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AMPS/PCS/GPS active antenna for emergency call systems

Yegin, K.

Article | 2007 | IEEE Antennas and Wireless Propagation Letters6 , pp.255 - 258

Many vehicular emergency call applications utilize a dual-band cellular phone for data exchange and Global Positioning System (GPS) antenna for localization. When the cellular phone antenna is transmitting in close proximity to the GPS antenna, the GPS low-noise amplifier (LNA) is expected to be not affected, i.e., remain linear during the operation. Most commercial GPS LNAs hardly meet this requirement, hence passive antenna-to-antenna isolation and preamplifier filtering without affecting the noise figure of the system becomes crucial. In addition, passive antenna gain requirements for emergency call applications are generally hig . . .her than those of regular dual-band cellular phone antennas. To satisfy all these requirements, a multiple-element antenna is designed, built, and measured. © 2007 IEEE Daha fazlası Daha az

Derivation of Green's Functions for Paraxial Fields of a Wedge with Particular Anisotropic Impedance Faces

Isenlik, T. | Yegin, K.

Article | 2013 | Electromagnetics33 ( 5 ) , pp.392 - 412

Wideband offset slot-coupled patch antenna array for X/Ku-band multimode radars

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.

On-vehicle GPS antenna measurements

Yegin, K.

Article | 2007 | IEEE Antennas and Wireless Propagation Letters6 , pp.488 - 491

Although GPS antennas are commonly used for vehicle applications, their on-vehicle gain patterns are not known well. Especially, when the antenna is mounted at locations other than the roof center, the antenna gain becomes directional at mid-to-low elevation angles. The goal of this letter is to investigate the GPS passive antenna performance at its actual, on-vehicle mounting locations. For four different antenna locations on a sedan vehicle with sunroof, the antenna gain is measured in a quasi-far-field antenna range. The results are also compared to those of finite ground plane, anechoic chamber measurements. © 2007 IEEE.

Wideband high-gain aperture coupled antenna for ku band phased-array systems

Bilgic, M.M. | Yegin, K.

Article | 2013 | Microwave and Optical Technology Letters55 ( 6 ) , pp.1291 - 1295

Aperture coupled microstrip antenna is presented for Ku band phased-array applications. We show that radial open circuit terminated microstrip feed and hourglass aperture shape provide better coupling, high gain, wide bandwidth and small in-band gain variation. Eight-element antenna array with fixed beam tilt is formed and measured to validate simulations. Copyright © 2013 Wiley Periodicals, Inc.

Effect of long-term exposure of 2.4 GHz radiofrequency radiation emitted from Wi-Fi equipment on testes functions

Dasdag, S. | Taş, M. | Akdag, M.Z. | Yegin, K.

Article | 2015 | Electromagnetic Biology and Medicine34 ( 1 ) , pp.37 - 42

The aim of this study was to investigate long-term effects of radiofrequency radiation (RFR) emitted from a Wireless Fidelity (Wi-Fi) system on testes. The study was carried out on 16 Wistar Albino adult male rats by dividing them into two groups such as sham (n: 8) and exposure (n: 8). Rats in the exposure group were exposed to 2.4 GHz RFR radiation for 24 h/d during 12 months (1 year). The same procedure was applied to the rats in the sham control group except the Wi-Fi system was turned off. Immediately after the last exposure, rats were sacrificed and reproductive organs were removed. Motility (%), concentration (× 106/mL), tail . . . defects (%), head defects (%) and total morphologic defects (%) of sperms and weight of testes (g), left epididymis (g), prostate (g), seminal vesicles (g) were determined. Seminiferous tubules diameter (mm) and tunica albuginea thickness (µm) were also measured. However, the results were evaluated by using Johnsen's score. Head defects increased in the exposure group (p<0.05) while weight of the epididymis and seminal vesicles, seminiferous tubules diameter and tunica albuginea thickness were decreased in the exposure group (p<0.01, p<0.001, p<0.0001). However, other alterations of other parameters were not found significant (p?0.05). In conclusion, we observed that long-term exposure of 2.4 GHz RF emitted from Wi-Fi (2420 µW/kg, 1 g average) affects some of the reproductive parameters of male rats. We suggest Wi-Fi users to avoid long-term exposure of RF emissions from Wi-Fi equipment. © 2015 Informa Healthcare USA, Inc Daha fazlası Daha az

Signal detection theory approach to gastroesophageal reflux disease: A new method for symptom analysis of impedance-pH data

Giral, A. | Kurt, R. | Yegin, E.G. | Yegin, K.

