Nassor, M.A. | Korkmaz, E. | Yegin, K.

Conference Object | 2014 | 2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014

Planar antennas such as microstrip patch, bowtie, spiral, and modified crossed dipole are designed and simulated at 30 THz. Gains of antennas obtained directly from simulation results are verified using a different technique inspired from radar cross section measurements. Reradiated far field of an antenna when its feed point is open-circuited is obtained with a far-field probe. The proposed method is introduced as an alternative for the signal detection sensitivity measurements of IR detector antennas. © 2014 IEEE.

Isenlik, T. | Yegin, K.

Article | 2013 | IEEE Transactions on Plasma Science41 ( 2 ) , pp.296 - 304

We present a simple design method for the hole-slot-type cavity magnetron. Our design model includes all principal parts of magnetron, namely, the cathode, the resonant system, the interaction space, and the magnetic circuit. We first find structural, electrical, and magnetic parameters using empirical formulas. Then, using empirical values as initial guesses, we build and simulate the 3-D model of magnetron in CST Particle Studio. In CST, we show that the eigenmode solver is essential for proper mode excitation; then, we use particle tracking and particle-in-cell simulations for the desired magnetron operation. For a fast convergen . . .t result, we study the impact of design parameters on the magnetron performance. We apply this design procedure to an X-band hole-slot-type magnetron with eight resonators. We believe that our method provides designers a simple, fast, and reliable tool for hole-slot-type magnetron design. © 2012 IEEE Daha fazlası Daha az

Kocakarin, I. | Yegin, K.

Conference Object | 2017 | 2017 4th International Electromagnetic Compatibility Conference, EMC Turkiye 2017 , pp.296 - 304

Signal penetration into missiles through nose cone and apertures is critical for electro-optical guidance systems, navigation equipment and control of explosive ordnance. Penetrated signals are relatively small but hard to simulate by known computational methods. To corroborate simulation results, we created a scaled version of a missile and placed wire antennas inside this mock missile. The prototype has openings on the nose cone. Measurements are performed for different antenna sizes placed inside the nose cone. These measurements, then, are compared to numerically calculated simulation results. The extent of corroboration and pos . . .sible ways to improve correct prediction of signal coupling are discussed. © 2017 IEEE Daha fazlası Daha az

Şişman, I. | Yegin, K.

Article | 2017 | International Journal of Antennas and Propagation2017 , pp.296 - 304

We propose a simple solution for jamming mitigation of L1 band GPS by electronically switching antenna beam for wide and narrow beamwidths. Assuming the jamming signal is directed from low elevation angles, antenna reception can be made significantly lower at these angles by electronically reconfiguring the antenna beamwidth. Four-element antenna array and one of the elements of the array are designated as antijam (array) mode and normal mode of the antenna. The antenna is placed on a degenerate-ground with symmetric slots in the ground. Front-end configuration for this antenna is also discussed. Simulations and measurements are per . . .formed to validate the proposed design. The antenna achieves more than 15 dB rejection in measurements and more than 20 dB cross-polarization improvement compared to standalone (normal mode) antenna. The system can easily be replaced with existing active antenna to improve antijam capability of the receiver. © 2017 İsmail Şişman and Korkut Yegin Daha fazlası Daha az

Bayrakceken, F. | Yegin, K. | Korkmaz, E. | Bakis, Y. | Unal, B.

Article | 2012 | International Journal of Photoenergy2012 , pp.296 - 304

Polycyclic aromatic hydrocarbon compound, 1,2: 3,4-dibenzanthracene, is spectroscopically analyzed in ethanol. Ultraviolet absorption spectra were taken and fluorescence measurements were performed. From absorption and emission spectra, Stokes' lines were clearly discernible and these shifts were recorded. Being a carcinogenic compound, the detection of 1,2: 3,4-dibenzanthracene presence in the environment as a pollutant with adverse genotoxic effects is vital. © 2012 Fuat Bayrakceken et al.

