Browsing by Author "Aydin, Elif"

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An Algorithm for Passive Rfid Based Location Estimation
(Ieee, 2014) Ozyurt, Erdem; Aydin, Elif; Yapici, A. Cagri; Department of Electrical & Electronics Engineering
In this study, an indoor localization system is developed for the mobile robots. The localization system consists of a passive RFID tag and a reader. The passive RFID tag is placed on the robot and reader antennas are spatially dispersed into the room. For the localization, Selective Adaptive Weighted Centroid Localization (SAWCL) algorithm is used. Performance of the localization system is evaluated for the different tags.
Citation - WoS: 1
Analysis of a Dual Frequency Circular Patch Antenna
(Electromagnetics Acad, 2012) Can, Sultan; Kapusuz, K. Yavuz; Aydin, Elif; Department of Electrical & Electronics Engineering
This study demonstrates resonant frequencies of several shorting pin loaded circular antennas, which are dual-frequency antennas. Dual-frequency operation is formed by using a shorting pin, which is connected between ground and the radiated part of the antenna. There are various studies, which are used to produce dual-frequency operation, and among those methods, a shorting pin is used to form dual frequency circular patch antennas since there are rare studies on this issue and size reduction is possible by inserting a pin to an antenna. This study is done to expand the studies in the literature about a shorting pin loaded circular patch antennas. The parameters that affect the resonant frequencies of the antenna are also evaluated. The thickness, permittivity and shorting pin positions are varied and the resonant frequencies are examined according to the change of these parameters. Frequency ratios are determined for each variation and the results are compared.
Analysis of the Parameters That Effects the Operating Frequencies and Bandwidth of a Cpw-Fed Patch Antenna
(Ieee, 2013) Dagdeviren, Birkan; Kapusuz, K. Yavuz; Can, Sultan; Aydin, Elif; Mathematics; Department of Electrical & Electronics Engineering
In this study, the analysis of the effect of antenna parameters to the operating frequency is performed in a coplanar waveguide fed patch antenna. The effect of the size and the substrate of the design dual frequency antenna to the operating frequency and bandwidth are also evaluated. Bandwidth of the upper and lower frequency is also investigated and results are demonstrated. The method to increase the bandwidth is also presented by using the chosen parameters.
Citation - WoS: 2
An Application of High-Power Electromagnetic Pulse: Forming of Sheet Metal Using Electromagnetic Waves
(Ieee, 2015) Inanan, Gokhan; Baranoglu, Besim; Aydin, Elif; Department of Electrical & Electronics Engineering; Manufacturing Engineering
In this study, the application of high velocity metal forming process by means of electromagnetic field is proposed. Electromagnetic Sheet Metal Forming (ESMF) is a process of forming sheet metal with very high speed (in milliseconds) without mechanical contact using the energy density of a pulsed magnetic field. In this process, deformation of the workpiece is driven by a transient electric current that is induced in a coil using a capacitor bank and discharge switch. This study presents some experiments and their results by examining the effects of different parameters in the proposed ESMF setup. The analysis and modelling of Electromagnetic sheet metal forming (ESMF) process is presented, as well. It has been seen that, it is possible to design a new system using the outcomes of this study.
A Bayes decision model for RSS based location estimation
(Ieee, 2007) Dincer, Zeynep; Oektem, Rwen; Aydin, Elif; Department of Electrical & Electronics Engineering
This work introduces a location estimation method based on Bayes Decision Theory using Radio Signal Strengths for indoor environment. Signal Strengths are observed through three transmitters at three distinct frequencies in UHF band, an active RFID tag and a modem connected to a computer. The test environment is 2100cmx720cm, which is divided into classed of square grids. For each class, a set of received signal strengths are measured and processed. Assuming that the class in which the RFID tag was located in the previous time of measurement is known, the next location (class) is estimated using Bayes Decision Theory. Proposed method is tested in a laboratory environment with obstacles. Results show that proposed method will be successful in location estimation where the estimation error stays within around 2m.
