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Article Citation - WoS: 11Citation - Scopus: 15A Study on the Performance Evaluation of Wavelet Decomposition in Transient-Based Radio Frequency Fingerprinting of Bluetooth Devices(Wiley, 2022) Almashaqbeh, Hemam; Dalveren, Yaser; Kara, AliRadio frequency fingerprinting (RFF) is used as a physical-layer security method to provide security in wireless networks. Basically, it exploits the distinctive features (fingerprints) extracted from the physical waveforms emitted from radio devices in the network. One of the major challenges in RFF is to create robust features forming the fingerprints of radio devices. Here, dual-tree complex wavelet transform (DT-CWT) provides an accurate way of extracting those robust features. However, its performance on the RFF of Bluetooth transients which fall into narrowband signaling has not been reported yet. Therefore, this study examines the performance of DT-CWT features on the use of transient-based RFF of Bluetooth devices. Initially, experimentally collected Bluetooth transients from different smartphones are decomposed by DT-CWT. Then, the characteristics and statistics of the wavelet domain signal are exploited to create robust features. Next, the support vector machine (SVM) is used to classify the smartphones. The classification accuracy is demonstrated by varying channel signal-to-noise ratio (SNR) and the size of transient duration. Results show that reasonable accuracy can be achieved (lower bound of 88%) even with short transient duration (1024 samples) at low SNRs (0-5 dB).Article Citation - WoS: 6Citation - Scopus: 9Comparative Assessment of Electromagnetic Simulation Tools for Use in Microstrip Antenna Design: Experimental Demonstrations(Wiley, 2019) Bilgin, Gulsima; Yilmaz, Vadi Su; Kara, Ali; Aydin, ElifThis paper presents a better understanding of the use of finite integration techniques (FIT) and finite element method (FEM) in different types of microstrip antennas in order to determine which numerical method gives relatively more accurate results. Although the theoretical formulation based on Maxwell's equations of both FEM and FIT are approached from different aspects in the literature, there is still a lack of comparison of the same antenna type using different numerical methods employing FEM and FIT. Therefore, in this study, FEM and FIT were applied to two different types of microstrip antennas, and their simulation and experimental results was compared. For the first antenna demonstration, a multilayer structure was chosen to achieve one of the significant parameters. Then, a microstrip antenna with a compact structure was used in the second demonstration. Using these two antennas, the accuracy of FEM and FIT in different structures were compared and all simulated return loss and gain results were verified by the measured results. The experimental demonstrations show that FEM performs better for both types of microstrip antennas while FIT provides an adequate result for two-layer microstrip antennas.Article A Case Study on the Assessment of Rf Switch and Splitter Options for Coupling of Transceiver Modules To Bidirectional Antennas Employed in Linear Wireless Sensor Networks(Wiley, 2021) Dalveren, Yaser; Durukan, Ahmet Mert; Kara, AliRecently, a concept of linear wireless sensor networks (LWSNs) has attracted much attention. For such networks, one of the key challenges in sensor node design is to couple transceiver modules with bidirectional antennas placed back-to-back for opposite radiation. As is known, simply, this can be achieved by using well-known coupling options like radio frequency (RF) switch or splitter. However, it is important to decide between two seemingly equally good options according to the system requirements such as RF performance, power consumption, and cost. Therefore, this study aims to comparatively assess these options from the system level point of view to find out what advantages or disadvantages either provides as per the other from widespread use of them in a LWSN-based cathodic protection monitoring of oil and natural gas pipelines in extreme environments. Preliminary field tests are also conducted to validate the efficiency of coupling options for LWSN links. Results show that RF splitter offers low power consumption and cost whereas RF switch has advantages of low loss. Thus, it is believed that this study may provide useful insights to design bidirectional sensor links for LWSNs.Article Citation - WoS: 8Citation - Scopus: 10Thickness Effects on the Dielectric Dispersion and Optical Conductivity Parameters of Cuo Thin Films(Wiley, 2020) Qasrawi, Atef F.; Qasrawı, Atef Fayez Hasan; Hamamdah, Alaa A.