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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 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 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 Easy-to-Implement Ultra-Thin, Wide-Band, and Multi-Functional Polarization Converter for K and Ka Band Applications(Wiley-V C H Verlag Gmbh, 2022) Coskun, Aykut; Hasar, Ugur Cem; Ozmen, Ahmet; Ertugrul, MehmetThis article presents an ultrathin, broadband, and multipurpose polarization converter design utilizing an anisotropic metasurface for K and Ka band. The proposed polarization converter, which has a single layer F4B as a substrate material with hexagonal-shaped metallic solid structure along with hexagonal ring with diagonal splits on its front surface and a background (a completely metallic surface) on its back, works as not only a circular polarization converter but also a linear polarization to circular polarization (LP to CP) converter. Its polarization conversion rate (PCR) is more than 90% in the frequency range from 17.87 to 43.15 GHz, covering all of the K and Ka bands with a relative bandwidth of 83% under normal incidence case. For incidence angles up to 40 degrees, PCR is observed to be greater than 75% in almost all of the K and Ka bands (except for the frequency range between 24.72 and 27.11 GHz). Furthermore, the proposed design has LP to CP in two different frequency bands, 16.23-16.74 GHz and 48.6-48.8 GHz. The proposed polarization converter, as advantages, is low cost, ultra thin, broadband, and facile, which can be useful in linear cross polarization conversion in K and Ka band applications.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 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 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 Improved Method for Permittivity Determination of Dielectric Samples by Free-Space Measurements(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Hamdullah; Izginli, Mucahit; Ertugrul, Mehmet; Barroso, Joaquim Jose; Ramahi, Omar M.A new deembedding technique is proposed for relative complex permittivity epsilon(r) determination of dielectric materials using gated free-space measurements. Its three main features are 1) it does not require any formal calibration procedure (calibration-free); 2) it is position-insensitive; and 3) it extracts ripple-free epsilon(r) due to gating process. The objective function derived to determine epsilon(r) by the proposed method is validated by free-space measurements of three dielectric samples (polypropylene, polyethylene, and polyoxymethylene). Besides, the accuracy of our method is compared with the accuracy of other calibrationfree and calibration-dependent methods in the literature.Öğe Measurement of Propagation Characteristics of Nonreciprocal Networks/Lines Using a Line-Line Method(IEEE-Inst Electrical Electronics Engineers Inc, 2021) Hasar, Ugur C.; Kaya, Yunus; Ertugrul, MehmetIn this article have proposed a new calibration-free line-line method for propagation constant (gamma) determination of homogeneous nonreciprocal networks or lines with symmetric reflection property. To achieve our goal, wave-cascading matrices for impedance, amplitude, and phase changes for a line step from a homogeneous reciprocal network or line to a homogeneous nonreciprocal network or line (and vice versa). Two different approaches based on the proposed line-line method are proposed for unique extraction of gamma in forward and backward directions. Measurements of gamma for two reciprocal lines (waveguide straights at X-band and Ku-band with different lengths) and a nonreciprocal line (microwave phase shifter) were first carried out and then compared with measured gamma of these lines by different methods to validate our method and monitor its accuracy.Öğe New formalism for characterization of simple non-reciprocal networks free from singularity-point problem(Elsevier Sci Ltd, 2021) Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Gokhan; Ozturk, Hamdullah; Izginli, Mucahit; Ertugrul, MehmetA method has been proposed for accurate characterization of non-reciprocal networks without enforcing the passivity principle. Thanks to the introduced different even and odd coefficients, our method has no singularity-point problem as compared with the conventional method. The proposed method is validated by scattering parameter measurements of a ferrite-loaded waveguide shifter. In addition, it is demonstrated by measurements that our method, as compared with the conventional one, is more resistant to random noise due to post-calibration effects.Öğe Parameter extraction method for reflection-asymmetric bianisotropic metamaterial slabs using one-port measurements(Elsevier Sci Ltd, 2023) Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Hamdullah; Ertugrul, Mehmet; Ramahi, Omar MustafaAn effective microwave method is developed for extracting electromagnetic properties of bianisotropic metamaterial (MM) slabs. As a non-iterative method, it utilizes only the one-port (air-backed and metal -backed MM slab) scattering (S-) parameter measurements. This is a useful feature especially for vector network analyzers, such as MS46131A, MS46121B, and R60, performing only one-port S-parameter measurements. Electromagnetic properties of a bianisotropic MM slab formed by C-shaped resonators are measured by an X -band (8.2-12.4 GHz) rectangular waveguide setup. The effect of any gap between the short-circuit termination for metal-backed measurements and the end of the MM slab on extracted electromagnetic properties is also examined for evaluating the possible error for proposed method.Öğe Parameter Retrieval of Samples on a Substrate From Reflection-Only Waveguide Measurements(IEEE-Inst Electrical Electronics Engineers Inc, 2021) Hasar, Ugur Cem; Ozturk, Hamdullah; Kaya, Yunus; Izginli, Mucahit; Ertugrul, MehmetA microwave method has been proposed for constitutive parameters' extraction of samples on a known substrate. The advantage of this method is that it relies on noniterative reflection-only (air- and metal-backed) scattering (S-) parameters so that it is a good candidate for the characterization of samples when only one-port measurements are available. It is validated by the X-band (8.2-12.4 GHz) waveguide S-parameter measurements. A sensitivity analysis is followed to evaluate and improve the performance of our method.