Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2026Scopus SJRQ1Permittivity Extraction of Electrically Thin Samples by Reflection-Only Free-Space Measurements
Hasar, Ugur C.; Xue, Bing; Ozturk, Hamdullah; Kaya, Yunus; Ozturk, Gokhan
A permittivity extraction procedure is devised for electrically thin samples from reflection-only free-space measurements. Unlike previous studies, this procedure relies on sample-back metal termination measurements especially useful for thinner samples. An objective function independent of antenna transmission characteristics and reference plane position is derived. Minimum and maximum thickness and permittivity values for which our method is applicable are also examined. Free-space measurements at X-band (8.2-12.4 GHz) of a Rogers 4350B sample (approx 1.52 mm) and a FR4 sample (1.60 mm) were performed to validate our method with a dielectric constant less than 5% variation.
AtıfScopus1WoS1
İncele - MakaleAçık Erişim2026Scopus SJRQ1Determination of complex permittivity of a thin low-loss dielectric sample using state-space approach from waveguide measurements
Hasar, Ugur C.; Ali, Husain; Kaya, Yunus
An extraction procedure is proposed for relative complex permittivity () determination of thin low-loss samples positioned/deposited on a supporting substrate material using waveguide non-resonant microwave measurements. Its substrate thickness and sample thickness independence makes it unique extraction method in comparison with the available retrieval methods which are free from either substrate thickness information only or sample thickness information only. Its theoretical model is constructed on the state-transition matrix and state vector through which the link between and measured scattering (S-) parameters is established. Compared with previous works in the literature, a closed form (explicit) expression of is derived for a two-layer (sample on a substrate material) composite structure, thereby eliminating any numerical analysis or tool. Numerical analyses are implemented for validation of the proposed method as well as assessing the effect of noise and any possible air gap between the sample and its substrate. X-band ( GHz) waveguide measurements of a thinner (around 1.00 mm) polyvinyl chloride (PVC) for different measurement scenarios and measurements of a thin zinc oxide film (m) were performed to evaluate the performance of the proposed extraction method against other similar methods in the literature. Our method can find applications for characterization of thin-film, radar-absorbent material coatings, anti-corrosive paints, or thermal barrier coatings where sample thickness (and substrate thickness) can vary from one sample to another from the same batch.
- MakaleYalnız künye2026Scopus SJRQ1Reference-Invariant Permittivity Determination of Low-Loss Solid Dielectric Samples Using Spectral Free-Space Measurements Without Prior Thickness
Hasar, Ugur C.; Ali, Husain; Kaya, Yunus
An extraction method has been proposed for relative permittivity determination εrs of low-loss solid dielectric samples using free-space measurements. It relies on a reference-plane invariant expression with no thickness information a priori, making resistant to conventional free-space measurement errors which may arise from improper information of sample position and thickness. In addition, the method constructed by the state transition matrix (STM) uses closed-form expressions – a feature distinguishes our method from previous STM-based extraction methods requiring a numerical tool or optimization procedure. Furthermore, provided that the sample thickness L is evaluated, as a by-product, first using the derived closed-form objective function away from any thickness-resonance region, the proposed method then determines εrs and L free from thickness-resonance effect, which otherwise can introduce ripples around or at the thickness-resonance frequency. Numerical analysis is performed to validate and assess the performance of our method. Free-space measurements at X-band of two low-loss samples with substantial thickness are performed for validation and accuracy comparison of our method against other similar methods.
