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Öğe A compact hairpin filter with stepped hairpin defected ground structure(Institute of Electrical and Electronics Engineers Inc., 2018) Sajjad, Hassan; Altaf, Ahsan; Khan, Sana; Jan, LatifA compact hairpin line bandpass filter is presented with two different defected ground structures (DGS). The DGS are used to reduce the distributive response of the microstrip filter. The harmonic at 2 fo is suppressed to below -20 dB. The filter has an insertion loss (IL) greater than -3 dB and return loss (RL) of 26 dB at the center frequency, 2.4 GHz. The designed filter has a sharp roll-off and a wide band of operation. The filter is fabricated using RO4350 substrate and measured results are compared with the simulations.Öğe Analysis of a compact multi-band textile antenna for WBAN and WLAN applications(Istanbul Technical University, 2021) Savcı, Hüseyin Şerif; Sajjad, Hassan; Kaburcuk, Fatih; Khan, SanaA dual-band wearable antenna is designed on a textile material. The design operates at ISM bands available for Wireless Body Area Network (WBAN) and Wireless Local Area Network (WLAN) with an input match better than -15 dB. The antenna is designed by using Computational Electromagnetic Software (CEMS) based on Finite-Difference Time-Domain (FDTD) method. A three-layer phantom model including skin, fat and muscle has been considered to compute the specific absorption rate (SAR). The maximum value of SAR averaged over 1g and 10g of tissue is less than 1.6 W/Kg and 2 W/Kg, respectively, when the maximum incident power of the antenna is 63 mW. These values are incompliance with the international electromagnetic safety standards.Öğe Compact dual-band implantable antenna for e-health monitoring(Institute of Electrical and Electronics Engineers, 2017) Sajjad, Hassan; Sethi, Waleed Tariq; Khan, Sana; Jan, LatifThis work presents a compact dual-band Planar Inverted F-antenna (PIFA) antenna useful for E-health monitoring and wireless sensors systems. The antenna operates in the Industrial Standard and Medical (ISM) and Wireless Medical Telemetry Service (WMTS) bands. It offers a compact size with dimensions 12.6 × 8.5 × 2.4 mm3. Two different simulators have been used to verify the results. The proposed antenna performs well in the presence of a bio-compatible insulator (BCI) material.Öğe ISM band 1:16 wilkinson power divider(Institute of Electrical and Electronics Engineers Inc., 2018) Altaf, Ahsan; Sajjad, Hassan; Khan, Sana; Munir, MehreA 1:16 Wilkinson power divider (WPD) working from 1.3 GHz to 3 GHz is presented in this paper. Equal power division, phase and amplitude consistency is achieved among the output ports. The proposed design has a wideband with a 10 dB fractional bandwidth of 76%. The isolation loss within the bandwidth is better than 15 dB and the insertion loss is less than 2 dB. The size of the WPD has been minimized to 16×10,7 cm 2, which was the main objective of this work. The compact size of the proposed design makes it a suitable candidate for feeding phased antenna arrays for wideband operations.Öğe Microwave heating of heavy oil and bitumen(Institute of Electrical and Electronics Engineers Inc., 2016) Arvas, Serhend; Sajjad, Hassan; Altaf, Ahsan; Khan, Sana; Arvas, ErcümentA theoretical study is presented for the feasibility of a microwave heating device that will raise the temperature of heavy oil and bitumen reservoir. The device is enclosed in a radome which is surrounded by a perforated metal pipe. Outside the pipe is occupied by a mixture of heavy oil and calcite. Various dielectric properties are assumed for the radome and the calcite region. Analytical and numerical results are presented for the temperature rise around the pipe.Öğe Mutual coupling compensation in receiving antenna arrays(Institute of Electrical and Electronics Engineers Inc., 2020) Khan, Sana; Sajjad, Hassan; Özdemir, Mehmet Kemal; Arvas, ErcümentMutual coupling compensation in uniform linear and circular receiving antenna arrays of thin wire dipoles is presented. It was observed that the mutual impedance is independent of the incident angle and depends solely on the geometry of the array. By using only one measurement, decoupling matrix is computed and direction of arrival is estimated.Öğe Mutual coupling compensation in receiving antenna arrays(Applied Computational Electromagnetics Society (ACES), 2020) Khan, Sana; Sajjad, Hassan; Özdemir, Mehmet Kemal; Arvas, ErcümentMutual coupling compensation in uniform linear and circular receiving antenna arrays of thin wire dipoles is presented. It was observed that the mutual impedance is independent of the incident angle and depends solely on the geometry of the array. By using only one measurement, decoupling matrix is computed and direction of arrival is estimated.Öğe Mutual coupling compensation in receiving arrays and its implementation on software defined radios(Institute of Electrical and Electronics Engineers Inc., 2020) Khan, Sana; Sajjad, Hassan; Özdemir, Mehmet Kemal; Arvas, ErcümentMutual coupling is compensated in a four element uniform linear receiving array using software defined radios. Direction of arrival (DoA) is estimated in real-time for the array with spacing d=lambda/4. The decoupling matrix was measured using a VNA for only one incident angle. After compensation the error in DoA estimation was reduced to 5%. Comparing the DoA results with d=lambda/2 spaced Uniform Linear Array (ULA), 1.2% error was observed. Although, the experiment was performed indoors with a low SNR, the results show a substantial improvement in the estimated DoA after compensation.