Citation - WoS: 1
Citation - Scopus: 3
Calculation of Resonant Frequencies of a Shorting Pin-Loaded Etma With Ann
(Wiley-blackwell, 2014) Can, Sultan; Kapusuz, Kamil Yavuz; Aydin, Elif; Department of Electrical & Electronics Engineering
[No Abstract Available]
Comparative Assessment and Performance Analysis of Interference Mitigation Techniques for Co-Existent Non-Geostationary and Geostationary Satellites
(Wiley, 2024) Ozturk, Faik; Aydin, Elif; Kara, Ali; Department of Electrical & Electronics Engineering
In recent years, technological developments with user demands, reduced production, and launch costs have rapidly increased the number of Low Earth Orbit (LEO) satellites in space. Since LEO satellites use the same frequency band as existing Geostationary Earth Orbit (GEO) satellites, the interference coordination between the two satellite networks is vital. In order to minimize the co-existent interference between these satellite networks, studies perform on different interference mitigation strategies. In this paper, analysis and comparative assessment of these interference mitigation techniques are presented for the co-existent Non-Geostationary Earth (NGEO) and GEO systems. More specifically, power control (PC) and spatial isolation-based link adaptation (SILA) techniques are studied comparatively for the performance evaluation. It is shown that the communication link bandwidth is more efficiently utilized in the SILA technique when compared with the PC technique. Moreover, the multi-objective optimization problem (MOP) approach in the SILA technique is demonstrated to be more effective when compared with the single-objective optimization problem (SOP) approach used in the PC technique as the simultaneous prioritizing objective functions outperforms single prioritization. Finally, it is shown that when the PC technique is applied together with the SILA technique, the exclusive angle (EA) can be reduced up to 8% for 100 Mbps, and 8.5% for 200 Mbps transmission bit rates in different operational scenarios. The presented performance evaluation in this paper may help the satellite operator or decision-maker gain insights on which mitigation technique can be used in the case of a co-existent interference. This paper proposes analysis and comparative assessment of interference mitigation techniques for the co-existent Non-Geostationary Earth (NGEO) and Geostationary Earth Orbit (GEO) systems. Spatial isolation-based link adaptation (SILA) and power control (PC) techniques are studied comparatively for the performance evaluation. The obtained optimization results show that the communication link bandwidth is more efficiently utilized in the SILA technique when compared with the PC technique because of the simultaneous prioritizing of objective functions. image
Citation - WoS: 6
Citation - Scopus: 9
Comparative Assessment of Electromagnetic Simulation Tools for Use in Microstrip Antenna Design: Experimental Demonstrations
(Wiley, 2019) Bilgin, Gulsima; Yilmaz, Vadi Su; Kara, Ali; Aydin, Elif; Electrical-Electronics Engineering; Department of Electrical & Electronics Engineering
This 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.
COMPARISON OF COMPUTER-BASED PROPAGATION MODELS WITH EXPERIMENTAL DATA COLLECTED IN AN URBAN AREA AT 1800 MHz
(Ieee, 2015) Acar, Tarik; Caliskan, Fatma; Aydin, Elif; Department of Electrical & Electronics Engineering
Nowadays a lot of models are set for the efficient and economic usage of frequency band since the band is a limited source. Therefore, the propagation models created for this purpose were studied in the literature. These models are Free Space Path Loss (Fspl) + Reflection plus Multiple Diffraction (RMD), COST-Hata and COST-WI models. In order to compare the success of the models, electric field strength measurements were taken in a chosen district (Mustafa Kemal Mahallesi Ankara, Turkey) where an irregular structure style can be observed. First set of measurements were recorded at random coordinates and second set of measurements were collected by the following coordinates tracking on a single line. As a conclusion, measured values were compared with the results which were taken from the mentioned models with graphical presentations. The most appropriate model was tried to be found and as another aim of the study, a correction factor was generated as a modification for COST-Hata propagation model.
Citation - WoS: 8
Citation - Scopus: 12
Computation and Optimization of Resonant Frequency and Input Impedance of a Coax-Fed Circular Patch Microstrip Antenna
(John Wiley & Sons inc, 2007) Gurel, Cigdem Seckin; Aydin, Elif; Yazgan, Erdem; Department of Electrical & Electronics Engineering
Microstrip antennas are important elements of today's wireless communication networks. In their various applications, it is critical to provide wide hand operation around the resonant frequency providing good impedance match between the antenna element and the feed. In this study, new, simple, arid accurate computation of resonant frequency and input impedance of double-layered, coaxial fed circular disk microstrip antenna with air gap is performed. In the analysis, new effective radius and permittivity expressions are used in simple and modified form including modal effects. Then, a new approach is proposed to provide input impedance matching (it resonant frequency via the application of microgenetic algorithm for wide hand operation. The accuracy of theoretical calculations and impedance matching approach are presented for various,structural parameters and operational modes of the antenna. (C) 2007 Wiley Periodicals, Inc.
Citation - WoS: 1
Design and Analysis of Rectangular Dielectric Rod Antennas
(Ieee, 2015) Demir, Mahmut; Ozkok, M. Aybars; Caliskan, Fatma; Aydin, Elif; Department of Electrical & Electronics Engineering
In this study, rectangular dielectric rod antennas with different dimensions and different shapes are designed and analyzed using HFSS simulation software. To analyze the effects of these changes, five different antennas are designed and antenna gains and return loss values are compared.
