Prof. Dr. SİBEL ÇİMEN
'%3e%3cpath%20d='M22.1642%2019.0924C21.7317%2018.068%2021.1041%2017.1375%2020.3163%2016.3527C19.5309%2015.5656%2018.6006%2014.9381%2017.5766%2014.5048C17.5674%2014.5002%2017.5582%2014.4979%2017.5491%2014.4933C18.9774%2013.4616%2019.9059%2011.7811%2019.9059%209.88504C19.9059%206.74408%2017.3611%204.19922%2014.2201%204.19922C11.0792%204.19922%208.53429%206.74408%208.53429%209.88504C8.53429%2011.7811%209.46282%2013.4616%2010.8912%2014.4956C10.882%2014.5002%2010.8728%2014.5025%2010.8636%2014.5071C9.83652%2014.9404%208.91487%2015.5617%208.1239%2016.355C7.33685%2017.1404%206.70933%2018.0707%206.276%2019.0947C5.85031%2020.0972%205.62072%2021.172%205.59967%2022.2609C5.59905%2022.2853%205.60335%2022.3097%205.61229%2022.3325C5.62123%2022.3553%205.63465%2022.376%205.65174%2022.3935C5.66883%2022.4111%205.68926%2022.425%205.71182%2022.4345C5.73437%2022.444%205.7586%2022.4489%205.78308%2022.4489H7.15868C7.25956%2022.4489%207.3398%2022.3686%207.3421%2022.2701C7.38795%2020.5001%208.09868%2018.8425%209.35506%2017.5861C10.655%2016.2862%2012.3814%2015.5709%2014.2201%2015.5709C16.0588%2015.5709%2017.7852%2016.2862%2019.0852%2017.5861C20.3415%2018.8425%2021.0523%2020.5001%2021.0981%2022.2701C21.1004%2022.3709%2021.1807%2022.4489%2021.2815%2022.4489H22.6571C22.6816%2022.4489%2022.7058%2022.444%2022.7284%2022.4345C22.751%2022.425%2022.7714%2022.4111%2022.7885%2022.3935C22.8056%2022.376%2022.819%2022.3553%2022.8279%2022.3325C22.8369%2022.3097%2022.8412%2022.2853%2022.8406%2022.2609C22.8176%2021.165%2022.5907%2020.0989%2022.1642%2019.0924ZM14.2201%2013.8284C13.1678%2013.8284%2012.1773%2013.418%2011.4322%2012.6729C10.6871%2011.9278%2010.2767%2010.9374%2010.2767%209.88504C10.2767%208.83271%2010.6871%207.84227%2011.4322%207.09715C12.1773%206.35204%2013.1678%205.94165%2014.2201%205.94165C15.2724%205.94165%2016.2629%206.35204%2017.008%207.09715C17.7531%207.84227%2018.1635%208.83271%2018.1635%209.88504C18.1635%2010.9374%2017.7531%2011.9278%2017.008%2012.6729C16.2629%2013.418%2015.2724%2013.8284%2014.2201%2013.8284Z'%20fill='%238590A2'/%3e%3c/g%3e%3c/svg%3e)
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Academic Career Length
17Years (2010-Present)
(Calculated once Scilit publication data is synced: current year − year of first publication + 1)
Representative Publications
View All Publications26 March 2014 in IEEE Transactions on Antennas and Propagation
Journal Article
A novel planar octagonal-shaped antenna with reduced radar cross section (RCS) for ultra-wideband (UWB) applications is designed and demonstrated experimentally. The proposed antenna is modified using the geometrical shaping method in order to get the RCS reduction. This method is based on the subtraction of metal areas which have the minimum current distributions on the surface of printed antenna. Both of the reference and modified octagonal-shaped antennas are operating at 2.5-18 GHz frequency range with %151 fractional bandwidths. The full-wave electromagnetic simulations and laboratory measurements are performed to characterize their RCSs as a function of frequency, radiation patterns and scattering characteristics. The radiation performance of modified antenna is stable and consistent with the reference antenna. Also the results show that the designed UWB antenna has lower RCS compared to the reference antenna. About 10 dBsm RCS reduction is obtained in the whole operation bandwidth. The designed antenna has very large RCS reduction up to 25 dBsm, especially in the low frequency range.