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringIn this article, the effect of film thickness on the structural, optical, dielectric, and optical conductivity parameters of CuO thin films are reported. CuO thin films which are prepared by the physical vapor deposition technique under vacuum pressure of 10(-5) mbar with various thicknesses in the range of 50 to 1000 nm are observed to exhibit amorphous nature of growth. The values of the energy bands gaps, the spectral response of the dielectric constant and of the optical conductivity parameters are highly sensitive to the film thickness. Particularly, while the 50 nm thick CuO films exhibits quantum confinement which forces the material to have wide band gap (2.70 eV), the thicker films display an energy band gap in the infrared range of spectrum. It was also observed that the thicker the films, the more pronounced the nonlinear dielectric response. In addition, analysis of the optical conductivity parameters using Drude-Lorentz approach for optical conduction has shown that the 50 nm thick films can display drift mobility value of 4.65 cm(2)/Vs accompanied with plasmon frequency of 1.20 GHz and free carrier density of 7.5x10(17) cm(3). The Drude-Lorentz analysis has also shown that the free carrier density and the plasmon frequency of CuO decreases with increasing film thickness. This decrement is accompanied with enhancement in the drift mobility values which reaches 12.56 cm(2)/V s as the film thickness exceeds 250 nm. Such features of the thin layer of CuO make them suitable for the production of nano/microthin film transistors.Article Citation - WoS: 3Citation - Scopus: 3Hot aluminum substrate induced hexagonal-tetragonal phase transitions in InSe and performance of Al/InSe/Cu2O pn tunneling devices(Wiley, 2020) Qasrawi, Atef Fayez; Kmail, Reham RedaIn the current study, we have considered the induced phase transitions in Al/InSe thin film substrates and employing them for fabrication of InSe/Cu2O tunneling channels. The InSe substrates are observed to prefer the transition from the hexagonal gamma-In(2)Se(3)to the rarely observed tetragonal InSe. The phase transitions are obtained by the thermally assisted diffusion of aluminum, which was already kept at 250 degrees C in a vacuum media of 10(-5)mbar before the compensation of InSe. The tetragonal InSe also induced the crystallization of orthorhombic Cu2O with acceptable level of lattice matching along thea-axis. The Al/InSe/Cu2O/Au heterojunctions, which are electrically analyzed are observed to exhibit rectifying features with the current conduction being dominated by electric fields assisted thermionic emission (tunneling) through a barrier of width of 5.5 to 14.0 nm and barrier height of 0.19 to 0.30 eV. The ac analyses of the capacitance and conductance spectra of this device have shown that it can exhibit high/low capacitance and frequency dependent conductance switching modes at 0.12 GHz in addition to negative capacitance effect in the range of 0.12 to 1.80 GHz. The features of the device are promising as they indicate the suitability of the device for fabrication of field effect transistors, memory devices, and ultrafast switches.Article Citation - WoS: 5Citation - Scopus: 5Structural and Electrical Characterizations of the as Grown and Annealed Au/Mοo3< Bandpass Filters(Wiley, 2019) Khanfar, Hazem K.; Qasrawi, Atef; Daraghmeh, Masa; Abusaa, MuayadIn this work, the structural, morphology, and electrical properties of two 500 nm thick molybdenum trioxide layers that are sandwiched with indium slab of thickness of 200 nm (MoO3/In/MoO3 [MIM]) to form a bandpass filter are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and impedance spectroscopy techniques, respectively. The MIM films which coated onto Au thin film substrates by the thermal evaporation technique under vacuum pressure of 10(-5) mbar was post annealed at 250 degrees C in air atmosphere. While the XRD analysis revealed polycrystalline hexagonal lattice structure of the Au/MLM samples, the SEM and EDS analysis displayed grains of sizes of 350 nm and stoichiometric structure of MoO3. Electrically, indium layer which caused n-type conduction with donor level of 299 meV, forced the material to exhibit negative capacitance (NC) effect at high frequencies (above 1.1 GHz). The impedance spectroscopy which was recorded in the frequency domain of 0.01 to 1.80 GHz, also revealed low pass and high pass filters characteristics in the low and high frequency domains, respectively. The annealing of the Au/MIM samples, decreased the crystallite and grain sizes and increased the microstrain, the defect density and the stacking faults. Small amount of excess oxygen and some indium deficiency are observed upon annealing. In addition, the annealing shifted the donor level closer to the bottom of the conduction band and inverted the NC effect from high to low frequency regions. The study indicates the applicability of the Au/MIM/C structures as microwave cavities and parasitic capacitance cancellers in electronic circuits.Article Citation - WoS: 4Citation - Scopus: 5Neural Network Based Resonant Frequency Solver for Rectangular-Shaped Shorting Pin-Loaded Antennas(Wiley, 2013) Can, Sultan; Kapusuz, Kamil Yavuz; Aydin, ElifThis study presents an artificial neural network (ANN) estimation of the operating frequencies of shorting pin-loaded rectangular microstrip patch antennas. A feed forward back propagation multilayer perceptron neural network structure is applied in the