Tas, M. | Dasdag, S. | Akdag, M.Z. | Cirit, U. | Yegin, K. | Seker, U. | Eren, L.B.

Article | 2014 | Electromagnetic Biology and Medicine33 ( 3 ) , pp.216 - 222

The purpose of this study is to bridge this gap by investigating effects of long term 900 MHz mobile phone exposure on reproductive organs of male rats. The study was carried out on 14 adult Wistar Albino rats by dividing them randomly into two groups (n: 7) as sham group and exposure group. Rats were exposed to 900 MHz radiofrequency (RF) radiation emitted from a GSM signal generator. Point, 1 g and 10 g specific absorption rate (SAR) levels of testis and prostate were found as 0.0623 W/kg, 0.0445 W/kg and 0.0373 W/kg, respectively. The rats in the exposure group were subject to RF radiation 3 h per day (7 d a week) for one year. F . . .or the sham group, the same procedure was applied, except the generator was turned off. At the end of the study, epididymal sperm concentration, progressive sperm motility, abnormal sperm rate, all-genital organs weights and testis histopathology were evaluated. Any differences were not observed in sperm motility and concentration (p > 0.05). However, the morphologically normal spermatozoa rates were found higher in the exposure group (p < 0.05). Although histological examination showed similarity in the seminiferous tubules diameters in both groups, tunica albuginea thickness and the Johnsen testicular biopsy score were found lower in the exposure group (p < 0.05, p < 0.0001). In conclusion, we claim that long-term exposure of 900 MHz RF radiation alter some reproductive parameters. However, more supporting evidence and research is definitely needed on this topic. © 2014 Informa Healthcare USA, Inc. All rights reserved: reproduction in whole or part not permitted Daha fazlası Daha az

Bilgiç, M.M. | Yegin, K.

Article | 2013 | International Journal of Distributed Sensor Networks2013 , pp.216 - 222

Polarization reconfigurable microstrip patch antenna is presented for 2.4-2.5 GHz wireless sensor network and WLAN applications. Dual feed degenerate mode patch is used as the starting point for circular polarization and L-shaped islands which can be connected or disconnected to the main patch via RF switches are placed around the patch. When L-shape structure is connected, the patch radiates in linear polarization modes with either vertical or horizontal polarization depending on the feed being used. When RF switches are not biased, the antenna is in circular polarization mode. Full wave simulations and measurements were carried ou . . .t to validate the design. © 2013 Mustafa Murat Bilgiç and Korkut Yegin Daha fazlası Daha az

Yegin, K.

Article | 2013 | IEEE Transactions on Antennas and Propagation61 ( 9 ) , pp.4775 - 4782

A diversity antenna system with antennas embedded in rear view mirrors of a vehicle is proposed for satellite digital audio radio system. Antenna diversity is needed because hidden antennas exhibit limited capability and composite body vehicles have poor reception due to no ground plane availability. Pattern gain diversity achieved with the proposed system is proven with on-vehicle antenna simulations and gain measurements. Selection combining diversity receiver architecture is also proposed and the system is tested in real time under two fading scenarios: weak satellite signal in dense foliage and multipath terrestrial environment . . .with frequent satellite blockages. In both cases, the diversity system outperformed the reference antenna system with less mutes times (0.6% versus 0.8% in multipath, 0.1% versus 0.25% in dense foliage) and Reed-Solomon block errors (1.75% versus 2.18% in multipath, 0.87% versus 1.18% in dense foliage). The proposed rear-view mirror location is ideal for minimum signal degradation compared to windshield, backlite, and dashboard antenna installations. © 1963-2012 IEEE Daha fazlası Daha az

Bayrakceken, F. | Yegin, K.