1 August 2013 in IET Microwaves, Antennas & Propagation
Journal Article
SİBEL ÇİMENA novel, dual‐band frequency‐selective surface (FSS) is presented. The designed and fabricated FSS structure has closely spaced operation bands and high selective frequency response at each operation band. Two‐dimensional compact U‐shaped slot resonators are used in each FSS unit cell to obtain this ability. Also, each slot resonator is composed of straight slot section at the centre connected to two U‐shaped arms at each end. The dimensions of the slot resonators are optimised using via full‐wave electromagnetic simulations using CST Microwave Solver. The proposed FSS structure is independent of incident polarisation and angle because of 90° rotation of the unit cell. The validity of the proposed FSS is confirmed by both simulation and measurement results. In the experimental verification, a waveguide measurement setup is chosen. Both measurement and simulation results show that the FSS structure operates at the designed frequencies of 8.80 and 9.54 GHz, which are very close to each other.
13 December 2016 in IEEE Antennas and Wireless Propagation Letters
Journal Article
SÜSibel ÜNALDI
Sibel ÜNALDISİBEL ÇİMENGCGonca Cakir
Gonca CakirUAUmut E. Ayten
Umut E. AytenThis study presents a novel ultra-thin dual band frequency selective surface (FSS) for X band applications. The proposed single layer FSS operates as a band reject filter at 8.47 GHz and 10.45 GHz. The ratio of these two operating bands has small value such as 1.23 and it points out that the proposed FSS has closely spaced characteristic. In addition, the designed dual-band single-layer FSS has an ultra-thin thickness of 0.021* $\lambda_{l}$ , where $\lambda_{l}$ is the wavelength of the lower operational frequency. The stable frequency responses are sufficiently achieved for the TE (transverse electric) and TM (transverse magnetic) polarizations by using the proposed FSS. The validity of FSS is obtained by comparing measurements and simulations.
18 April 2018 in IET Microwaves, Antennas & Propagation
Journal Article
A new type of X‐band (8–12 GHz) unit cell structure on a single‐layer for broadband reflectarray antennas is presented in this study. To obtain a broadband performance, a unit cell composed of a circular ring and a complementary diagonal patch ring is proposed. This new type unit cell is designed on a 0.183 × λ 0 (air‐dielectric) thin dielectric substrate and has a 430 ° phasing range with slow phase variation. Based on the wide phase variation of the proposed unit cell, a centre‐fed broadband reflectarray antenna is designed with 9 × 9 unit cells, 81 elements on a square plane geometry. The designed reflectarray has 40% aperture efficiency and 96% antenna efficiency at 10.5 GHz. The validity of the reflectarray antenna is verified through measurement and simulation results. The experimental and simulation results are in good harmony. The measured and simulated results show that the maximum gain of the reflectarray antenna is 21.6 dBi at 10.5 GHz and has 23% 1 dB gain bandwidth and 29% 3‐ dB gain bandwidth. Also, the minimum cross‐polarisation discrimination is 31.2 dB at 11 GHz frequency.
1 June 2014 in IET Microwaves, Antennas & Propagation
Journal Article
In this study, a novel axe‐shaped ultra‐wideband (UWB) antenna with low‐backscattering radar cross‐section (RCS) is designed. The designed UWB antenna bandwidth is 3.4–15.5 GHz covering the entire band assigned for the UWB applications. The RCS of the designed antenna is reduced by modifying the geometrical shape. This technique is based on the subtraction of the metal areas which have the minimum current distributions on the surface of the printed antenna. Therefore the backscattering RCS of the modified axe‐shaped UWB antenna is reduced up to 10 dB in the whole frequency band while maintaining the radiation performance. The size of the antenna is 0.32 λ l × 0.39 λ l , where λ l is the wavelength at the lower operation frequency and the fractional bandwidth is 128%. The radiation patterns, scattering characteristics and the RCS of both the modified and reference axe‐shaped UWB antennas are simulated and experimentally verified. The simulation and measurement results are in a good agreement.
12 April 2019 in Radioengineering
Journal Article
About Me
My research has significantly contributed to the fields of electromagnetic wave propagation, ultra-wideband (UWB) antennas, and frequency selective surfaces (FSS). Among my most cited works are studies on the design and optimization of UWB monopole antennas, which have been widely referenced for their innovative ground plane structures and high gain performance. Another highly cited line of research focuses on polarization-independent band-stop FSS designs for ultra-wideband applications, offering simple structures with excellent frequency stability and angular response.
Additionally, my publications on reflectarray antennas with double cut ring elements for X-band applications have drawn strong academic attention, particularly for combining compact design with enhanced radiation characteristics. Earlier works on metamaterial-based filter and wave-guide structures have also been frequently cited for their novel simulation approaches and experimental validation.
These studies collectively advanced antenna miniaturization, bandwidth enhancement, and electromagnetic filtering technologies, positioning my research as a reference point in the area of applied electromagnetics and microwave engineering.