Design and Fabrication of Dual-Frequency H-Shaped Antenna
(Ieee, 2013) Dagdeviren, Birkan; Kapusuz, K. Yavuz; Can, Sultan; Aydin, Elif; Department of Electrical & Electronics Engineering
In this study, the parameters that effects the operating frequency of dual frequency H-shaped antenna are examined. These parameters are determined as type of the dielectric constant of substrate, substrate thickness, dimensions of the antenna and dimensions of the slots that are used to obtain shape of H. The produced and simulated results of the proposed antennas are presented and compared with the studies in literature.
Design Considerations for Near To the Ground Communication System and Associated Sub-Ghz Low Profile Antenna
(Ieee, 2017) Yilmaz, Vadi Su; Bilgin, Gulsima; Aydin, Elif; Kara, Ali; Department of Electrical & Electronics Engineering; Electrical-Electronics Engineering
This paper presents propagation aspects of a peer-to peer communication link where antennas are placed near to the ground ( low height). First, some of the propagation models are evaluated for understanding of propagation mechanisms. In this regard, as the height of the antennas are very low and the distance is large enough, reflecting angle becomes very small that makes use of two ray model. On the other hand, in the horizontal plane, the positions of the scattering objects, as a source of lateral waves, might vary largely due to the terrain undulations along with variety of objects around the link. This makes propagation mechanisms a little bit complicated. In order to design low profile, high gain sub-GHz antenna for such propagation environment, microstrip antenna with vertical ground was designed and fabricated. The antenna is required to be protected from natural and man-made effects. Therefore, the antenna with associated sensors are embedded into a metal box with a dielectric cover. All these are discussed and some of the findings are presented.
Citation - WoS: 2
Citation - Scopus: 3
Design Considerations for Sub-Ghz Multilayer Microstrip Antenna for Near Ground Communication Links in Rural Areas
(Ieee, 2017) Bilgin, Gulsima; Yilmaz, Vadi Su; Aydin, Elif; Kara, Ali; Department of Electrical & Electronics Engineering; Electrical-Electronics Engineering; Department of Electrical & Electronics Engineering; Electrical-Electronics Engineering
This paper presents some preliminary results of design and development of sub-GHz multilayer microstip antenna for use in near ground communication applications. In design stage of the antenna, iterative approach was applied. Firstly, a two layer microstrip antenna design process is presented. Next, the corners of the patch were cut, and a vertical wall on all sides of the antenna were introduced. In this way, both the size and resonant freqeuncy can be tuned. Moreover, as an application specific requirement, it is intended to embed this antenna into a metal box in order to protect it from man-made and natural environmental effects. This was also studied, and effects of the embedding ground on the antenna characteristics were examined. It is shown that the designed antenna provides -27dB resturn loss, and 7.3dB peak gain at 915MHz with the dimension of 150x200x13mm. Some preliminary measurements have proven the simulations.
Citation - WoS: 4
Dual-Frequency, Two Shorting Pin-Loaded Equilateral Triangular Patch Antennas
(Electromagnetics Acad, 2012) Can, Sultan; Kapusuz, K. Yavuz; Aydin, Elif; Basic Sciences; Nutrition and Dietetics; Department of Electrical & Electronics Engineering
This study presents the resonant frequencies of several antennas, which are dual-frequency antennas. These antennas possess two shorting pins to form dual frequency. Among several methods to provide dual operation, two shorting pins are used to form dual frequency equilateral triangular antennas since there are limited studies on this issue and higher frequency ratios are achievable. The present study has been done with this in mind in order to contribute to related literature on such antennas. Here, the parameters that affect the resonant frequencies of the antenna are also evaluated. The thickness, side length, and shorting pin positions are changed numerous times, and the resonant frequencies are examined according to the change of these parameters. Finally, the frequency ratios are determined for each variation, and the results are compared. The proposed antennas in present study achieved a frequency ratio around 5.7, which is significantly higher from the ones presented in the literature.
How To Teach Usage of Equipments in a Remote Laboratory
(IEEE, 2007) Alparslan, N. Ceren; Cagiltay, Nergiz Ercil; Ozen, Mustafa; Aydin, Elif; Department of Electrical & Electronics Engineering; Software Engineering
European Remote Radio Laboratory (ERRL) is an e-learning project for students, teachers and technicians of the universities who will use the very important devices of this laboratory remotely. These devices are very expensive to buy and can be broken easily while they have been using by the people who does not really know how to use them professionally. As a solution we have developed an e-leaming system which aims to support the ERRL learners while studying on how to use equipments in the system. The system is developed according to the electronic performance support systems (EPSS) approach. An EPSS is a computer-based, well-structured system which improves the performance of individuals. It is an electronic infrastructure that contains, stores and distributes personal (individual) or corporate knowledge to enable people to reach necessary levels of performance in the fastest possible time and with minimum teaching support of other people. This paper discusses how the content for such a system is developed and how this content is interactively used in the EPSS platform. The technical details of the developed EPSS are also discussed in this study. We believe that this paper will help instructional system designers for designing different alternatives to improve learners' performance.
