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Conference Object Citation - Scopus: 25Blockage/Shadowing and Polarization Measurements at 2.45ghz for Interference Evaluation Between Bluetooth and Ieee 802.11 Wlan(2001) Kara,A.; Bertoni,H.L.We present measurement results at 2.45 GHz to evaluate blockage shadowing and fading effects due to furniture and people next to terminals for short range indoor communication systems. The followings are the results: people crossing the link near to a terminal can cause fading up to 20dB which is more than furniture blockage measured of about 5-13dB depending on objects over the links, polarization coupling was also measured by using dual polarized antenna at receiving end, and coupling is higher for obstructed links, which suggests polarization diversity.Conference Object Pilot Remote Experiment in the Errl: Measurement of Scattering Parameters(2007) Özen,M.; Aydin,E.U.; Kara,A.A remote laboratory platform enables the learners to access physical instruments at distant location and to perform experiments remotely via the Internet. This paper focuses on a pilot remote laboratory experiment on measurement of scattering parameters (s parameters) by using vector network analyzer (VNA) in the ERRL (European Remote Radio Laboratory) platform. The results of the pilot experiment are presented, and discussed shortly. © 2007 IEEE.Conference Object Citation - Scopus: 20Design and Development of a Remote and Virtual Environment for Experimental Training in Electrical and Electronics Engineering(2010) Kara,A.; Aydin,E.; Ozbek,M.E.; Cagiltay,N.European Remote Radio Laboratory (ERRL) has been developed by the support of European Commission. It intends to provide remote access to high cost devices remotely, and perform experiments in radio frequency (RF), communications and microwave domains of Electrical ad Electronics Engineering. The system has been operational for two years, and been integrated into curriculum of some courses. In this work, the hardware and software structures of the system are presented. Then, experimental content and the motivations in the design of the system are discussed. ©2010 IEEE.Article Citation - Scopus: 11Modelling of Shadowing Loss Due To Huge Non-Polygonal Structures in Urban Radio Propagation(Electromagnetics Academy, 2008) Kara,A.; Yazgan,E.Ray tracing algorithms rely on two dimensional or three dimensional database. They use ray optical techniques referred to as the uniform theory of diffraction (UTD) using building database given as polygons. Building geometries can also be modelled as having non-planar geometries, and this would be important in modeling of shadowing loss due to curved structures in urban radio propagation. To demonstrate modelling of buildings as non-polygonal geometries, a particular building composition involving 3D cruved geometries is chosen, and shadowing loss for this building composition is studied via UTD ray tracing. Building structure considered in this study involves main canonical shapes of non-planar geometries including cone, cylinder and sphere. Single and multiple interaction of surface diffractions, effect of creeping waves are taken into consideration in the analysis. © 2008, Electromagnetics Academy.Conference Object Citation - Scopus: 2Measurement of Local Environmental Effects in Uwb Channels(2006) Vural,M.D.; Yildiz,M.; Kara,A.[No abstract available]Conference Object Citation - Scopus: 2Design and Fabrication of Ka Band Circular Horn Antenna;(2012) Danaci,S.; Gürtekin,E.; Özyurt,E.; Kara,A.In this paper, design and fabrication of a circular horn antenna is presented. The antenna is designed for experimental use at Ka band. The design process includes feeding structure for coaxial line and geometrical parameters of the antenna. The bandwidth of the antenna is measured as 2.25GHz, (S 11 ≤-10dB) which satisfies the requirements of targeted experimental study. A reference monopole is also designed for the measurements of antenna parameters. Antenna radiation pattern is measured with the reference monopole antenna using a VNA (S12) instead of typical signal generator/spectrum analyzer pair. Accuracy of antenna parameters along with the errors made in fabrication process is also discussed in the paper. © 2012 IEEE.Conference Object A study for development of propagation model based on ray tracing for coverage prediction in terrestrial broadcasting systems;(2009) Tabakcioǧlu,M.B.; Özmen,A.; Kara,A.In this work, improvements on propagation prediction models based on ray tracing in coverage estimation for digital broadcasting systems are presented. For this purpose, firstly, propagation models based on Geometrical Theory of Diffraction (GTD) are discussed, and then an improved model is proposed for prediction of propagation path loss or electric field strength at the receiver. The proposed model incorporates first order expansion of classical GTD in field computation and convex hull for ray tracing. Simulation results are presented for comparison of various models in terms of computation time and accuracy. ©2009 IEEE.Conference Object Specific Emitter Identification using video signals;(2012) Erdem,C.; Kara,A.Specific Emitter Identification(SEI) methods are used in intercept systems for differentiating of same type of emitters in the environment. Most of the SEI implementations are designed for post processing (off line) by operators. This paper presents preliminary results on real time (on line)implementation of a SEI method on signals after the IF stage, i.e, video signals after the detector section. Initially, only the envelope of the pulses are considered in SEI processing. Pulse width and energy are two main parameters used in SEI algorithm developed. On the other hand, one of the main problems in operational environments is multipath distotion on received pulses. Most of the SEI algorithms require higher SNR figures for providing reliable results. Moreover, creating and running of a library is another issue. This paper presents various approaches in both processing of multipath distorted pulses and wavelet based library creating methods on real-time SEI implementation for an intercept receiver. © 2012 IEEE.Conference Object Citation - Scopus: 14A Remote Laboratory for Training in Radio Communications: Errl(2007) Kara,A.; Aydin,E.U.; Öktem,R.; Çaǧiltay,N.This paper presents, first, a short survey of remote laboratory initiatives in electrical and computer engineering, and then discusses design and development phases of remote laboratory environment on radio communications, the ERRL (European Remote Radio Laboratory). As being the first attempt in establishing of such a large scale remote laboratory on radio communications, ERRL enables access to high technology RF equipments and setups through the Internet. The software structure, target groups and experimental set ups of ERRL are shortly discussed. First attempts on implementation of pilot experiments are discussed. © 2007 IEEE.Conference Object Citation - Scopus: 2A New Approach To Threat Tracking on Esm Systems by Using Kalman Filters;(2009) Çelebi,M.B.; Kara, Ali; Kara,A.; Akar,B.; Tümay,A.; Dinçer,K.; Kara, Ali; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringKalman filtering (KF) is a form of recursive estimator, which has been widely applied to different applications. This paper discusses a new approach, based on a discrete event process, for tracking of threats (emitters). Pulses of a particular threat from received mixed (raw) pulse sequences of multiple threats corrupted by timing jitter and measurement noises are aimed to be tracked. Required parameters to initiate KF are taken from identification algorithm which begins before KF algorithm. Hereby, KF runs on mixed pulse train. The algorithm based on KF is adaptive to both the noise and missing pulses together with large time gaps between pulses of the threat. The algorithm is robust and efficient due to the fact that it includes various distinctive parameters of the threat such as frequency (TF), pulse width (DG), angle of arrival (GA) and scan patterns (TO). ©2009 IEEE.