- MakaleAçık Erişim2026Scopus SJRQ1Permittivity extraction of sandy soils through uncalibrated and thickness-independent meniscus-free measurements using a hollow coaxial line
Hasar, Ugur C.; Korkmaz, Huseyin; Kaya, Yunus
Measurement techniques for accurate moisture level determination of various soil conditions are becoming popular in recent studies. Microwave-driven techniques, as positioned into indirect methods, could be tailored for precise and real-time detection of soil moisture. However, improper implementation of calibration techniques or usage of imperfect calibration standards required for precise measurements by these techniques presents a challenging limitation for their widespread usage. Besides, meniscus formation on top of soil samples with a sufficient moisture level could adversely influence the performance of these techniques. In this study, we present a microwave extraction method for eliminating the requirement of a formal calibration procedure and additionally removing the effect of meniscus on measurements through relative measurements of sandy soil samples while maintaining accurate permittivity extraction with no information of sample thickness. To achieve our goal, a mathematical framework unifying wave-cascading matrix and state-transition matrix presentations is proposed for permittivity determination from three measurement configurations (empty line, the (sandy) soil sample sandwiched between two identical plugs, and a shifted version of this plug-sample-plug configuration) and their inverses implemented by port switching operation. The proposed method is first validated by permittivity measurements of two liquid samples (distilled water and methanol). Then, permittivity measurements of two sandy soil samples (having more than 90% sand content) were conducted using Type-N-to-EIA 1-5/8” coaxial lines (with no universal calibration standard) over 0.05 GHz–3.0 GHz. From these measurements, it is noted that our meniscus-free method determines permittivity with a maximum absolute difference of 3.4% (evaluated from five independent measurements) while another similar method, suffering from meniscus presence, extracts permittivity with a maximum absolute difference of 4.0%. This indicates a clear advantage of our method for measurements of sandy soil samples having meniscus formation. We then utilized to construct a calibration curve, compared with other calibration curves using by other methods, allowing prediction of moisture volume content () of the tested sandy soil samples from measured permittivity data whose conformity analysis implemented by the three-pole Debye model and the Mironov-Fomin model. It is observed that this calibration curve could be utilized to predict within margin from measured permittivity data.
- MakaleAçık Erişim2025Scopus SJRQ1Broadband Multilayer Absorber Design Using Double-Stage Cognitive Seeker Optimization Algorithm
Hasar, Ugur Cem; Kaya, Yunus; Korkmaz, Huseyin; Iliev, Teodor
In 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.
AtıfScopus3WoS1OpenAlex3İncele - MakaleAçık Erişim2025Scopus SJRQ1A Hybrid Retrieval Method for an Ω-Class Bianisotropic Metamaterial Using Scattering Parameter Method
Ozturk, Gokhan; Hasar, Ugur Cem; Kaya, Yunus; Korkmaz, Huseyin; Stoyanov, Ivaylo
In this study, a hybrid retrieval method is proposed to retrieve all terms in the electric and magnetic tensors (along with coupling tensors) of Ω -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 Ω -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.
AtıfScopus2WoS1İncele - MakaleAçık Erişim2025Scopus SJRQ1Soil Permittivity Extraction by Time-Domain Free-Space Calibration-Free Microwave Measurements With No Thickness Information
Hasar, Ugur Cem; Korkmaz, Huseyin; Kaya, Yunus; Iliev, Teodor
An attractive microwave free-space method is proposed for permittivity extraction of soil samples using calibration-free time-domain measurements. Different from other similar methods in the literature which use the layer-stripping approach in the forward direction in the extraction process, its formalism is based on the layer-stripping approach in the backward direction, whereby allowing extraction of permittivity from interfacial reflection coefficient only without resorting to any thickness information, especially useful for time-domain analysis of multilayer structures having multiple reflection terms. Effects of angle misalignment, loss, and surface roughness on the extraction performance of the proposed method (PM) are analyzed by numerical examples. Permittivity measurements of three low-loss flat solid samples [polypropylene (PP), polyethylene (PE), and polyoxymethylene (POM)] were first performed by a free-space setup operating over 1–18-GHz frequency range to validate our methodology and compare its accuracy against other similar methods in the literature. Thereafter, permittivity measurements of two soil samples sieved with similar and different sizes (coarse- and fine-grained soil samples) by the same free-space setup were then considered to assess the applicability and performance of our method for electromagnetic property analysis of homogeneous and partially inhomogeneous soil samples.
AtıfScopus9WoS6OpenAlex8İncele - MakaleAçık Erişim2025Scopus SJRQ1Transient Plane Wave Transmission Through an N-Layer Multilayer Structure with Bianisotropic Behavior
Cem Hasar, Ugur; Kaya, Yunus; Korkmaz, Huseyin; Iliev, Teodor
An analysis based on electromagnetic reflection and transmission properties of multilayer structures are in general needed to get more information about their electromagnetic responses before their implementation for some specific applications involving absorption, shielding, and diagnosis. Such an analysis could be exercised by either frequency-domain or time-domain. While the former one is based on the steady-state response, the latter one is based on the transient response which thus provides more information about electromagnetic properties of multilayer structures. A procedure relying on a direct theoretical time-domain analysis is preferable to a time-domain analysis based on computational procedures such as the finite-time-difference-domain or the fast Fourier transform. In this study, a series presentation of transient plane wave transmission coefficient of N-layer composite structures involving bianisotropic behavior is derived for the first time in the literature in terms of reduced transmission coefficients (the concept of subregion). The wave matrix approach is applied for the theoretical analysis of the reduced transmission coefficient after application of the concept of subregion. Implementation of this concept to our problem is presented step-by-step to make a clear understanding of its application to bianisotropic multilayer structures. The derived reduced transmission coefficient is validated by different multilayer structures (different layer numbers, different layer lengths, and different polarizations) composed of individual layers whose electromagnetic responses are synthesized by the Lorentz dispersion model. Advantages and limitations of the derived formalism are also presented.