Öğe Mutual coupling compensation in receiving arrays and its implementation on software defined radios(Applied Computational Electromagnetics Society, 2020) Khan, Sana; Sajjad, Hassan; Özdemir, Mehmet Kemal; Arvas, ErcümentMutual coupling is compensated in a four element uniform linear receiving array using software defined radios. Direction of arrival (DoA) is estimated in real-time for the array with spacing d=lambda/4. The decoupling matrix was measured using a VNA for only one incident angle. After compensation the error in DoA estimation was reduced to 5%. Comparing the DoA results with d=lambda/2 spaced Uniform Linear Array (ULA), 1.2% error was observed. Although, the experiment was performed indoors with a low SNR, the results show a substantial improvement in the estimated DoA after compensation.Öğe Mutual coupling compensation in transmitting arrays of thin wire antennas(Applied Computational Electromagnetics Society (ACES), 2018) Khan, Sana; Sajjad, Hassan; Özdemir, Mehmet Kemal; Arvas, ErcümentThis paper presents a numerical technique for the compensation of mutual coupling in transmitting arrays of thin wire antennas. The Method of Moments is used to compute the scattering parameters of the array. Using these parameters and the original excitations, a set of new excitation values are computed. The new excitation values compensate the effect of the mutual coupling. Computed results are given for linear, circular, and 3-Dimensional arrays. Uniform and binomial excitations are studied. Results obtained are compared with other available data and very good agreement is observed.Öğe Mutual coupling reduction in array elements using EBG structures(Institute of Electrical and Electronics Engineers, 2017) Sajjad, Hassan; Khan, Sana; Arvas, ErcümentA 2D electromagnetic band gap (EBG) structure is designed on the ground plane of 1×2 rectangular patch antenna array to reduce the mutual coupling between the two elements and enhance the radiation pattern. An isolation of -41 dB has been achieved with the EBG structure relative to -20 dB without the EBG.Öğe Scattering by a chiral cylinder of arbitrary cross section above a dielectric half-space(Institute of Electrical and Electronics Engineers Inc., 2021) Sajjad, Hassan; Altaf, Ahsan; Özzaim, Cengiz; Arvas, ErcümentA simple numerical solution for electromagnetic scattering from a 2-D homogeneous chiral cylinder of arbitrary cross section placed above a dielectric half-space (DHS) is presented. A modified surface equivalence principle is used to obtain coupled electric field integral equations. For feasible application of method of moments, a perturbation method is used where a strip of finite width approximates the surface of the infinite half-space. The perturbed currents on the interface are expressed as a difference of the currents with the cylinder present and the exact solution (cylinder removed). The excitation vector now contains the reflected field from the DHS in addition to the incident field. Transverse magnetic (TM) and transverse electric (TE) excitations are treated. Computed results include perturbed currents on the dielectric interface and the scattered fields. Excellent agreement is observed for special cases available in the literature.Öğe Scattering from a chiral cylinder of arbitrary cross-section above a dielectric half-space(İstanbul Medipol Üniversitesi Fen Bilimleri Enstitüsü, 2021) Sajjad, Hassan; Arvas, Ercümend; Özzaim, CengizA simple numerical solution for electromagnetic scattering from a two dimensional (2-D) homogeneous chiral cylinder of arbitrary cross-section placed above a dielectric half-space is presented. The surface equivalence principle and the Method of Moments (MoM) are used to replace the cylinder and the dielectric half-space by unknown equivalent electric and magnetic surface currents. By satisfying the continuity of the electric field's tangential components at the surfaces, a set of electric field integral equations (EFIE) is obtained. Since the dielectric surface is of infinite extent, the conventional MoM cannot be applied directly. Therefore, a perturbation method is used where a strip of finite width approximates the surface of the half-space. Then, this approximate problem is solved numerically with the conventional MoM. Pulses are used as basis functions and Galerkin's method is used for testing. The excitation vector now contains the reflected field from the dielectric half-space in addition to the incident field. Both TM and TEexcitations are treated. Computed numerical results include equivalent currents on the chiral cylinder, perturbed currents on the interface, and the scattered fields for various geometries. Studying various parameters for the chiral material revealed that the extra degree of freedom, chirality admittance, can be used effectively in controlling the radar cross-section (RCS) of the scatterer. However, the scattered fields cannot be predicted by simple theory, hence the need for such a study. Results for some simple problems are presented as well to check the validity of the developed algorithm. Advantages and disadvantages of the proposed method are discussed towards the end.Öğe Scattering from chiral cylinders of arbitrary cross-sections above a ground plane(IEEE-Institute of Electrical and Electronics Engineers Inc, 2021) Altaf, Ahsan; Sajjad, Hassan; Özzaim, Cengiz; Arvas, ErcümentThe main purpose of this work is to solve the problem of electromagnetic scattering from a chiral cylinder of arbitrary cross-section above an infinite perfect electric conducting (PEC) plane. Using image theory, this problem is reduced to two chiral cylinders in free-space. Surface equivalence principle is used to obtain three different equivalent problems for this two-cylinder problem. Then, the method of moments is used to solve these equivalent problems numerically. It is known that the image of a chiral body through a ground plane is another chiral body with the same permittivity and permeability but opposite chirality. Using this property, the two-body problem in the moment method may be reduced to a one-body problem with a complicated moment matrix. Computed numerical results include scattered fields and equivalent surface currents on the cylinder.