Article | 2014 | Diseases of the Esophagus27 ( 3 ) , pp.206 - 213

An accurate reflux-symptom relationship analysis method is an unmet need in gastroesophageal reflux disease (GERD) diagnosis. The aim of this study was to adapt signal detection theory (SDT) approach to reflux-symptom relationship analysis to develop a new diagnosis method. Patients with predominant symptoms of heartburn and regurgitation were enrolled. Proton pump inhibitor (PPI)-responsive and PPI-unresponsive groups were created via interview and PPI trial. Patients then underwent stationary esophageal manometry and 24-hour multichannel intraluminal impedance-pH monitoring. SDT measurement parameters (discriminability: d' and cri . . .terion: c) were calculated using empirically selected time windows (0.5, 1, 2, 3, 4 and 5 minutes). The time window that provided the highest d' value was selected as the optimal time window. A cut-off d' value that optimally separates two groups was found using receiver operating characteristics analysis. Sixty-three patients completed the study (45 PPI responsive). Optimal time window and cut-off d' value were found as 1 and 0.767 minute, respectively. Symptom association probability (SAP) index values showed good correlation (rS = 0.7182, P < 0.0001) with d' values. SDT approach to reflux-symptom relationship analysis showed sensitivity (89% vs. 78%) and negative predictive values (75% vs. 60%) favorable over SAP index analysis. SDT approach using 1-minute time window and 0.767 cut-off d' value provides us a new and more accurate measure of reflux-symptom relationship than SAP index analysis. © 2013 Wiley Periodicals, Inc. and the International Society for Diseases of the Esophagus Daha fazlası Daha az

Diversity antenna system for satellite digital audio radio

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

Millimeter wave detection of landmines

Öztürk, H. | Nazli, H. | Yegin, K. | Biçak, E. | Sezgin, M. | Dag, M. | Türetken, B.

Conference Object | 2013 | Proceedings of SPIE - The International Society for Optical Engineering8709 , pp.4775 - 4782

Millimeter wave absorption relative to background soil can be used for detection landmines with little or no metal content. At these frequencies, soil and landmine absorb electromagnetic energy differently. Stepped frequency measurements from 20 GHz to 60 GHz were used to detect buried surrogate landmines in the soil. The targets were 3 cm and 5 cm beneath the soil surface and coherent transmission and reflection was used in the experimental setup. The measurement set-up was mounted on a handheld portable device, and this device was on a rail for accurate displacement such that the rail could move freely along the scan axis. Measure . . .ments were performed with network analyzer and scattering data in frequency domain were recorded for processing, namely for inverse Fourier Transform and background subtraction. Background subtraction was performed through a numerical filter to achieve higher contrast ratio. Although the numerical filter used was a simple routine with minimal computational burden, a specific detection method was applied to the background subtracted GPR data, which was based on correlation summation of consecutive A-scan signals in a predefined window length. © 2013 SPIE Daha fazlası Daha az

Micro size detector antennas at 30 THz

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

Conference Object | 2014 | 2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014 , pp.4775 - 4782

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.

RF environment simulation on software defined radio platform

Icin, O. | Yegin, K.

Conference Object | 2017 | 2017 4th International Electromagnetic Compatibility Conference, EMC Turkiye 2017 , pp.4775 - 4782

Evolution of modern communications and radar systems have steadily increased the demand on modelling the propagation effects with real world scenarios for various signal types. The main purpose of this research is to create a flexible, generic and realistic Radio Frequency (RF) environment simulator including both radar and communication signals. Software defined radio (SDR) platform has been utilized for generating the simulated signals at radio frequencies. Power and delay profiles, frequency selective fading, Doppler effect and noise have been calculated for multiple paths and generated via RF outputs of the SDR. RF outputs of th . . .e system is suitable for use in the tests of receivers like direction finding systems and LTE MIMO systems. Communication quality for various terrain profiles and fading scenarios has been experimentally investigated for several signal types using vector signal generators, vector signal analyzers, demodulation and communication analysis tools. This simulation platform can be used in Electromagnetic Compatibility tests of such systems as well. © 2017 IEEE Daha fazlası Daha az

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