Browsing by Author "Tutuncu, Bilal"

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A 3-Db 90 Degrees Microstrip Hybrid Directional Coupler at 2.27 Ghz
(Elsevier Gmbh, 2023) Imeci, Mehmet Yusuf; Tutuncu, Bilal; Imecl, Sehabeddin Taha
A 90 degrees hybrid-coupler in the 2.27 GHz range, offering high performance despite its size of 115.64 mm2 (18.36 & lambda;g), is introduced. The main factor that distinguishes this proposed design, positively, is that the device demonstrates high fabrication tolerances due to its simplicity, and uncomplicated length dimensions. At the center of the structure are 9 metal squares, all of equal size and equidistant. It has been observed that the S-parameters remain relatively the same after increasing or decreasing the side lengths, substrate parameters, and the vertical separation dimensions. Based on these results, it has been shown that the design will provide a successful fabrication tolerance. According to the simulation results, the S-parameters are as follows: S11 = -24.01, S12 = -3.063, S13 = -3.063, and S14 = -23.47 (all in dB). The phase deviation is only 0.8 degrees. After the simulation studies, a prototype of the coupler was fabricated, and laboratory measurements were made. The simulated and measured results, have desirable agreement. Finally, a few similar studies presented in the literature are discussed with a comparative table, in terms of overall size, isolation, phase deviation, and structure complexity. Thus, the advantages of this presented structure, compared to these studies, have been revealed.
Effects of 1800 Mhz and 2100 Mhz Mobile Phone Radiation on the Blood-Brain Barrier of New Zealand Rabbits
(Springer Heidelberg, 2024) Kizilcay, Abdullah Oguz; Tutuncu, Bilal; Kocarslan, Mehmet; Gozel, Mahmut Ahmet
In this study, the impact of mobile phone radiation on blood-brain barrier (BBB) permeability was investigated. A total of 21 New Zealand rabbits were used for the experiments, divided into three groups, each consisting of 7 rabbits. One group served as the control, while the other two were exposed to electromagnetic radiation at frequencies of 1800 MHz with a distance of 14.5 cm and 2100 MHz with a distance of 17 cm, maintaining a constant power intensity of 15 dBm, for a duration equivalent to the current average daily conversation time of 38 min. The exposure was conducted under non-thermal conditions, with RF radiation levels approximately ten times lower than normal values. Evans blue (EB) dye was used as a marker to assess BBB permeability. EB binds to plasma proteins, and its presence in brain tissue indicates a disruption in BBB integrity, allowing for a quantitative evaluation of radiation-induced permeability changes. Left and right brain tissue samples were analyzed using trichloroacetic acid (TCA) and phosphate-buffered solution (PBS) solutions to measure EB amounts at 620 nm via spectrophotometry. After the experiments, BBB tissue samples were collected from the right and left brains of all rabbits in the three groups and subjected to a series of medical procedures. Samples from Group 1 were compared with those from Group 2 and Group 3 using statistical methods to determine if there were any significant differences. As a result, it was found that there was no statistically significant difference in the BBB of rabbits exposed to 1800 MHz radiation, whereas there was a statistically significant difference at a 95% confidence level in the BBB of rabbits exposed to 2100 MHz radiation. A decrease in EB values was observed upon the arithmetic examination of the BBB.
Microstrip Antenna for 5g Communication: Design and Performance Analysis
(Ieee, 2020) Tutuncu, Bilal
In this study, a new microstrip antenna is proposed for 5G mobile communication in IEEE802.11ad standard. Hairpin shaped radiating patch is analyzed on three different substrates; FR4, Rogers R054350B and Arlon AD255C. Directivity and bandwidth analyzes based on permittivity are performed to select the most suitable substrate among these three dielectric layers for 60 GHz operating frequency. Rogers RO4350B has 1.17 dBi higher directivity compared to FR-4 and 0.13 dBi smaller directivity gain compared to Arlon AD255C, but offers 2.4 GHz more bandwidth and more compactness than the others. Finally, the proposed antenna is analyzed on four different thickness of Rogers RO4350B and the best performance is observed at 1.2 mm.
Microstrip Filters Based on Open Stubs and Sir for High Frequency and Ultra-Wideband Applications
(Academic Publication Council, 2022) TahaImeci, S.; Tutuncu, Bilal; Beslija, Faruk; Herceg, Lamija
This paper includes two new microstrip filter configurations for high frequency and ultra-wideband applications. The first proposed filter is a composition of four parallel open-circuited stubs connected by optimized fractal-structured microstrip line. The filter response is a combination of three passing regions, namely, low pass from 0.1 GHz to 3 GHz, band-pass from 4.5 GHz to 9 GHz, and high pass from 10.5 GHz to 13 GHz, separated by two rejection regions from 3 GHz to 4.5 GHz and 9 GHz to 10.5 GHz. Deep and sharp rejection regions reaching up to-44.6 dB with 40 % fractional bandwidth (FBW) are observed with a good electrical performance. Furthermore, with a comparative table, the advantages of this proposed BSF in terms of FBW, compactness, and insertion loss are compared with recently reported related studies. Secondly, a dual -band band-pass filter implementing a stepped-impedance resonator (SIR) and a modified H-shaped structure is presented. This filter is designed to operate in a low pass region up to 3.58 GHz and a band-pass region from 15.38 to 21.65 GHz, with a wide stopband region between 4.46 and 14.07 GHz. The simulated and measured results are in good agreement. Compared to its peers, the compact size and low price allow for a wide application of these filter configurations, while passing frequencies allow operation in the unlicensed frequency spectrum, which is popular for high-speed communication.
