Its second advantage is that it relies on explicit expressions and does not require any calibration process for such an extraction. Simulations and uncalibrated scattering parameter waveguide measurements at X-band (8.2-12.4 GHz) were performed for a biaxial bianisotropic MM slab made by C-patterned resonators to validate the proposed method. It is observed that extracted electromagnetic parameters by the proposed method satisfy the passivity conditions over the entire frequency band except for a few frequency points or regions (e.g.,f=8.2 GHz). Its reason is expected to be associated with the difficulty in satisfying the continuous medium property at such frequencies. Besides, it is noted that two of the constitutive parameters (epsilon 2and mu 3) illustrate a thickness-resonance behavior revealed by additional measurements of the Case B - MM structure with different lengths (7.675 mm, 9.21 mm, and10.475 mm). Besides, it is noted that the resonance behavior of the Case C - MM structure changes with a change in periodicity. Specifically, when the periodicity in the x direction of this MM structure changes from approximately 3.26 mm to 2.29 mm, the resonance frequency shifts from nearly 10.43 GHz to 10.30 GHz(a 1.25% variation). Finally, sensitivity, uncertainty, and error analyses were also performed to evaluate and improve its accuracy. It is observed that|partial derivative epsilon 3/partial derivative|31AÖğe Determination of Propagation Constants and Wave Impedance of Non-Reciprocal Networks From Position-Insensitive Waveguide Measurements(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Hasar, Ugur C.; Kaya, Yunus; Izginli, Mucahit; Ozturk, Hamdullah; Barroso, Joaquim J.; Ramahi, Omar M.; Ertugrul, MehmetA microwave method is proposed to determine the forward and backward propagation constants (gamma ? and gamma ?) and the wave impedance ( $z_{w}$ ) of reciprocal and non-reciprocal microwave networks whose positions are not known within their measurement cells (position-insensitive). The proposed method relies purely on analytical expressions and can also evaluate the reference plane transformation distances. Scattering parameter measurements at the X-band (8.2-12.4 GHz) of a reciprocal network (a waveguide straight) and a non-reciprocal network (a microwave phase shifter) arbitrarily positioned into their measurement cells were conducted to retrieve gamma ?, gamma ?, and $z_{w}$ for validation of our method and testing its position-insensitive property. The importance of the method becomes apparent when compared to conventional methods whose accuracy is based on precise determination of the reference planes.Öğe DOĞU ANADOLU BÖLGESİNDE GENEL ARAZİ KULLANIMI VE BU KULLANIMDAN KAYNAKLANAN SORUNLAR; ELEŞKİRT-AĞRI ÖRNEĞİ(Bayburt University, 2007) Gümüş, İbrahim; Kırıcı, Muammer; Kurt, Murat; Kaya, YunusBu çalışma, Doğu Anadolu Bölgesinde (Eleşkirt-Ağrı) yapılmış olup, bölgede yapılan diğer araştırmalar ve gözlemler sonucu, tespit edilen yanlış arazi kullanımı ve buna bağlı olarak ortaya çıkan erozyon olgusu incelenerek çareleri ortaya konulmaya çalışılmıştır.Öğe Effect of sample deformation in longitudinal axis on material parameter extraction by waveguides(Elsevier Sci Ltd, 2021) Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Gokhan; Ertugrul, MehmetAn analysis was performed for examining the consequences of sample deformation in longitudinal axis in the sample-loaded non-resonant waveguide techniques. Vertical and horizontal deformations were first simulated to understand the change in field distributions and corresponding scattering parameters. Then, effects of sample length, dielectric constant, and loss factor for these deformations on extracted electromagnetic properties were analyzed using simulated results. Finally, S-parameter measurements were carried out to understand the effect of vertical deformation on permittivity results and to examine any improper sample preparation by hand-made and machine-made samples by applying a statistical model based on mean, standard deviation, coefficient of variation, and confidence interval. It was noted that extracted dielectric constants of each tested dielectric sample (polyethylene, polypropylene, polyvinyl-chloride) were within the confidence interval range of 90% while their retrieved loss factors were within the confidence interval range of 90%, 95%, or 98%.Öğe Elektrik Kaynaklı Yanma ve Yangın(Bayburt University, 2019) Kaya, Betül; Kaya, YunusBu çalışmada Türkiye ve Dünya'nın bazı bölgelerinde yangının en önemli sebeplerinden birisinin elektrik kaynaklı yangınlar olduğu üzerinde durulmuştur. Bu duruma bağlı olarak ise yanma ve yangının tanıtılmasından başlanarak, elektrikten kaynaklanan yangınlar hakkında temel bilgiler verilmiş ve elektrikten kaynaklanan yanma ve yangına karşı çeşitli önlemler sunulmuştur.Öğe Extraction Method for Unique Determination of Complex Permittivity From Graphical Analysis of Natural Frequencies(IEEE-Inst Electrical Electronics Engineers Inc, 2023) Hasar, Ugur C.; Ozturk, Gokhan; Kaya, Yunus; Alfaqawi, Mona S. S.; Barroso, Joaquim Jose; Ertugrul, Mehmet; Ramahi, Omar M.A time-domain free-space extraction procedure is proposed to uniquely determine the relative complex permittivity epsilon(r)(omega) based on two sets of natural frequencies of the metal- and air-backed dielectric samples. A graphical analysis is applied for evaluating whether unique epsilon(r)(omega) can be extracted using such natural frequencies. The method is numerically validated using two dielectric samples with different epsilon(omega) for the ideal case (no noise) and under the influence of noise with different signal-to-noise ratios (SNRs).