Item Open AccessGIS-Aided propagation prediction study for broadcast and telecommunication services(2000) Altıntaş, Ayhan; Aksun, İrşadi; O., Balta; Köymen, Hayrettin; Topçu, Satılmış; Yurchenko, V.; Altıntaş, Ayhan; Aksun, İrşadi; O., Balta; Köymen, Hayrettin; Topçu, Satılmış Item Open AccessMikrodalga karasal radyo link analiz ve simülasyonlarının Rec. ITU-R P.530 tavsiyesine uygun olarak gerçeklenmesi(URSI, 2014) Göktaş, Polat; Topçu, Satılmış; Karaşan, Ezhan; Altıntaş, Ayhan; 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 AccessSabit genişbant kablosuz sistem tasarımı için planlama metodu ve yazılımı(URSI, 2004) Güldoğan, M. Burak; Gürel, Sarper; Topçu, Satılmış; Güldoğan, M. Burak; Gürel, Sarper; Topçu, SatılmışGenişbant Kablosuz Erişim (GKE) sistemleri, nüfus yoğunluğunun yüksek olduğu yerleşim yerlerinde özel ve tüzel ağ kullanıcılarına esnek ve çift yönlü veri dağıtımını sağlayan modern bir teknolojidir. Sabit GKE hakkında yapılan güncel araştırmalar, noktadan-noktaya milimetrik dalga linkleri ve noktadan-alana uç bağlantılarından oluşan iki katmanlı hücresel mimari üzerinde yoğunlaşmaktadır. Bu çalışmada, sabit GKE sistemleri için bir planlama metodu ve makrohücre direkt görünürlük analizi ile mikrohücre kapsama alanı tahmini yapan bir yazılım geliştirilmiştir. Item Open AccessPropagation prediction and planning tools for digital and analog terrestrial broadcasting and land mobile services(2000) Topçu, Satılmış; Köymen, Hayrettin; Altıntaş, Ayhan; Aksun, İrşadi; 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 data Item Open AccessOutdoor propagation models: applications and considerations for real life problems(IEEE, 2003) Altıntaş, Ayhan; Topçu, Satılmış; Köymen, Hayrettin; Moral, Gökhan; Yılmaz, Özgür; 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 AccessDesign of an emergency PMR network based on CDMA 450 in İstanbul metropolitan region(TEHOSS, 2006) Kızılırmak, Çağlar; Topçu, Satılmış; Köymen, Hayrettin; Kızılırmak, Çağlar; Topçu, Satılmış; Köymen, HayrettinIn this work, a complete design of PMR (Professional Mobile Radio) network based on CDMA 450 in ˙Istanbul metropolitan region is presented. Coverage and capacity analysis are performed by the developed simulation software tool. Trade off between several system parameters such as quality of service, user mobility, traffic distribution, data rate and bandwidth are considered to optimize the capacity and coverage of the network. Coverage and handoff areas are shown on the map by the aid of GIS (Geographical Information Systems) tool. System capacity and coverage are presented as the main results of the proposed network. Item Open AccessFeasibility study of installation of solar panels on a high power HF antenna terrain(EMC Türkiye, 2015) Abdul, Ali; Özbey, Burak; Topçu, Satılmış; Altıntaş, Ayhan; Abdul, Ali; Özbey, Burak; Topçu, Satılmış; Altıntaş, Ayhan Item Open AccessA new approach to diffraction modelling for line-of-sight (LOS) paths(IEEE, 2015) Topçu, Satılmış; Göktaş, Polat; Karasan, Ezhan; Altıntaş, Ayhan; 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 AccessOptical 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.; Khan, Talha Masood; Altıntaş, AyhanHighly 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 AccessOptically 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.; Khan, Talha Masood; Altıntaş, AyhanFrequency 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 AccessA GIS-Aided frequency planning tool for terrestrial broadcasting and land mobile services(Springer, Dordrecht, 2002) Topçu, Satılmış; Köymen, Hayrettin; Altıntaş, Ayhan; Aksun, İrşadi; 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 AccessPower spectrum equalized scalar representation of wide-angle optical field propagation(Springer New York LLC, 2018) Külçe, Onur; Onural, Levent; Külçe, Onur; Onural, LeventIt may be desirable to represent optical fields using scalar approximations, due to its simplicity. Since the optical field is an electromagnetic wave, in order to implement an optical setup, a mapping from such a scalar field to the vector electromagnetic field is needed. In the conventional scalar-to-vector field mapping, a large error in power spectrum arises in wide-angle fields due to the neglected large longitudinal component of the electric field. This error could be severe in wide-angle or off-axis imaging setups. In order to find another scalar-to-vector field mapping that compensates for this large magnitude error, first, a general constraint on monochromatic electromagnetic fields to appropriately represent them by a scalar wave in free space is developed. The development of the general constraint begins by formulating the computations of the components of the magnetic field as the outputs of linear-shift invariant (LSI) systems, where the inputs to the LSI systems are the transverse components of the electric field. Furthermore, if one of the transverse components of the electric field can be computed from the other one using a LSI operation, a scalar field, which is related to the transverse components through another LSI system, can be used to fully describe the electromagnetic field. Under this constraint, the required condition on the filters which relates the scalar field to the electric field is presented by taking into consideration the longitudinal component, such that the power spectra of the scalar field and the corresponding electric field are equal. The filters are specified for the electric fields with zero longitudinal component and simple polarization features, as well. Moreover, for the electric fields with simple polarization features, some discrete simulations are performed to compare the scalar field intensity pattern and the corresponding electric field intensity patterns for the conventional and proposed mapping cases. The simulation results show that the excessive amplification of the large frequency components is compensated by the proposed filters, and hence, the undesired effects of the filters used in the computation of the longitudinal component disappear. In this respect, if equality of the power spectra of the scalar field and the corresponding electric field is of concern in an application, the proposed scalar-to-vector wave field mapping should be used. Item Open AccessShort-term propagation measurements and modeling for terrestrial line-of-sight links(IEEE, 2016) Göktaş, Polat; Topçu, Satılmış; Karasan, Ezhan; Altıntaş, Ayhan; 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 AccessFeasibility 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, Ayhan; 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 AccessThe 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, Ezhan; 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  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 AccessPiecewise constant line fitting on noisy ramped signals by particle swarm optimization(IEEE, 2012) Özer, Berk; Altıntaş, Ayhan; Moral, Gökhan; Arıkan, Orhan; 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 AccessMultipath fading effect on terrestrial microwave LOS radio links(IEEE, 2015-07) Göktaş Polat; Topçu, Satılmış; Karasan, Ezhan; Altıntaş, Ayhan; 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 AccessIntegral-equation study of ray effects and natural-mode resonances in a 2-D dielectric prism(IEEE, 2015) Sukharevsky, İlya O.; Altıntaş, Ayhan; 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 AccessComputer 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, Hayrettin; Altıntaş, Ayhan; Ocalı, O.; Topçu, Satılmış; 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 AccessValidation of higher-order approximations and boundary conditions for lossy conducting bodies(Institute of Electrical and Electronics Engineers, 2014-09) Sukharevsky, Ilya O.; Altıntaş, Ayhan; 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.