study. The results are compared with the ones in the literature and the FEM based simulation results. The results of the operating frequencies obtained by using this method are in very good agreement with the experimental results presented in the literature. Several antennas are also simulated by a finite element method based solver and these results are also compared with the results of the proposed neural network model. The average error of the lower frequency obtained by this study has a decrement of 2.025% when compared to the FEM based simulation software and for the upper frequency this difference is 6.835%. The effects of permittivity of the antenna, size of the dimensions of the rectangular patch, and the shorting pin position are also evaluated. In the light of the ANN model and the relations obtained two antennas in the same shape are produced and the results of these antennas are presented as well. (c) 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:3025-3028, 2013Article Citation - WoS: 40Citation - Scopus: 44Surface Characterization and Radical Decay Studies of Oxygen Plasma-Treated Pmma Films(Wiley, 2013) Ozgen, Ozge; Aksoy, Eda Ayse; Hasirci, Vasif; Hasirci, NesrinPolymethylmethacrylate (PMMA) films were modified by RF oxygen plasma with various powers applied for different periods, and the effects of these parameters on the surface properties such as hydrophilicity, surface free energy (SFE), chemistry, and topography were investigated by water contact angle, goniometer, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy, and the types of the created free radicals and their decay were detected by electron spin resonance spectroscopy (ESR). SFE and contact angle results varied depending on the plasma parameters. Oxygen plasma treatment (100 W-30 min) enhanced the hydrophilicity of PMMA surface as shown by decreasing the water contact angle from 70 degrees to 26 degrees. XPS analysis showed the change in the amounts of the present functionalities as well as formation of new groups as free carbonyl and carbonate groups. The roughness of the surface increased considerably from similar to 2 nm to similar to 75 nm after 100 W-30 min oxygen plasma treatment. ESR analysis indicated the introduction of peroxy radicals by oxygen plasma treatment, and the intensity of the radicals increased with increasing the applied power. Significant decrease in radical concentration was observed especially for the samples treated with higher powers when the samples were kept under the atmospheric conditions. As a conclusion, RF plasma, causes changes in the chemical and physical properties of the materials depending on the applied parameters, and can be used for the creation of specific groups or radicals to link or immobilize active molecules onto the surface of a material. Copyright (C) 2012 John Wiley & Sons, Ltd.Article Citation - WoS: 1Citation - Scopus: 1Tungsten Doped Bi1.5zn0.92< Ceramics Designed as Radio/Microwave Band Pass/Reject Filters(Wiley, 2021) Qasrawi, Atef F.; Abdalghafour, Mays A.; Mergen, A.Herein, radiowave/microwave bandpass/reject filters are fabricated from the tungsten doped Bi1.5Zn0.92Nb1.5-6x/5WxO6.92 (W-BZN) pyrochlore ceramics. The W-BZN band filters are prepared by the solid state reaction technique and subjected to X-ray diffraction (XRD) and impedance spectroscopy analyses. It was shown that the W-BZN filters can display negative capacitance effects accompanied with resonance-antiresonance oscillations. The calculations of the reflection coefficient parameter (S-11), the return loss (L-r) and the voltage standing wave ratios (VSWR) in the frequency domain of 0.01 to 1.80 GHz, has shown that the W-BZN device can perform as microwave cavities at two notch frequency values of 0.44 and 1.53 GHz. W-BZN devices can also be nominated as noise reducers and radiowave/microwave signal receivers suitable for telecommunication technology.Article Citation - WoS: 3Citation - Scopus: 3Enhancement of the Performance of the Cu2se Band Filters Via Yb Nanosandwiching(Wiley, 2019) Khusayfan, Najla M.; Qasrawı, Atef Fayez Hasan; Qasrawi, A. F.; Khanfar, Hazem K.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringIn this article, we report the experimental and theoretical modeling on the band pass filters that are made of two thin film layers of Cu2Se coated onto aluminum substrates and nanosandwiched with 50 nm ytterbium layers. The nanosandwiching of Yb between two layers of Cu2Se is found to decrease the lattice constant, the defect density, and the strain and increase the grain size in the Cu2Se. Electrically, it is observed that, Al/Cu2Se/Al structure exhibits wave trap characteristics with notch frequency of 1.31 GHz. The Yb-layers improved the performance of the band pass filters by increasing the amplitude of the reflection coefficients, increasing the return loss values and decreasing the voltage standing wave ratios. The calculated conduction and wave trapping parameters nominate the Yb-nanosandwiched Cu2Se films for use in communication technology as they exhibit negative capacitance effect and narrow band pass range.