Öğe Photocatalytic activity of cobalt aluminate nanoparticles synthesized by microwave-assisted combustion method(Pergamon-Elsevier Science Ltd, 2022) Karakas, Ibrahim Hakki; Karakas, Zeynep Karcioglu; Ertugrul, MehmetCobalt aluminate is one of the most widely-used spinet aluminate types. It is known that various structural, magnetic and morphological properties of spinet ceramics can vary depending on the synthesis technique and the starting chemicals used. In this study, initially, heat treatment was applied to cobalt aluminate nanoparticles synthesized by the microwave-assisted combustion method and the effects of the applied heat treatment on the structural properties were investigated. Characterization studies showed that cobalt aluminate spinet pigments were successfully synthesized. The optimum heat treatment temperature was determined as 700 degrees C. Then, the synthesized cobalt aluminate nanoparticles were used as photocatalysts for dye removal by photocatalytic oxidation from a synthetic wastewater containing Astrazon red textile dye and their photocatalytic activity was investigated at different catalyst dosages. Moreover, the same particles were also produced by conventional combustion technique. Then, their photocatalytic activities were studied and the data were compared with the results obtained from the experiments made with the samples produced with microwave assisted combustion method under the same experimental conditions. The results show that cobalt aluminate nanoparticles synthesized by microwave assisted combustion exhibit a better photocatalytic activity. In experiments performed with samples produced via microwave-assisted combustion method, all dyestuff content in the solution containing 50 mg/L dye was completely removed under UV irradiation for approximately 60 min. It was determined that the catalyst dosage had an effect on the reaction rate and the reaction was found to be compatible with the pseudo first order kinetic model.Öğe Propagation constant measurements of reflection-asymmetric and nonreciprocal microwave networks from S-parameters without using a reflective standard(Elsevier Sci Ltd, 2020) Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Gokhan; Ertugrul, MehmetWe propose a simple method for determination of forward and backward propagation constants of non reciprocal uniform networks or lines with asymmetric reflections. The wave cascading matrix presentation is used to diagonalize and decompose the line in terms of impedance and amplitude/phase transitions. The proposed method uses scattering parameters of the line/network connection and the thru connection, thus eliminating errors arising from fabrication tolerance and thickness of the second line. Besides, compared with conventional methods which necessitate calibration techniques such as the thru-reflect-line, our method has the advantage that it determines propagation constants without resorting the measurement of any reciprocal reflective standard. Propagation constant measurements of a reciprocal network (different-length X-band waveguide straights) and a nonreciprocal network (microwave phase shifter) were first carried out and then compared with those measured by different methods to validate and monitor the accuracy of our method. (C) 2020 Published by Elsevier Ltd.Öğe Simple and Accurate Electromagnetic Characterization of Omega-Class Bianisotropic Metamaterials Using the State Transition Matrix Method(IEEE-Inst Electrical Electronics Engineers Inc, 2021) Hasar, Ugur C.; Ozturk, Gokhan; Kaya, Yunus; Barroso, Joaquim J.; Ertugrul, MehmetWe propose a simple and accurate microwave extraction procedure for full electromagnetic characterization of Omega-class bianisotropic metamaterial (MM) slabs from normal incidence scattering (S-) parameters using TE1, TE2, and TE3 modes. Its closed-form nature (no need for any numerical analysis and optimization toolbox) and less requirement (a total of seven S-parameters) demonstrate the advantage of our method over other methods in the literature. Our approach was validated and its accuracy was verified by S-parameters, through a full electromagnetic simulation program-CST Microwave Studio, of an edge-coupled Omega-class split-ring-resonator MM slab.Öğe Temporal Reflection Response of Plane Waves Within an N-Layer Structure Involving Bianisotropy(IEEE-Inst Electrical Electronics Engineers Inc, 2023) Hasar, Ugur C.; Ozturk, Gokhan; Kaya, Yunus; Barroso, Joaquim Jose; Ertugrul, Mehmet; Ramahi, Omar M.; Alfaqawi, Mona S. S.The temporal reflection response of an N-layer composite structure involving bianisotropic behavior is examined for the first time in the literature. Toward this goal, the wave matrix (WM) method, which is fundamental, relatively easier to apply, and compact and iterative suitable for analysis of multilayer structures, is first extended to the analysis of an interface separating two different media involving bianisotropy. Next, the reflection response of the whole structure is derived in terms of series form to better analyze its temporal behavior. Then, frequency-domain and time-domain responses of the whole structure are expressed using a special reflection coefficient (the reduced reflection coefficient) by way of the concept of subregions. A numerical analysis is performed to demonstrate the applicability of our formalism for two different polarization types (perpendicular and parallel).Öğe Wideband Polarization Conversion Based on Elliptical-Shaped Metasurface for X-Band Applications(2023) Coşkun, Aykut; Teber, Ahmet; Ertugrul, MehmetHere, a single-layer, ultra-thin, multi-functional and high efficiency meta-surface is presented to perform wideband reflective linear (LP) and circular polarization (CP) transformations. The proposed meta-surface behaves as an excellent cross polarization converter for linear polarized wave over the relative absorption bandwidth (RAB) of 55.2% (7.89–13.91 GHz) with more than 97% efficiency. It successfully converts linearly polarized waves into circularly polarized waves in the 7.2–7.36 GHz frequency range. In addition, its polarization conversion rate (PCR) efficiency characteristics for TE and TM modes are retained across the entire X band, with a wide incidence angle up to $45^0$. The presented polarization converter has ultra-thin feature with 0.07?0 thickness. Due to its compact size, angular stability, high efficiency, simple structure and multi- functionality, this polarization converter is an important candidate for polarization manipulation and communication devices in many applications.
