Browsing by Author "Turkmen, Ceyhan"

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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, Esra
In 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.
Citation - WoS: 1
Citation - Scopus: 1
A 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, Esra
This 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.
Citation - WoS: 4
Citation - Scopus: 4
Base station antenna with enhanced cross polarization discrimination performance by using horizontal meandered dipoles and vertical parasitic elements
(Advanced Electromagnetics, 2019) Orhan Murat Kadagan; Ceyhan Türkmen; Mustafa Seçmen; Kadagan, Orhan Murat; Secmen, Mustafa; Turkmen, Ceyhan
In this study the design and implementation of a ±45° dual polarized base station antenna with improved cross-polarization discrimination (XPD) values are presented. In order to increase the cross polarization parasitic elements are added to antenna design which are formed by two orthogonal dipoles above ground plane. The overall antenna and radiator sizes are diminished by using meandered dipoles. The designed compact antenna has VSWR of 2:1 within 1.71-2.69 GHz frequency band which covers GSM 1800/3G/LTE bands. In the given bandwidth minimum gain of the designed antenna is 0 dBi within the beamwidth of 120° (± 60°) at azimuth plane (ϕ = 0°). Minimum XPD value of 2 dB is achieved between 1.71-2.4 GHz for ±60° beamwidth without parasitic elements where XPD values are improved to minimum 10 dB by using thick parasitic elements. The designed antenna is manufactured where return losses for both port 1 and port 2 are measured to be higher than 10 dB and the isolation between ports is more than 20 dB. In addition the measured peak gain values are varied between 3 dB and 7 dB in frequency range of 1.71 GHz-2.69 GHz. XPD values are measured better than almost 10 dB in the given frequency band. © 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 11
Circularly 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, Ceyhan
This 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.
Citation - WoS: 1
Compact dual-band rectangular TE10 mode to circular TM01 mode converter for telemetry/telecommand applications in satellite communication: design equivalent circuit modeling mode level measurement technique and 3d printed manufacturing
(Tubitak Scientific & Technological Research Council Turkey, 2022) Esra Alkin; Ceyhan Turkmen; Mustafa Secmen; Secmen, Mustafa; Turkmen, Ceyhan; Alkin, Esra
In this study the design of a dual-band mode converter which provides transition from rectangular waveguide TE10 mode to circular waveguide TM01 mode and operates simultaneously in telemetry/telecommand (TT&C) frequencies is presented along with its equivalent circuit and a mode level measurement technique. This dual-band converter is designed to uniformly excite TT&C slot antennas used in satellite communication with symmetric circular TM01 mode. The structure can work as a transceiver due to having one common rectangular waveguide feed. As a Ku-band application a converter giving high purity TM01 mode at circular waveguide at 11.75 GHz/TX and 13.75 GHz/RX center frequencies is designed and manufactured with 3D printing technology. Approximate equivalent circuit models of the designed structure are extracted by using lumped elements from simulated S-parameter results. In addition a measurement technique to detect the normalized power levels of different propagation modes in dual-band mode converter is applied on the manufactured structures to obtain transmission levels of circular TM01 mode and suppression levels of circular TE11 mode. It is revealed from the measurement results that while the designed structure gives more than 17.5 dB return loss and suppression of TE11 mode and less than 0.6 dB insertion loss of TM01 mode within 500 MHz bandwidth at TX band it gives more than 23 dB return loss and suppression of TE11 mode and less than 0.3 dB insertion loss of TM01 mode within 900 MHz bandwidth at RX band.
Citation - WoS: 6
Citation - Scopus: 7
Compact Planar Folded Monopole Antenna with Coupling Mechanism for Quad ISM Band GNSS and UMTS Applications
(IEEE, 2018) Ali Selek; Ceyhan Turkmen; Mustafa Secmen; Selek, Ali; Secmen, Mustafa; Turkmen, Ceyhan
This study presents a compact meandered type monopole antenna improved with coupling mechanisms to increase the number of allocated frequency bands in consideration. The proposed antenna includes a meandered (folded) conductor structure. Two straight conductors placed at the end of the meandered part bring Industrial Scientific and Medical (ISM) bands at the upper UHF band with coupling mechanism and one stub-like conductor inserted at the input of the meandered region gives another ISM band at the higher frequency. The antenna works at four popular ISM frequency bands of 433 866 915 MHz and 2.4 GHz which cover several wireless applications such as M-bus M2M IoT LoRa RFID Wi-Fi and Bluetooth. Along with the optimized dimensions of meandered and straight conductor parts the proper arrangement of the dimensions related with coplanar feed part additionally provides upper Global Navigation Satellite System (GNSS) band which includes upper bands of GPS GLONASS Galileo applications and almost full coverage of 3G/UMTS-2100/IMT-2000 band. The described antenna has compact structure with about 0.125 lambda(0) by 0.046 lambda(0) at the lowest frequency reasonable gain and omnidirectional radiation pattern characteristics.
