Communications and Spectrum Management Research Center (ISYAM)
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Browsing Communications and Spectrum Management Research Center (ISYAM) by Author "Altıntaş, Ayhan"
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Item Open Access Computer aided frequency planning for the radio and TV broadcasts(Institute of Electrical and Electronics Engineers, 1996-06) Altıntaş, Ayhan; Ocalı, O.; Topçu, Satılmış; Tanyer, S. G.; Köymen, HayrettinThe frequency planning of the VHF and UHF broadcasts in Turkey is described. This planning is done with the aid of computer databases and digital terrain map. The frequency offset is applied whenever applicable to increase the channel capacity. The offset assignment is done through simulated annealing algorithm. The international rules and regulations concerning Turkey are also considered.Item Open Access The effect of terrain roughness in the microwave line-of-sight multipath fading estimation based on Rec. ITU-R P.530-15(IEEE, 2014-08) Göktas, Polat; Altıntaş, Ayhan; Topçu, Satılmış; Karasan, EzhanMultipath fading is an important constraint on the prediction of path loss for terrestrial line-of-sight microwave links. The International Telecommunication Union - Radiocommunication (ITU-R) Rec. P.530 [1] is one of the most widely used methods providing guidelines for the design of terrestrial line-of-sight links. The purpose of the study presented in this paper is to make an investigation of the effect of both terrain roughness and geoclimatic factor parameters in the path loss characteristics of microwave line-of-sight (LOS) propagation in NATO Band 3+ (1350-2690 MHz) and NATO Band 4 (4440-5000 MHz) frequency ranges. The two parameters led to significantly different results for the link availability due to multipath fading as a function of the fade margin. © 2014 IEEE.Item Open Access Feasibility study of installation of solar panels on a high power HF antenna land(John Wiley and Sons Inc., 2016) Ali, Abdul; Özbey, Burak; Topçu, Satılmış; Altıntaş, AyhanIn HF broadcasting, the transmitters are typically very powerful. In the case of Turkish Radio and Television (TRT), total transmission average power may reach up to 5 MW. Therefore, it is natural to utilize solar panels as a means of alternative/backup energy for the continuous transmission of RF signal satisfying the requirement of broadcasting. In the TRT HF broadcasting array field, two areas are designated as the candidate areas for solar panel installation. In these areas, electric fields are simulated, measured, and compared. Simulations are done using the Numerical Electromagnetic Code (4nec2). The suitability of the regions for the solar panel installation are evaluated based on the ICNIRP human exposure limits. In addition, 4nec2 simulations are used to see the effect of metal frames of solar panels on the radiation patterns of the short-wave antenna arrays in the two solar panel candidate areas of TRT HF broadcasting station. Simulation results show that metal frames do not seem to have a significant effect on the radiation patterns of the short-wave antenna arrays.Item Open Access Feasibility study of installation of solar panels on a high power HF antenna terrain(EMC Türkiye, 2015) Abdul, Ali; Özbey, Burak; Topçu, Satılmış; Altıntaş, AyhanItem Open Access A GIS-Aided frequency planning tool for terrestrial broadcasting and land mobile services(Springer, Dordrecht, 2002) Topçu, Satılmış; Köymen, Hayrettin; Altıntaş, Ayhan; Aksun, İrşadi; Briggs, D. J.; Forer, P.; Järup, L.; Stern, R.Radio provides an important technology for emergency preparedness and emergency response. It not only offers rapid communication for emergency workers within the disaster area, but also affords the means of disseminating early warning of disasters and advice on how to respond to the public, and a means of monitoring of events and follow-up work in the wake of a disaster. Effective telecommunications are thus a vital part of emergency planning and response (Cate 1994, DHA 1995, Mulilis 1995, Zimmerman 1997). How well radio-based systems work, however, depends on a range of factors, including their geographic coverage, their population coverage, their field strength and their received power level. All these factors are highly dependent upon terrain. Moreover, due to the growing demands on the radio-frequency spectrum, there is a need to improve spectrum management techniques. The increase in the shared use of spectrum among administrations requires the use of more complex analysis methods. The efficient solution of spectrum managementproblems depends upon data storage and analysis capabilities, andconsequently requires the application of computer-aided techniques for data management and frequency assignment.Item Open Access GIS-Aided propagation prediction study for broadcast and telecommunication services(2000) Altıntaş, Ayhan; Aksun, İrşadi; O., Balta; Köymen, Hayrettin; Topçu, Satılmış; Yurchenko, V.Item Open Access Integral-equation study of ray effects and natural-mode resonances in a 2-D dielectric prism(IEEE, 2015) Sukharevsky, İlya O.; Altıntaş, AyhanWe analyze the interplay of two different types of electromagnetic behavior demonstrated by a 2-D