Article | 2012 | International Journal of Photoenergy2012 , pp.4775 - 4782

Microwave irradiation at GSM 900/1800 MHz mobile phone frequencies affects the electronic structure of cresyl violet in solution. These changes are important because laser-dye cresyl violet strongly bonds to DNA- and RNA-rich cell compounds in nerve tissues. The irradiation effects on the electronic structure of cresyl violet and its fluorescence data were all obtained experimentally at room temperature. For most laser dyes, this is not a trivial task because laser dye molecules possess a relatively complex structure. They usually consist of an extended system of conjugated double or aromatic ?-bonds with attached auxochromic (elect . . .ron donating) groups shifting the absorption band further towards longer wavelength. Because of the intrinsically high degree of conjugation, the vibrational modes of the molecular units couple strongly with each other. We found that the fluorescence quantum yield was increased from 0.54 ± 0.03 to 0.75 ± 0.01 due to intramolecular energy hopping of cresyl violet in solution which is exposed to microwave irradiation at mobile phone frequencies, and the photonic product cannot be used as a laser dye anymore. © 2012 Fuat Bayrakceken and Korkut Yegin Daha fazlası Daha az

Bilgic, M.M. | Yegin, K.

Article | 2014 | IEEE Antennas and Wireless Propagation Letters13 , pp.157 - 160

A high-gain, wideband antenna element that covers most portions of X-and Ku-bands is essential for multimode radar applications. This letter presents an aperture-coupled stacked patch antenna for 8.75-12.25-GHz frequency band. Fixed beam tilt up to 30^ in scan range can be obtained by offsetting the aperture relative to a driven patch. When there is no offset, a single antenna has broadside gain greater than 10 dBi. An antenna array (4×,4) with fixed beam tilt is designed and validated with measurements. The prototype antenna exhibits 44% fractional bandwidth and maximum gain 20.6 dBi in the target frequency band. © 2014 IEEE.

Koc, G. | Yegin, K.

Article | 2013 | International Journal of Distributed Sensor Networks2013 , pp.157 - 160

Seismic sensors are invaluable for intruder detection and perimeter security. In a typical wireless sensor network application of seismic sensors, the units are battery powered and low power consumption becomes critical while fulfilling system requirements. Although many systems utilize 24-bit ADC for seismic signal processing, we employed 12-bit ADC for low power consumption. Because of this relatively low resolution ADC, preamplifier and filters require careful hardware design. We employ bidirectional T-type filtering, noise reduction, and distributed filtering between gain stages before the signal is input to ADC. The proposed de . . .sign was verified with measurements. Seismic data signals due to footsteps at varying distances were successfully measured. © 2013 Gokhan Koc and Korkut Yegin Daha fazlası Daha az

Isenlik, T. | Yegin, K. | Barkana, D.E.

Article | 2019 | IET Microwaves, Antennas and Propagation13 ( 12 ) , pp.2102 - 2109

It is well known that the beamwidths of horn antennas are inversely proportional to frequency. Previous studies point to minimum ±12% beamwidth stability within a maximum of 2.5:1 bandwidth (BW) ratio. To extend this BW, a design methodology for broadband double-ridged horn antenna (DRHA) is proposed and applied to 4.5–18 GHz frequency band. Firstly, a conventional DRHA is designed and studied to compare the beamwidth variation of wideband horn antennas. By explicitly addressing the shortcomings of conventional DRHA, DRHA is redesigned and near-constant beamwidth DRHA is proposed using the modifications implemented on the sidewalls. . . . The antenna utilises ridges to extend the frequency band, unlike other wideband constant beamwidth horns. The authors show that ridged horns, whose dimensions are appropriately designed and modified, can have stable beamwidths. Then, properly positioned curved pinwalls are designed to provide considerable improvement in H-plane beamwidth constancy. Broadband double-ridged waveguide-to-coaxial adapter is also designed for 50 ? reference. The prototype is manufactured, and the measured antenna exhibits wideband characteristics with 30.9° ± 2.7° half power beamwidth in H-plane over 4:1 BW ratio. This variation corresponds to ±8.7% beamwidth stability along with the target frequency band. © The Institution of Engineering and Technology 2019 Daha fazlası Daha az