Microwave Absorber Surface Design for 5g Energy Harvesting Applications
(Iop Publishing Ltd, 2024) Tutuncu, Bilal; Turktam, Ufuk
This study presents a high-efficiency microwave absorber for energy harvesting in 5G frequencies. Initially, a unit cell was designed in four stages to efficiently absorb in the targeted frequency region. The results obtained for each stage of the design were analyzed, and additional investigations were conducted for substrate material and thickness based on the optimum performance of the unit cell structure. A unit cell absorber designed on an FR4 a flame-resistant fiberglass/epoxy-based composite, commonly utilized in printed circuit boards due to its favorable electrical insulation properties and low cost. With a thickness of 1.5 mm, the absorber achieved a 98.04% absorption at 3.8 GHz according to simulation results. Subsequently, this unit cell was separately designed and simulated with different periodic arrays to transform into an absorber surface. As a result, high absorption rates of 98.94% and 98.35% were achieved at 3.8 GHz and 4.2 GHz, respectively, in the 2 x 2 array. It was observed that the structure absorbs over 85% within a 1 GHz bandwidth between 3.5 GHz and 4.5 GHz. Finally, a prototype of the absorber surface was manufactured, and measurements were taken in the laboratory environment. Significant agreement was found between the data obtained from these measurements and the simulation results. The results indicate that the suggested absorber surface is well-suited for energy harvesting within the n77 (3.3 GHz to 4.2 GHz) and n78 (3.3 GHz to 3.8 GHz) bands of 5G communication.
Mutual Coupling Reduction Using Coupling Matrix Based Band Stop Filter
(Elsevier Gmbh, 2020) Tutuncu, Bilal
The capability of the coupling matrix-based band stop filter in mutual coupling reduction between the MIMO arrays is presented. Initially, a microstrip band-stop filter with 3 GHz center frequency is designed using coupling matrix method. This filter structure is then placed between 2 x 1 radiating patches separated by 0.22 lambda in a reference MIMO antenna designed for 3 GHz WiMAX applications. Both array antennas with/without band stop filters are fabricated and the scattering parameters are obtained separately and plotted comparatively. A good agreement is achieved between measurement and simulation results, and about 28 dB isolation is observed at operating frequency after the proposed filter application. Besides, the Envelope Correlation Coefficient (ECC) is computed and surface current distributions are simulated for both cases. It is observed that ECC has dropped to almost zero and the surface currents induced in the second patch due to the first patch excitation are extinguished with the implementation of the proposed isolation wall. Finally, to clarify the advantages of our approach, a few related studies are summarized in a comparative table. (C) 2020 Elsevier GmbH. All rights reserved.
Performance-Enhanced S-Shaped Slotted Patch Antenna for X Band/Ku Band Applications
(Springer, 2023) Imeci, S. Taha; Tutuncu, Bilal; Herceg, Lamija
Design and performance enhancement of an S-shaped antenna with two additional slits and slots is presented. Initially, a parametric study was performed with two commonly used dielectric materials. First, FR4 with er = 4.3 and thickness of 1.55 mm was used, followed by RO4003C with er = 3.55 and thickness of 0.8 mm. Suitable for high frequencies, the RO4003C outperforms the affordable but lossy FR4. Thus, the antenna is fabricated with RO4003C. The simulated and measured results are in good agreement. Since the proposed antenna operates at two resonant frequencies, 10 GHz and 17.65 GHz, it is suitable for both X and Ku bands. The better gain was obtained at 10 GHz, with a measured gain of 6.3 dB. Finally, a comparative table is given, which reveals the superiority of the proposed antenna in terms of gain and compactness over some X-band antennas recently presented.
Substrate Analysis on the Design of Wide-Band Antenna for Sub-6 Ghz 5g Communication
(Springer, 2022) Tutuncu, Bilal; Kosem, Mahmut
While copper is overwhelmingly used as the radiated part in microstrip antenna design studies, the choice of dielectric material offers a wide range of possibilities. At high frequencies, the effect of substrate permittivity on antenna performance is dramatically higher than low frequency microstrip antennas. For this purpose, in this study, a discussion on 4 different dielectric substrates to increase the overall efficiency of conventional sub-6 GHz 5G microstrip antenna is presented. A reference rectangular patch is modeled on FR4, Arlon AD300C, Rogers RO4003C and Mica substrates respectively. The radiating patch sizes are calculated and modeled for each dielectric substrate separately and then optimized for 5.65 GHz. Finally, gain and bandwidth analysis are performed with the help of CST Studio. Arlon AD300C, which is revealed to be the best in performance criteria analysis, is used for the proposed antenna fabrication and the simulated results are verified by bandwidth and gain measurements in a fully anechoic chamber. Finally, the advantages of the proposed antenna over some Sub-6 GHz 5G antennas with randomly selected substrates are confirmed by a comparative table.