Türkmen, Ceyhan
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Araş.Gör.
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01.01.09.02. Elektrik- Elektronik Mühendisliği
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| Journal | Count |
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| Radio Science | 3 |
| 11th German Microwave Conference (GeMiC) | 1 |
| 12th International Conference on Electrical and Electronics Engineering (ELECO) | 1 |
| 2017 Progress In Electromagnetics Research Symposium - Spring PIERS 2017 | 1 |
| 23nd Signal Processing and Communications Applications Conference (SIU) | 1 |
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Article Compact and Wideband Cavity-Backed Antenna With Elliptical Coupling Slot and Elliptical Aperture for Satellite Communications Transceiver Applications(John Wiley and Sons Inc, 2025) Yavuz Asci; Ceyhan Türkmen; Mustafa Seçmen; Asci, Y.; Secmen, M.; Turkmen, C.A wideband full-metal cavity-backed antenna with elliptical coupling slot and elliptical aperture is proposed. The antenna consists of two elliptical structures a coupling slot and a radiating aperture which are placed on the feed waveguide side and the load side of a rectangular metal cavity resonator respectively. By using an elliptical slot/aperture the impedance bandwidth and gain of the antenna are found to be considerably improved in the same footprint and without increasing complexity compared to rectangular slot/aperture and also circular aperture. A prototype of the proposed wideband antenna is fabricated by using the additive manufacturing techniques of 3D printing with polylactic acid (PLA) material which is covered with aluminum tape to validate the design at Ku-band for satellite communication (SatCom). The measured results show that the antenna has an impedance bandwidth of 4 GHz (10.86–14.86 GHz for |S11| < −15 dB) which gives a fractional bandwidth (FBW) of 31.1%. With low cross-polarization being less than −25 dB at broadside the antenna has a peak gain of 9 dBi. The proposed antenna is also compact with a total volume of about 1.1λ03 at the center frequency. © 2025 Elsevier B.V. All rights reserved.Conference Object A Dual-Band Circularly Polarized Bi-Sectoral Waveguide Horn Antenna for High Power LEOP TT&C Systems(Institute of Electrical and Electronics Engineers Inc., 2022) Esra Alkın; Ceyhan Türkmen; Mustafa Seçmen; Secmen, Mustafa; Turkmen, Ceyhan; Alkin, EsraIn this study a dual-band circularly polarized bi-sectoral waveguide antenna is proposed which is used launch and early orbit phases (LEOP) of telemetry tracking and command (TT&C) applications of satellite systems to almost cover full space together with omni-directional (toroidal) antennas. The structure consists of four parts (pyramidal horn antennas) each having excited by a single inclined slot being cut over circular waveguide. However because the overall antenna is only fed with a single rectangular waveguide it works as transceiver (in TX and RX bands simultaneously). The parts belonging to each band have bi-directional patterns being opposite to each other. Therefore instead of using four separate antennas each being fed by separate rectangular waveguide to cover both directions in dual band (TX and RX bands) in 3D space one antenna with just one feed is demonstrated as being sufficient for same purpose. For this purpose an antenna is designed for a Ku-band TT&C application. The results show that the antenna is dual-band over 500 MHz bandwidth around 11.75 GHz (TX) and 13.75 GHz (RX) center frequencies. The antenna has more than 9.5 dBi peak gain in both main lobes and 15 dB return loss at TX band, and has more than 10 dBi peak gain and 10 dB return loss at RX band. Besides it has less than 3 dB and 3.5 dB axial ratio (AR) values at TX and RX bands within almost 45º and 60º azimuth and elevation beamwidth values respectively. © 2022 Elsevier B.V. All rights reserved.Master Thesis Uydu haberleşme sistemleri için yönsüz antenler(2016) Türkmen, Ceyhan; Seçmen, MustafaIn this thesis, the design, production and measurements of Ku-Band, omnidirectional and circularly polarized antennas, which can be used in satellite communication applications as receiver and/or transmitter, are explained. Ku-Band is a commonly used frequency band in satellite communication applications. These antennas consist of inclined slots (slotted array) placed with a circular symmetry on a circular waveguide. The antenna structures are fed by a special transition from standard rectangular waveguide to this circular waveguide, where the rectangular waveguide is the standard WR75 used frequently in Ku-Band applications. The electromagnetic wave propagates in only dominant TE10 mode inside the rectangular waveguide (main feed of the antenna), while propagating in the second higher order mode of TM01 inside circular waveguide. This TM01 mode is nondominant for circular waveguide; but has circular symmetry in the excitation of the slots on the antenna array, which provides omnidirectional pattern. The mentioned special transition effectively suppresses the dominant TE11 mode and other higher order modes such as TE21 in the circular waveguide, which disturbs symmetry (omnidirectionality) in the radiation pattern. In order to make the antennas circularly polarized, the slotted array elements are designed as inclined way, and parallel metallic plates (disks) are placed around the slotted arrays. Three different versions of the proposed antenna are designed, simulated and implemented. The first one is designed just