Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Kaya, Yunus(6)
- Hasar, Ugur C.(3)
- Ali, Husain(2)
- Hasar, Ugur Cem(2)
- Korkmaz, Huseyin(2)
- Ozturk, Gokhan(2)
- Ozturk, Hamdullah(2)
- Barroso, J.J.(1)
- Bute, M.(1)
- Cem Hasar, Ugur(1)
- Ebrahimi, Amir(1)
- Ertugrul, M.(1)
- Ertugrul, Mehmet(1)
- Hasar, Hafize(1)
- Hasar, U.C.(1)
- Iliev, Teodor(1)
- Karaaslan, Muharrem(1)
- Kaya, Y.(1)
- Nayyeri, Vahid(1)
- Ramahi, Omar M.(1)
- Stoyanov, Ivaylo(1)
- Xue, Bing(1)
- Yuzgulec, Kadir(1)
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 - 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 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 - 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 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 Erişim2022Scopus SJRQ1Calibration-Free Time-Domain Free-Space Permittivity Extraction Technique
Hasar, Ugur C.; Ozturk, Gokhan; Kaya, Yunus; Ertugrul, Mehmet
A time-domain free-space technique has been proposed to extract relative permittivity ( _r ) and effective conductivity ( σ _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 _r and σ _e of polyethylene and polypropylene low-loss samples.
AtıfScopus29WoS28OpenAlex29İncele - MakaleYalnız künye2014Scopus SJRQ2Simple procedure for robust and accurate complex permittivity measurements of low-loss materials over a broad frequency band
Hasar, U.C.; Barroso, J.J.; Kaya, Y.; Bute, M.; Ertugrul, M.
In this research paper, we propose a simple procedure for accurate, stable and broadband measurements of complex permittivity of low-loss dielectric samples with considerable lengths. We identify and demonstrate by numerical and analytical analyses the main ill-behaved factor that gives rise to inaccurate peaks for measurements of electrical properties of low-loss samples in the well-known Nicolson-Ross-Weir method. Without using this factor in the expressions and combining better features of the methods available in the literature, the proposed procedure allows highly accurate permittivity measurements over a broad band. We have validated the proposed method by permittivity measurements of a low-loss sample by different methods.
AtıfScopus4WoS4OpenAlex3İncele