Citation - WoS: 14
Citation - Scopus: 20
Dual-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, Ceyhan
In 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.
Citation - WoS: 8
Citation - Scopus: 10
Omnidirectional 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, Ceyhan
In 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.
Citation - Scopus: 1
Omnidirectional 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, Ceyhan
In 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.
Citation - WoS: 3
Citation - Scopus: 4
Omnidirectional and Circularly Polarized Waveguide Circular Slot Antenna Array for Satellite Communication
(IEEE, 2016) Ceyhan Turkmen; Mustafa Secmen; Secmen, Mustafa; Turkmen, Ceyhan
In this paper the design of omnidirectional and circularly polarized antennas which can be used in satellite communication is explained. These antennas consist of circular slotted array placed symmetrically on a cylindrical waveguide. The feeding of this cylindrical waveguide is provided with a special transition from rectangular waveguide to cylindrical waveguide. In order to provide circular polarization parallel metallic plates are attached to the aperture of circular slotted array. As the result of the designs better than 10 dB return loss is found in the frequency region of both transmitter (around 11.75 GHz) and receiver (around 14 GHz) within approximately 3 percent frequency bandwidth. Besides there is lower than 1 dB axial ratio in the azimuth plane and lower than 4 dB axial ration in a wide beamwidth of elevation plane. The variation of about 0.7 dBi is observed in the gain at the azimuth plane which provides omnidirectionality at this plane.
Citation - WoS: 3
Citation - Scopus: 5
Printed Quasi Yagi Antenna with Closely Spaced and Thick Directors for Triple ISM-Band/Wideband Applications at UHF
(IEEE, 2018) Ceyhan Turkmen; Yigit Bakirli; Mustafa Secmen; Mehmet Altuntas; Secmen, Mustafa; Turkmen, Ceyhan; Bakirli, Yigit; Altuntas, Mehmet
In this study a printed quasi Yagi antenna realized for almost whole UHF band is given. Within overall UHF band the performances of three well-known ISM frequencies of 433 866 and 915 MHz which are used in many wireless applications such as LoRa IoT M2M M-bus and RFID are desired to be kept relatively better. The proposed antenna includes a printed feed dipole with reflector and two director elements. The directors are quite thick and closely spaced to feed dipole which provides significant enhancement in the bandwidth. According to gathered results the antenna has more than 80% bandwidth for S11 < -6.5 dB between 407 and 955 MHz where return loss values are higher than 10 dB in the bands 417-493 MHz and 700-920 MHz covering three mentioned UHF ISM bands. Additionally it has more than 10 dB front-to-back ratio and 4 dBi realized gain for the frequencies lower than 500 MHz and higher than 850 MHz which again includes 433/866/915 MHz bands, while the gain values in the remaining band are relatively low as being 3.5 dBi on the average.
Citation - WoS: 2
Citation - Scopus: 2
Radar target classification for resonance scattering region targets with min-norm signal processing method
(Institute of Electrical and Electronics Engineers Inc., 2016) Ceyhan Türkmen; Mustafa Seçmen; Secmen, Mustafa; Turkmen, Ceyhan
This paper presents a radar target classification method using high-resolution Min-Norm (minimum norm) technique to discriminate targets in a selected target database. The method is convenient for the targets at the resonance scattering region where the length and other dimensions of the targets are on the order of the wavelength range of the incident fields. The method mainly needs certain number of reference scattered fields obtained from different cases (aspect angle/polarization) for each target. These gathered scattered fields are then processed with Min-norm method and averaged in order to construct one specific Min-norm vector for every targets. These vectors which contain valuable information about resonance frequencies (poles) of the targets are selected as the main features for targets and stored for the classification. In the classification phase a decision based on template matching approach is given according to similarity between test Min-norm vector and feature vectors. The proposed method is demonstrated for wire-based small-scale models of airplane targets and sufficiently high correct decision rates are achieved even for very noisy signals. © 2017 Elsevier B.V. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
The Design of an Omnidirectional and Circularly Polarized Ku-Band Antenna for Satellite Communication
(IEEE, 2015) Ceyhan Turkmen; Mustafa Secmen; Secmen, Mustafa; Turkmen, Ceyhan
This study describes about a Ku-band antenna with almost circular polarization in omnidirectional azimuth direction. The antenna structure contains two sections of inclined slotted array on a circular waveguide and the waveguide is terminated with a matched load. The structure is fed a rectangular waveguide and a rectangular-to-circular waveguide transition. The designed antenna has 10 dB return loss bandwidth is about 3 percent which is usually sufficient for the most of the satellite communication applications in Ku-band. Besides the axial ratio of the antenna is also sufficiently low within the most of the frequency band as providing circular polarization. Besides the radiation pattern of the antenna at azimuth plane is uniform such that the designed antenna is said to have the omnidirectional characteristics at this plane.
Citation - Scopus: 2
The 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, Ceyhan
In 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.