dielectric prism: Geometrical Optics and resonance. As it is shown, the first is responsible, for instance, for enhanced reflection from an isosceles 90-degree prism of arbitrary epsilon and size, if illuminated from the base. The second is responsible for the peaks in the total scattering and absorption cross-sections (RCS) at the natural-mode frequencies. The numerical model is based on Nystrom discretization of Muller-type integral equations that provides guarantied convergence.Item Open Access Mikrodalga karasal radyo link analiz ve simülasyonlarının Rec. ITU-R P.530 tavsiyesine uygun olarak gerçeklenmesi(URSI, 2014) Göktaş, Polat; Topçu, Satılmış; Karaşan, Ezhan; Altıntaş, AyhanBu çalışmada, NATO Band 3+ (1350 – 2690 MHz) ve NATO Band 4 (4400 – 5000 MHz) frekanslarında çalışan karasal mikrodalga radyo linklerin analizi için gerekli olan yansıma noktası hesabının iyileştirilmesi ve yansımadan dolayı oluşan çok yollu sönümlenme yayılım mekanizmasının en kötü aydaki link kullanılabilirliğinin hesaplanması ele alınmıştır. TX (verici) ve RX (alıcı) istasyonlarının koordinat bilgileri, radyo linkin TX ve RX istasyonları arasındaki mesafesi, TX ve RX antenlerinin yerden yükseklikleri ve kazançları, polarizasyon tipi, radyo kırılma indisi, zamanın yüzdesi, SNR, sayısal arazi yükseklik haritası ve iklimsel veriler gibi yayılım parametreleri kullanılarak çeşitli linkler için analizler yapılmıştır. Yağmur ve atmosferik gazlardan kaynaklanan zayıflamayı dikkate alarak alıcıdaki güç seviyesi hesaplanmıştır ve yansımadan kaynaklanan çok yollu sönümlenmenin en kötü aydaki link kullanılabilirliği üzerindeki etkileri incelenmiştir.Item Open Access Multipath fading effect on terrestrial microwave LOS radio links(IEEE, 2015-07) Göktaş Polat; Topçu, Satılmış; Karasan, Ezhan; Altıntaş, AyhanIn this paper, the calculation of both the total received power with the effect of the ground reflection and the fade margin to find out the link availability for terrestrial microwave LOS (line-of-sight) radio links is proposed. The expressions are derived from clear-air, rainfall propagation mechanisms and multipath fading due to multipath arising from surface reflection along the defined microwave LOS radio link. We verify the mathematical model by using the ATDI ICS telecom software over sample microwave LOS radio links located in Turkey. © 2015 IEEE.Item Open Access A new approach to diffraction modelling for line-of-sight (LOS) paths(IEEE, 2015) Topçu, Satılmış; Göktaş, Polat; Karasan, Ezhan; Altıntaş, AyhanIn this paper, we present a new knife-edge diffraction method based on Bullington method for the terrestrial line-of-sight (LOS) paths. The diffraction loss of our new knife-edge diffraction method is compared with the results obtained from the Delta-Bullington method and the measurement data existing in the literature for sample fixed terrestrial microwave line-of-sight (LOS)/ non line-of-sight (NLOS) radio links. The revised Bullington method is shown to perform significantly better than the Delta-Bullington method for both overland and coastal/overwater radio links.Item Open Access Optical characterization of high and low resistive silicon samples suitable for reconfigurable antenna design(Wiley Periodicals, Inc., 2018) Ali, A.; Topalli, K.; Ramzan, M.; Khan, Talha Masood; Altıntaş, Ayhan; Colantonio, P.Highly resistive (HR) silicon (Si) can behave as a switch when illuminated by optical source of suitable wavelength. Different reconfigurable passive structures, such as filters, waveguides, and antennas, can be constructed using such silicon switches. This letter presents experimental characterization of high and low resistive (HR & LR) silicon for switching application. In the experiment, HR Si is modeled on a switched transmission line by halogen lamp and a laser source. The experiment of utilizing halogen lamp for Si switch characterization is cost‐effective and can assist engineers in designing reconfigurable antennas. In future, this experiment could be utilized in designing novel reconfigurable antennas.Item Open Access Optically reconfigurable planar monopole antenna for cognitive radio application(Wiley Periodicals, Inc., 2019) Ali, A.; Topalli, K.; Ramzan, M.; Alibakhshikenari, M.; Khan, Talha Masood; Altıntaş, Ayhan; Colantonio, P.Frequency reconfigurable antenna is one of the important elements needed for cognitive radio application. Such antenna can be designed using highly resistive (HR) silicon (Si) operating as an optical switch. This letter presents a novel frequency reconfigurable planar monopole antenna suitable for cognitive radio application. The antenna is designed using HR Si working as an optical switch. The main idea behind the design of antenna is the redistribution of surface current on the antenna while changing the state of Si switches optically from high resistance to low resistance. The antenna is highly compact and uses only two switches for multiband reconfiguration. It is switchable on 1.9 GHz, 2.75 GHz, 3.7 GHz, 4.1 GHz, 4.6 GHz, 4.8 GHz, and 7.6 to 11 GHz frequency bands. Simulated and measured results are presented for the antenna. To the best of authors knowledge, this is the first multiband optically reconfigurable planar monopole antenna.Item Open Access