- MakaleYalnız künye2025Scopus SJRQ1Multi-functional, multi-band, low-profile, ultra-thin, and cost-effective metasurface-based polarization converter
Kaya, Yunus; Hasar, Ugur Cem; Ozturk, Hamdullah; Ozturk, Gokhan
This article presents a polarization converter (PC) that demonstrates linear polarization (LP) to LP (LP–LP), circular polarization (CP) to CP (CP–CP), and LP to CP (LP–CP) conversion performance in microwave C-band (4–8 GHz), X-band (8–12 GHz), Ku-band (12–18 GHz), and K-band (18–27 GHz). The designed converter performs LP–LP conversion in the frequency ranges of 6.414–6.771 GHz, 10.681–12.160 GHz, and 18.093–19.045 GHz, CP–CP conversion in the same frequency ranges (6.414–6.771 GHz, 10.681–12.160 GHz, and 18.093–19.045 GHz), and LP–CP conversion in the frequency ranges of 7.374–9.414 GHz and 13.792–16.777 GHz. It is single-layer, metasurface-based, reflection-type (because it consists of a metasurface-substrate-metal ground adaptation), multi-band (five bands), multi-functional (because it shows all three LP–LP, LP–CP, and CP–CP conversions), ultra-thin (with a substrate thickness of 1.6 mm (0.034λ)), low-profile, and cost-effective (since relatively cheaper and easily available FR4 dielectric material is used). Simulations for the designed PC have been carried out by the 3D full electromagnetic simulation program — the Computer Simulation Technology (CST) Studio Suite. The performance analysis of the designed converter was carried out according to the reflection coefficients in the frequency range of 4–21 GHz. It was fabricated using the traditional printed circuit board production method, and its performance was validated in microwave X-band by free-space microwave measurements. More information about the conversion mechanism of the converter was also provided by parametric study and surface current analysis. It is observed that the PC design, which has wide angular independence (50°), can be configured to be efficiently used in radar cross section (RCS) reduction and stealth applications.
AtıfScopus10WoS10OpenAlex8İncele - MakaleAçık Erişim2025Scopus SJRQ1Quantification of Honey Adulteration Using a Planar Microstrip Metamaterial-Motivated Sensor and Software-Defined Radio
Cem Hasar, Ugur; Hasar, Hafize; Kaya, Yunus; Ozturk, Hamdullah; Korkmaz, Huseyin; Kosunalp, Selahattin; Iliev, Teodor; Tariqul Islam, Mohammad; Nayyeri, Vahid; Mustafa Ramahi, Omar
This work presents the application of a planar microstrip metamaterial (MM)-motivated sensor in the form of a split-ring resonator (SRR) for the detection and quantification of water adulteration in honey samples. The proposed sensor utilizes inexpensive software-defined radio (SDR) measurements, offering a cost-effective solution. Unlike previous MM sensors employing SRR configuration, our proposed MM-motivated sensor is integrated with a microstrip feedline and an additional vertical bar, enhancing its sensing capability. To enable accurate measurements, a simple calibration procedure based on baseline normalization is implemented, allowing for amplitude-only transmission measurements (|S-21|) using the SDR. A special sample holder was designed to increase the repeatability of measurements. We separately employ two postprocessing techniques, namely, the rolling average (RA) approach and the Savitzky-Golay (SG) filter, to effectively eliminate ripples in the measured |S-21| data obtained from the SDR. For validation and evaluation of the proposed sensor and postprocessing techniques, measurements of flower honey samples with water adulteration levels (delta ) up to 10% (mass-to-mass basis) were also performed using a vector network analyzer (VNA). The resonance frequency of |S21| is utilized as the basis for analysis. We establish a metric function (linear function) that correlates the shift in resonance frequency with delta. It is observed that this function fits to measured resonance frequency values with an R(2 )value greater than 0.96 for both postprocessing techniques with or without the sample holder. By inverting this function, we can predict delta with considerable accuracy for a given resonance frequency by using another linear function. It is observed that percentage variations between predicted and measured delta values are between 1.54% and 6.46% for testing samples with delta = 5% and delta = 7%.
