Browsing by Author "Alkin, Esra"

Now showing 1 - 3 of 3

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: 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.