Citation - WoS: 7
Citation - Scopus: 8
Implementing Consecutive Project-Based Learning in an Antenna and Propagation Course
(Sage Publications Ltd, 2016) Aydin, Elif; Kalayci, Elif; Department of Business; Department of Electrical & Electronics Engineering
In this study, a 'consecutive-project-based learning' structure applied to the antennas and propagation course is introduced. The first project, carried out with the faculty of management, aims to familiarize the teams with the challenges of 'real life tender-like conditions'. In the following three projects, teams perform their assigned antenna projects. Each team researches the theoretical background, studies the main parameters of antennas and evaluates them. After designing, simulating, specifying the testing requirements of the antennas, each team makes one financial and one time budget. At the end of the term, each team makes a presentation to a jury. Finally, a questionnaire is conducted to evaluate the achievement of the outcomes. This paper focuses on the first two projects because they constitute the critical stages of the course as the first project enables inexperienced students to discover the issues they might face in a 'real world' project and draw lessons from that experience to be used in the more comprehensive following project. The first project's aim is to equip the inexperienced students with elementary knowledge on working in a team; paying attention to time, budget, project phases and people management issues so that they can use that knowledge in the second project, thus learning takes place as a product of consecutive projects. Statistical information on the students' academic performances is analyzed to observe if this course has improved their academic performance. The results indicate that 'consecutive-project-based learning' is an effective method in antennas and propagation course.
An Indoor Navigation Aid Designed for Visually Impaired People
(Ieee, 2008) Oktem, Rusen; Aydin, Elif; Cagiltay, Nergiz Ercil; Department of Electrical & Electronics Engineering; Software Engineering
This work introduces the hardware architecture and general principles of a portable indoor navigation system for guiding visually impaired people. It operates through wireless communication between a compact hardware interface unit carried by the user, a central processing unit and an active RFID unit. The RFID unit collects signals as regard to the position of the user, the central system processes those signals to estimate the position of the user and proposes a route and direction for the user to follow, whereas hardware interface unit provides interaction. The orienteering of the user is obtained by a tactile compass.
ISAR Imaging of Drone Swarms at 77 GHz
(Tubitak Scientific & Technological Research Council Turkey, 2025) Coruk, Remziye Busra; Kara, Ali; Aydin, Elif; Department of Electrical & Electronics Engineering
The proliferation of easily available, internet-purchased drones, coupled with the emergence of coordinated drone swarms, poses a significant security threat for airspace. Detecting these swarms is crucial to prevent potential accidents, criminal misuse, and airspace disruptions. This paper proposes a novel inverse synthetic aperture radar (ISAR) imaging technique for high-resolution reconstruction of drone swarms at 77 GHz millimeter wave (mmWave) frequency, offering a valuable tool for military and defense antidrone systems. The key parameters affecting down-range and cross-range resolution (0.05 m), ultimately enabling the generation of detailed ISAR images are discussed. Here, we create diverse scenarios encompassing various swarm formations, sizes, and payload configurations by employing ANSYS simulations. To enhance image quality, different window functions are evaluated, and the Hamming window is selected due to its highest peak signal-to-noise ratio (PSNR) (16.3645) and structural similarity (SSIM) (0.9067) values, ensuring superior noise reduction and structural preservation. The results demonstrate that the effectiveness of high-resolution ISAR imaging in accurately detecting and characterizing drone swarms pave the way for enhanced airspace security measures.
Citation - WoS: 1
Citation - Scopus: 3
Low Radar Cross Section Uav Design in X-Band
(Ieee, 2022) Unalir, Dizdar; Sezgin, Sila; Yuva, Cansu Sena; Yalcinkaya Gokdogan, Bengisu; Aydin, Elif; Department of Electrical & Electronics Engineering; Electrical-Electronics Engineering
As Unmanned Aerial Vehicles (UAVs) have become widespread in defense industry, the radar technology that can detect them has also improved. These improvements cause UAVs to be detected more easily, which limits their effectiveness in military usage. Although the reduction of the radar cross-section (RCS) can provide a solution to this issue, the studies regarding that is insufficient in the literature. In this study, a shaping method is recommended to reduce the RCS of UAVs, and it is shown the method is effective to address the problem. Firstly, using a simulation tool, an UAV model is designed from simple shapes and the model is validated by comparing it with the ones in literature. Secondly, RCS values are measured using vertical and horizontal polarization throughout 360 degrees by incrementing the aspect angle by one degree in X-Band using the CST Studio Suite environment. Then, considering the hardware and aerodynamic requirements as well as limitations of the UAV model, a shaping technique is applied to the body, legs and the hollow parts of the UAV model with parametric simulations. The results show that the recommended shaping technique can provide a significant reduction in the RCS of an UAV.