AtıfScopus5WoS2OpenAlex5İncele - MakaleYalnız künye2025Scopus SJRQ1Sensitive Microwave Sensor for Detection and Quantification of Water in Adulterated Honey
Hasar, Hafize; Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Hamdullah; Korkmaz, Huseyin; Yuzgulec, Kadir; Karaaslan, Muharrem; Ebrahimi, Amir; Nayyeri, Vahid; Ramahi, Omar M.
Honey is a rich source of sugar and is one of the indispensable ingredients in infant foods. Thus, it can be subjected to adulteration due to its cost. Measurement techniques such as liquid chromatography and near-infrared spectroscopy, used for detecting any adulteration, are expensive and need to be conducted by highly trained personnel for off-line analysis. Microwave measurements, as a fast, simple, and relatively inexpensive analysis, have recently shown great potential in detecting adulteration within honey samples. Nonetheless, sensor types used in such measurements are conventional. In this study, a reflection-type sensitive microwave sensor terminated by a metal back is proposed for the first time in the literature for the detection and quantification of water percentage ( delta ) level (mass-to-mass basis) within water-adulterated honey samples. When compared with other resonance-based microwave cavity sensors, thanks to its eight strips located at the centers of two closed circular loops, it demonstrates superior frequency selectivity and sensitivity ( S=5.13 %) validated by full-wave 3-D simulations performed by the CST Microwave Studio and equivalent circuit analysis carried out by the Advanced Design System (ADS) software. For example, for ethanol, the proposed sensor gives a frequency shift of more than 1 GHz in the X band. Resonance frequency shift and variation of the reflection coefficient amplitude ( |S11| ) are measured at X band to detect honey samples with up to 8% adulteration level. Three different honey samples (flower honey, highland honey, and thyme honey) were examined to test the performance and applicability of the proposed sensor.
AtıfScopus18WoS14OpenAlex17İncele - MakaleAçık Erişim2024Scopus SJRQ1De-Embedding Technique for Parameter Extraction of Biaxial Bianisotropic Metamaterial Slabs
Hasar, Ugur Cem; Kaya, Yunus; Korkmaz, Huseyin; Iliev, Teodor
Among material classes of isotropic, anisotropic, bi-isotropic, and bianisotropic, the latter class is 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 - 12.4GHz) 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 (ɛ 2 and μ3) illustrate a thickness-resonance behavior revealed by additional measurements of the Case B - MM structure with different lengths (7.675 mm, 9.21 mm, and 10.475 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 |3/Λ 1A| | is 14 times greater than | xi 0 / Λ 1A| | at 10.85 GHz where Λ 1A is one of the terms related to measured S-parameters for the Case A - MM structure, and |∗ | denotes the magnitude of the complex number ∗
AtıfScopus1WoS1OpenAlex1İncele - MakaleAçık Erişim2024Scopus SJRQ1Simpler Reference-Plane-Invariant Method for Permittivity Extraction of Medium- or Low-Loss Dielectric Samples Using One-Port Measurements
Cem Hasar, Ugur; Ali, Husain; Kaya, Yunus; Stoyanov, Ivaylo
A microwave method is devised to extract relative complex permittivity (ϵr) of medium- or low-loss dielectric samples. It is simpler, non-iterative, reference-plane-invariant (RPI), and applicable for one-port waveguide measurements with short-circuit termination only. Besides, since it uses short-circuit termination reflection-only measurements, it is free from Fabry-Pérot resonances. Permittivity measurements of polyvinyl chloride (PVC) and polypropylene (PP) are performed at X-band (8.2-12.4 GHz) to examine the performance of the proposed method considering different scenarios involving inaccurate information of sample location in the cell and inaccurate knowledge of the sample thickness. Repeatability analysis is carried out to analyze the performance of the proposed method against other similar methods in the literature.
AtıfScopus6WoS5İncele - MakaleAçık Erişim2024Scopus SJRQ1Simple and inexpensive microwave setup for industrial based applications: Quantification of flower honey adulteration as a case study
Hasar, Ugur C.; Hasar, Hafize; Ozturk, Hamdullah; Korkmaz, Huseyin; Kaya, Yunus; Ozkaya, Mehmet Akif; Ebrahimi, Amir; Barroso, Joaquim J.; Nayyeri, Vahid; Ramahi, Omar M.