Öğe Feasible Extraction Method for Electromagnetic Properties of Multilayer Metamaterials With Short-Circuit Termination(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Hasar, Ugur Cem; Ozturk, Gokhan; Kaya, Yunus; Bute, Musa; Karaaslan, Muharrem; Barroso, Joaquim J.; Ramahi, Omar M.An extraction technique is proposed for electromagnetic characterization of metal-backed multilayer metamaterial (MM) structures demonstrating reflection-asymmetric property. It uses recursive scattering parameters for direct and reversed configurations of a multilayer structure. The algorithm was validated by comparing the extracted electromagnetic properties of multilayer structures composed of different MM unit cells with those determined by one-layer-only S-parameter methods. Two-layer and three-layer multilayer structures composed of MM slabs with C-shaped and Omega-shaped rings and an FR4 material were fabricated and measured for experimental validation. A sensitivity analysis was also conducted to quantitatively evaluate the performance of our method against a small air gap between the multilayer structures and the short-circuit termination and between adjacent MM slabs within these structures. Strong agreement was observed between the resulted obtained using our method and measurements.Öğe Feasible Waveguide Method for Obtaining ElectromagneticProperties of Biaxial Bianisotropic Materials with Strong Magneto Electric Coupling(2021) Kaya, YunusIn this study, an easy-to-apply waveguide method is proposed for material characterization of biaxial bianisotropic samples withstrong magneto-electric coupling. Its underlying expressions are derived considering scattering (S-) parameters of the sample at onefixed orientation in two waveguides at their dominant modes with different cross sections. The method is validated by synthesized andretrieved electromagnetic properties of a sample when there is no/some noise.Öğe Graphical Method for Examining Complex Natural Frequencies of Dispersive Materials(IEEE-Inst Electrical Electronics Engineers Inc, 2021) Hasar, Ugur C.; Ozturk, Gokhan; Barroso, Joaquim J.; Gurbuz, Tolga U.; Kaya, Yunus; Ertugrul, MehmetA graphical method is extended to and applied for visual inspection of solution patterns (region of complex natural frequencies sn) in the complex s-plane for dispersive materials characterized by the Debye and Lorentz models. These patterns are in the form of exponential decay and C-shaped profiles for the Debye and Lorentz models, respectively. Their forms are observed to be affected (e.g., moving left/right) in different manners with a variation of dispersion parameters. This method, thanks to its visual inspection capability, can help in analyzing/synthesizing filters and frequency-selective surfaces.Öğe Honey-Water Content Analysis by Mixing Models Using a Self-Calibrating Microwave Method(IEEE-Inst Electrical Electronics Engineers Inc, 2023) Hasar, Hafize; Hasar, Ugur C.; Kaya, Yunus; Ozturk, Hamdullah; Izginli, Mucahit; Oztas, Taskin; Aslan, NevzatMicrowave techniques, as an indirect approach, can be applied for analyzing water content in honey by way of permittivity measurements. However, these techniques require proper calibration to accurately perform such indirect evaluation. Improper calibration standards used in this calibration process could naturally result in a reduction in the accuracy and thus the performance of dielectric characterization using microwaves. Self-calibrating microwave techniques can reduce the effects of imprecise standards and thus improve the performance of microwave measurements by bypassing the requirement of calibration standards. In this study, we develop a self-calibrating microwave measurement technique to determine the relative permittivity of honey samples and implement binary mixing models to predict adulteration levels of water-adulterated honey. From this implementation, it is observed that the parallel-capacitance mixing model could efficiently be applied to determine the concentration of water adulteration by examining the differences between absolute values of the real parts of the measured and predicted complex permittivities of adulterated honey.Öğe Honey-Water Content Analysis by Mixing Models Using a Self-Calibrating Microwave Method(Institute of Electrical and Electronics Engineers Inc., 2023) Hasar, Hafize; Cem Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Hamdullah; Izginli, Mucahit; Öztaş, Taşkin; Ramahi, Omar MustafaMicrowave techniques, as an indirect approach, can be applied for analyzing water content in honey by way of permittivity measurements. However, these techniques require proper calibration to accurately perform such indirect evaluation. Improper calibration standards used in this calibration process could naturally result in a reduction in the accuracy and thus the performance of dielectric characterization using microwaves. Self-calibrating microwave techniques can reduce the effects of imprecise standards and thus improve the performance of microwave measurements by bypassing the requirement of calibration standards. In this study, we develop a self-calibrating microwave measurement technique to determine the relative permittivity of honey samples and implement binary mixing models to predict adulteration levels of water-adulterated honey. From this implementation, it is observed that the parallel-capacitance mixing model could efficiently be applied to determine the concentration of water adulteration by examining the differences between absolute values of the real parts of the measured and predicted complex permittivities of adulterated honey. © 1963-2012 IEEE.
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