for transmitting purpose from the satellite to earth, and operates at the frequency about 11.75 GHz. Similarly, the second antenna is realized just for the receiving purpose from the ground segment to satellite. This antenna operates at the frequency about 14.00 GHz. The last antenna design is more sophisticated than the other ones such that it works as a transceiver carrying out transmission at 11.75 GHz and reception at 14.00 GHz simultaneously. According to results obtained for the first two designs, the return loss, which is better than 10 dB, is provided around the frequency regions of both transmitter (11.75 GHz) and receiver (14.00 GHz) within approximately 3 percent frequency bandwidth. In addition, axial ratio is lower than 1 dB in the azimuth plane and lower than 4 dB in a wide beamwidth of elevation plane at the center frequencies. Omnidirectional radiation pattern is provided at azimuth plane such that the variation of gain is about 0.7 dBi at this plane. The transceiver version of the design has frequency bandwidth of about 350 MHz and 500 MHz for the maximum 10 dB return loss around the center frequencies of 11.75 GHz and 14.00 GHz, respectively. The axial ratio values are found to be lower than 2 dB in the azimuth plane for both center frequencies, which corresponds to good circular polarization performance. The values in the radiation patterns change at most 3 dB at the same plane.Conference Object Citation - WoS: 2Citation - Scopus: 11Circularly polarized hemispherical antennas for telemetry and telecommand applications in satellite communication(Institute of Electrical and Electronics Engineers Inc., 2016) Ceyhan Türkmen; Mustafa Seçmen; Secmen, Mustafa; Turkmen, CeyhanThis study describes about Ku-band antennas with circular polarization in hemispherical radiation pattern for telemetry and telecommand applications of satellite communication. The first section of antenna contains a septum polarizer structure which converts linear-polarization to circular-polarizations (left-hand and right-hand). This structure feeds a circular aperture waveguide which is the second part. The axial ratio performance of the antenna is improved by adding some metallic rings with optimized dimensions. Therefore circular polarization is achieved in wider azimuth and elevation angles. Two different designs are carried out for 11.35-11.8 GHz and 14.3-14.65 GHz. The return losses are greater than 15 dB in the given frequency bands. Besides the axial ratio of the antenna is under 3 dB throughout 170° at azimuth and elevation which proves circular polarization property in hemispherical region. The gain at the broadside is almost 9.3 dB and it is higher than -10 dB throughout 170° angle coverage. © 2017 Elsevier B.V. All rights reserved.Article Citation - Scopus: 2The variations of omnidirectional circularly polarized antennas for satellite telemetry/telecommand applications(Istanbul University uosman@istanbul.edu.tr, 2017) Ceyhan Türkmen; Mustafa Seçmen; Secmen, Mustafa; Turkmen, CeyhanIn this paper the design production and results of different types of omnidirectional and circularly polarized antennas for satellite communication applications such as telemetry or telecommand are explained. These antennas consist of identical inclined slots placed on a circular waveguide and two radially outward parallel cylindrical plates in order to provide circular polarization. The feeding of the antenna is provided by a special transition structure between rectangular waveguide to circular waveguide. The first type of antenna contains eight identical slots on the circular waveguide which gives about 3 percent frequency (impedance) bandwidth for 10 dB return loss. This antenna provides gain variation of about 0.7 dBi and axial ratio lower than 1 dB in the azimuth plane at the center frequency. The second type which is designed to enhance the frequency bandwidth includes nonidentical slots on the circular waveguide where the length of four among eight slots is reduced. This enhanced version increases impedance bandwidth to 5.8 percent. The gain variation and axial ratio performances of the second type antenna are slightly lower as compared to first version at the expense of improvement in bandwidth, however the results of both types are still satisfactory for satellite applications. © 2017 Elsevier B.V. All rights reserved.Conference Object Citation - WoS: 1Citation - Scopus: 1A Measurement Technique For Determination of Power Levels of Different Propagation Modes in Circular Waveguides(IEEE, 2020) Ceyhan Turkmen; Esra Alkin; Mustafa Secmen; Secmen, Mustafa; Turkmen, Ceyhan; Alkin, EsraThis study describes a measurement technique for detecting the power levels of different propagation modes in a circular waveguide in the mod converter structure from a rectangular waveguide to a circular waveguide. Specially designed SMA-waveguide adapters are generally used to measure these power levels of propagating modes inside the circular waveguide. While these adaptors can measure power level of desired transmitted mode they are inadequate to obtain suppression levels of other propagation modes simultaneously. Without need of special adapters the technique proposed in this study can determine the amplitudes of different propagation modes in the waveguide at the same time by using 2-port S-parameter values belonging to two identical mode converters. This method has been verified by a rectangular TE10 - circular TM01 mod converter designed and manufactured at center frequency of about 11.4 GHz.Article Citation - WoS: 8Citation - Scopus: 10Omnidirectional and Circularly Polarized Slotted Antenna Array With Increased Bandwidth Performance by Using Nonidentical Waveguide Slots(AMER GEOPHYSICAL UNION, 2018) Ceyhan Turkmen; Mustafa Secmen; Secmen, Mustafa; Turkmen, CeyhanIn this paper the design production and results of an omnidirectional and circularly polarized antenna for satellite communication applications such as telemetry or telecommand are explained. The antenna is fed by a special transition structure between rectangular waveguide to circular waveguide in order to provide symmetrical circular waveguide mode of TM01 and eliminate dominant but asymmetric mode of TE11. The radiation part on the antenna has the geometry of inclined waveguide slots placed in a rotationally symmetric way on a circular waveguide and two radially outward parallel cylindrical plates in order to provide circular polarization. In the design of the antenna nonidentical slots are used on the circular waveguide where half of the total number of slots is reduced to increase the bandwidth of the antenna. The realized antenna is found to give about 5-6% impedance bandwidth around 12GHz where it is just approximately 2.5% when all slots in array are identical. The usage of nonidentical slots results in degradation of gain variation and axial ratio performances as compared to the antennas with identical slots, however it still performs gain variation less than 3dB over full azimuth plane and axial ratio under 3dB over full azimuth plane and elevation beamwidth of minimum 50 degrees for the given bandwidth.Conference Object Citation - Scopus: 1Omnidirectional and Circularly Polarized Transceiver Antenna for TTC Communication in Satellite Systems(Institute of Electrical and Electronics Engineers Inc., 2021) Ceyhan Türkmen; Mustafa Seçmen; Secmen, Mustafa; Turkmen, CeyhanIn this study the design of an omnidirectional and circularly polarized waveguide antenna used as a transceiver in telemetry/telecommand applications of satellite systems is described. Instead of separate transmitter (TX) and receiver (RX) antennas used in space segment the proposed antenna can realize transmit and receive operations (TX/RX) simultaneously which results in the reduction in the number of antennas. The proposed antenna has two sets of inclined slots on circular waveguides with different radii. The below slots operate at TX frequencies around 11.75 GHz and above slots make an effective radiation at RX frequencies around 14 GHz. In the antenna design while metallic disks extending away from circular waveguides improve axial ratio performance a special dual-band rectangular-to-circular waveguide mode converter provides better omnidirectionality. The designed antenna has 10 dB impedance bandwidth more than 150 MHz and 415 MHz at TX and RX frequencies. In azimuth plane gain variation is lower than 2 dBi axial ratio is also lower than 1.63 dB at both frequency bands. In elevation plane minimum gain is found as-5 dBi and axial ratio is below almost 3 dB within 55° beamwidth. © 2021 Elsevier B.V. All rights reserved.Article Citation - WoS: 14Citation - Scopus: 20Dual-Band Omnidirectional and Circularly Polarized Slotted Waveguide Array Antenna for Satellite Telemetry and Telecommand(Institute of Electrical and Electronics Engineers Inc., 2021) Ceyhan Türkmen; Mustafa Seçmen; Secmen, Mustafa; Turkmen, CeyhanIn this letter the design and 3-D-printed manufacturing of an omnidirectional and circularly polarized dual-band antenna for telemetry/telecommand (TMTC) applications in satellite communication on space segment are described. The antenna consists of slotted arrays on the circular waveguide with radially outward metallic disks and choke structures on these disks to improve the omnidirectionality and circular polarization performances. As the main novelty of the antenna design the structure is fed with only one rectangular waveguide, therefore the proposed antenna can be considered as a transceiver antenna. The design and simulations of the antenna and measurement results for 3-D-printed manufacturing are given at Ku-band. A 10 dB return loss bandwidth is found to be 500 MHz both for telemetry and telecommand bands having center frequencies of 12 and 14 GHz respectively. Besides the maximum axial ratio and minimum gain within 65° beamwidth are obtained as 3 dB and-5 dBi respectively which are sufficient for the omnidirectional and circularly polarized antenna providing TMTC communication in satellite systems. © 2021 Elsevier B.V. All rights reserved.Conference Object A Ku-band omnidirectional circularly polarized antenna for telemetry applications in satellite communication(Institute of Electrical and Electronics Engineers Inc., 2015) Ceyhan Türkmen; Mustafa Seçmen; Secmen, M.; Turkmen, C.Ku-band is a frequently used frequency band especially satellite communication application. Telemetry systems collecting measurement or other kind of data are important part especially in the space segment of satellite communication. The antennas in telemetry systems are usually desired to have omnidirectional characteristics in one (usually azimuth) direction. The necessity is much more essential in satellites such that the received/transmitted signal level of satellite should not decrease significantly as the satellite rotates around its rotation axis. Besides the antennas in satellites are required to have circular polarization to get from incoming linearly polarized wave in any orientation angle without any significant power fluctuations. © 2016 Elsevier B.V. All rights reserved.