Outdoor propagation models: applications and considerations for real life problems(IEEE, 2003) Altıntaş, Ayhan; Topçu, Satılmış; Köymen, Hayrettin; Moral, Gökhan; Yılmaz, ÖzgürImplementation of propagation prediction models is discussed. It is shown that for real terrain and building data, the additional parameters and assumptions must be made. The determination of coverage percentages for digital communication is discussed. The results indicate that the field strength predictions depend on the implementation of the model.Item Open Access Piecewise constant line fitting on noisy ramped signals by particle swarm optimization(IEEE, 2012) Özer, Berk; Altıntaş, Ayhan; Moral, Gökhan; Arıkan, OrhanIn this study, Particle Swarm Optimization(PSO) is proposed for change point (edge) detection on noisy ramped signals. By taking moving averages between detected edges, noise on ramped signals is filtered and desired piecewise constant signals are acquired. It is required to detect edges in the immediate vicinity of actual edges. Performance of PSO is measured by the difference between estimated and actual position of edges. It is not possible to satisfy such a condition by standard PSO. Hence, in this work, two modifications to standard PSO are proposed: "PSO with uniformly distributed position vectors" and "Cascading PSO". Throughout this work, all implementations are done on real signals which indicate generated powers by plants. © 2012 IEEE.Item Open Access Propagation prediction and planning tools for digital and analog terrestrial broadcasting and land mobile services(2000) Topçu, Satılmış; Köymen, Hayrettin; Altıntaş, Ayhan; Aksun, İrşadiThe problem of efficient utilization of the radiofrequency spectrum is becoming more complex due to the increasing demands on the spectrum, which is a limited natural resource. If this natural resource is to be used efficiently, administrations need to use advanced Automated Spectrum Management Systems (ASMS) which would facilitate national spectrum management and monitoring, coordination among administrations and notification to International Telecommunication Union (ITU). This paper presents some of the spectrum engineering analysis and planning tools of the National Frequency Management System (NFMS) as part of the ASMS which has been developed for the administration of Turkey. This system includes a Relational Database Management System (RDBMS) to support a database containing frequency assignment data, licence holder data and equipment characteristics data. The software is integratedwith a Geographic Information System (GIS) and it has the capability of using digital terrain data and geographic dataItem Open Access Short-term propagation measurements and modeling for terrestrial line-of-sight links(IEEE, 2016) Göktaş, Polat; Topçu, Satılmış; Karasan, Ezhan; Altıntaş, AyhanThis paper presents a propagation prediction technique to predict propagation mechanisms for fixed terrestrial line-of-sight (LOS) radio links, especially proposed for rural environments. We report the results of a short-term propagation measurement campaign carried out in the area of Ankara, Turkey. The field measurements were performed at the frequency of 2.536 GHz for a period of three months in summer 2015. It is observed that the difference between measurement data and predicted mean received power is smaller than the standard deviation value provided by Recommendation ITU-R P. 1546.Item Open Access Validation of higher-order approximations and boundary conditions for lossy conducting bodies(Institute of Electrical and Electronics Engineers, 2014-09) Sukharevsky, Ilya O.; Altıntaş, AyhanThe problem of high-frequency diffraction by a smooth lossy body with high conductivity is considered. In addition to the geometrical optics approximation, additional asymptotic terms are derived to take into account the curvature of the boundary and material properties. Since these higher-order terms are derived by taking into account exact boundary conditions, it is easy to learn about the limitations of impedance conditions and to determine more accurate approximate conditions. The obtained higher-order boundary conditions and their limitations are numerically validated by solving Muller's second-kind integral equations. © 2014 IEEE.Item Open Access Validity and limitations of the median-line integral equation technique in the scattering by material strips of sub-wavellength thickness(Institute of Electrical and Electronics Engineers, 2014-07) Sukharevsky, Ilya O.; Shapoval, O. V.; Altıntaş, Ayhan; Nosich, A. I.Considered is the 2-D scattering of a plane wave by a thin flat material strip. The data obtained by using the empirical method of generalized boundary conditions and singular integral equations on the strip median line are compared with the results of solving the Muller boundary integral equation that takes full account of strip thickness. Discretization of integral equations in both cases is performed using the Nystrom methods that lead to convergent algorithms. Numerical results cover E and H polarizations and two types of thin strips: conventional dielectric and metal in the optical range. The validity and limitations of approximate model are established and discussed.