Yazar "Unal, Ilhami" seçeneğine göre listele

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    Comparison of Free Space Measurement Using a Vector Network Analyzer and Low-Cost-Type THz-TDS Measurement Methods Between 75 and 325 GHz
    (Springer, 2017) Ozturk, Turgut; Morikawa, Osamu; Unal, Ilhami; Uluer, Ihsan
    Specifications of two measurement systems, free space measurement using a vector network analyzer and low-cost-type terahertz time-domain spectroscopy using a multimode laser diode, have been compared in the frequency region of millimeter/sub-THz waves. In the comparison, accuracy, cost, measurement time, calculation time, etc. were considered. Four samples (Rexolite, RO3003, Ultralam 3850HT-design, and L1000HF) were selected for the comparison of the specifications of the two methods. The acquired data was used to compute the complex permittivity of measured materials. The extracted results by free space measurement agreed well to the ones obtained by low-cost-type terahertz time-domain spectroscopy. This result proves free space measurement that can be assessed as a new method of material characterization in the sub-THz region successfully worked. Furthermore, free space measurement was proved to be suitable for a measurement in a narrow frequency range. On the other hand, low-cost-type terahertz time-domain spectroscopy has features not only low cost but also measurement capability in wide frequency range.
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    Experimental Studies Based on Classification of Explosive and Non-Explosive Liquids
    (Ieee, 2017) Ozturk, Turgut; Sayiniti, Aysun; Unal, Ilhami
    Nowadays, since the explosive liquids can easily be obtained by mixing simple substances, the electromagnetic methods developed for safety purposes have gained acceleration. In this study; liquids which may be explosive with chemical explosion, combustion and combination, as well as, non-explosive liquids which may be found inside baggages in airports are used to measure electromagnetic responses ranging from 1-50 GHz and complex dielectric permeability coefficients are calculated with commercial software. Explosive and non-explosive liquids are classified a with the help of three different algorithms such as PLS, PCA and K-Means.
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    Extracting the dielectric constant of materials using ABC-based ANNs and NRW algorithms
    (Taylor & Francis Ltd, 2016) Ozturk, Turgut; Elhawil, Amna; Dugenci, Muharrem; Unal, Ilhami; Uluer, Ihsan
    Five different Nicolson-Ross-Weir (NRW) extracting techniques are used to extract the dielectric constants of Teflon, Rexolite, Glass (borosilicate and soda-lime), Paper, and Ultralam 3850HT from S-parameters. The results of these extraction techniques are used to train the Artificial Neural Networks. In order to improve the accuracy of the results, the weights of ANNs are calculated using artificial bee colony estimation method. The results are compared with that obtained using NRW, Newton-Raphson, and genetic algorithm. The obtained results indicate that the proposed model gives good extracted parameters as compared with the previously published results.
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    Materials classification by partial least squares using S-parameters
    (Springer, 2016) Ozturk, Turgut; Uluer, Ihsan; Unal, Ilhami
    This paper presents a simple and usable algorithm, which is called Partial Least Squares, to classify the samples in different thicknesses and frequency range. This model employed to reconstruct the samples using S-parameters which are collected by Vector Network Analyzer in Free Space Measurement method. The relationship of between S-parameters is showed to classify the materials using proposed model. The Partial Least Squares algorithm has a good potential to classify the different samples with non-contactless and non-destructive measurement method. The classification process will be easy by using the proposed model, due to its practical and simple usage. In addition, the extraction techniques, which are Nicolson Ross Weir, Newton-Raphson, and Genetic Algorithm, are used in order to extract the dielectric constant of samples, in this study. The Newton-Raphson algorithm is selected to obtain the complex permittivity of samples since it gives best results than other extracting techniques and the results are used for classification.
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    Materials classification by partial least squares using S-parameters (vol 27, pg 12701, 2016)
    (Springer, 2019) Ozturk, Turgut; Uluer, Ihsan; Unal, Ilhami
    The original version of this article unfortunately published incorrectly in the definition of complex permittivity extraction given in the relation (5) of [1] due to its minus sign.
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    Permittivity Measurements for Dielectric Lens and Dielectric Rod Antenna Designs
    (Ieee, 2016) Panin, Sergey B.; Unal, Ilhami; Sayinti, Aysun; Ozturk, Turgut; Tekbas, Mustafa
    For dielectric materials being often utilized in quasi-optical components, the permittivity was evaluated by free-space method in W-band. The obtained permittivity value was applied to designing of low aberration large aperture aspheric dielectric lens and dielectric waveguide rod antenna. These components composed the antenna system for the passive radiometric imaging in 90-100 GHz frequency range. This antenna system was experimentally demonstrated to successfully detect and recognize the metallic weapon hidden under outer clothing.
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    Reduction of S-parameter errors using singular spectrum analysis
    (Amer Inst Physics, 2016) Ozturk, Turgut; Uluer, Ihsan; Unal, Ilhami
    A free space measurement method, which consists of two horn antennas, a network analyzer, two frequency extenders, and a sample holder, is used to measure transmission (S-21) coefficients in 75-110 GHz (W-Band) frequency range. Singular spectrum analysis method is presented to eliminate the error and noise of raw S-21 data after calibration and measurement processes. The proposed model can be applied easily to remove the repeated calibration process for each sample measurement. Hence, smooth, reliable, and accurate data are obtained to determine the dielectric properties of materials. In addition, the dielectric constant of materials (paper, polyvinylchloride-PVC, Ultralam (R) 3850HT, and glass) is calculated by thin sheet approximation and Newton-Raphson extracting techniques using a filtered S-21 transmission parameter. Published by AIP Publishing.