A simple and inexpensive microwave measurement setup based on measurements of magnitudes of transmission properties ( | S 21 | dB \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}|S₂₁|_dB\end{document} ) is proposed for industrial-based microwave aquametry (moisture or water content) applications. An easy-to-apply calibration procedure based on normalization is implemented to eliminate systematic errors in the measurement system. As a case study, we applied this setup for the quantification of water-adulteration in flower honey. After validating this system by distilled water and pure flower honey measurements, | S 21 | dB \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}|S₂₁|_dB\end{document} measurements of the pure flower honey with various adulteration percentages ( delta \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}δ\end{document} ) up to 9% are conducted to examine the performance of the measurement setup for quantification of water adulteration. A multi-dimensional fitting procedure is implemented to predict delta \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}δ\end{document} using the proposed inexpensive microwave measurement setup. It is shown that it is possible to quantify an adulteration level with an accuracy better than -/+ 1 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}∓ 1\end{document} % by the proposed measurement setup and the applied multi-dimensional fitting procedure.
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İncele - MakaleAçık Erişim2023A Nested Square Shaped Metasurface-Based Broadband Linear Polarization Converter for Ku-Band Applications
Kaya, Yunus
This 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 emphasized
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İncele - MakaleYalnız künye2023Scopus SJRQ2Ultra-thin reflective multifunctional polarization converter with nested circular ring-shaped metasurface-based for C- and X-band applications
Kaya, Yunus
This article presents a single-layer, ultra-thin and multifunctional polarization converter (PC) design using metasurface. The PC, which is proposed as a single layer, consists of a metal metasurface on the front side of a easily accessible FR-4 material and a metal termination on the back surface. The suggested PC features linear polarization (LP) characteristic within a frequency ranges of 5.21- 5.41 GHz and 7.53- 8.08 GHz in C-band, also 10.59- 10.84 GHz in X-band under normal incidence. It indicates the conversion performance of linear polarization to circular polarization (LP-CP) that has the properties of left-handed circular polarization (LHCP) in frequency range of 5.74–7 GHz in C-band and right-handed circular polarization (RHCP) in frequency range of 8.63- 10.15 GHz in X-band. Besides, the suggested PC provides more than 90% polarization conversion ratio (PCR) value in case of normal incidence (0∘) and over 80% PCR value in case of oblique incidence up to 45∘. Again, the suggested PC offers the same CP feature in two frequency regions where CP conversion takes place under normal incidence for angle of incidence up to 60∘. A prototype of suggested PC was produced, measured, and a good match was found between the results simulated via a commercial electromagnetic (EM) simulation program. Finally, the performance of suggested design is compared with existing studies in literature with its high aspects. In this context, the suggested PC may be useful for C- and X-band applications due to its simple structure, ultra-thin and compactness, low-cost, and performance of LP and CP conversion under wide oblique angles.
AtıfScopus4WoS3OpenAlex3İncele - MakaleAçık Erişim2023Scopus SJRQ2Cheaper, Wide-Band, Ultra-Thin, and Multi-Purpose Single-Layer Metasurface Polarization Converter Design for C-, X-, and Ku-Band Applications
Kaya, Yunus
This 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 (Formula presented.) 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 (Formula presented.). 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.
AtıfScopus13WoS10OpenAlex15İncele - Kitap BölümüYalnız künye2023Metasurfaces
Kaya, Yunus
The purpose of this book chapter is to ensure an extensive and appropriate definition of MSs, to determine their outstanding features, and also to emphasize some of the advantages that may be gained by using them. A superior property of MSs is their low loss behavior in contrast to MMs. Therefore, MSs permit us to use the extraordinary properties of MMs such as refraction and reflection without incurring production complications and the losses related to MMs.
- MakaleYalnız künye2023Scopus SJRQ1Parameter extraction method for reflection-asymmetric bianisotropic metamaterial slabs using one-port measurements
Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Hamdullah; Ertugrul, Mehmet; Ramahi, Omar Mustafa
An 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.
AtıfScopus3WoS3OpenAlex5İncele - MakaleYalnız künye2023Scopus SJRQ1Honey-Water Content Analysis by Mixing Models Using a Self-Calibrating Microwave Method
Hasar, Hafize; Hasar, Ugur C.; Kaya, Yunus; Ozturk, Hamdullah; Izginli, Mucahit; Oztas, Taskin; Aslan, Nevzat; Ertugrul, Mehmet; Barroso, Joaquim J.; Ramahi, Omar M.
Microwave 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.
AtıfScopus18WoS16OpenAlex18İncele