Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 1Citation - Scopus: 1An Improved Pointing Error Model for Mmwave and Thz Links: Antenna and Array Design Impact(IEEE-Inst Electrical Electronics Engineers inc, 2025) Ahrazoglu, Evla Safahan; Gul, Ahmet Caner; Akinci, Mehmet Nuri; Altunbas, Ibrahim; Erdogan, EylemPointing error has a significant impact on the performance of millimeter wave (mmWave) and terahertz (THz) communications due to directional transmission. Currently existing pointing error models are lacking in capturing the mmWave/THz radiation characteristics and/or the impact of antenna design and array design. Therefore, in this letter, a simple analytical pointing error model for highly directional mmWave/THz transmission is proposed. By utilizing the Gaussian beam approximation for both the array element radiation pattern and the array factor, the presented model incorporates antenna design parameters (maximum gain and 3 dB beamwidth) and array design parameters (number of array elements, element spacing, and 3 dB beamwidth). This approximation is validated via electromagnetic simulations in CST Microwave Studio. Afterwards, the statistics of the pointing error are derived according to the Gaussian beam approximation, and it is demonstrated that the pointing error follows a special case of the negative log-Gamma distribution with the shape parameter of 2 and the scale parameter depending on antenna/array design and jitter variance. It is shown that the proposed model aligns perfectly with the simulation results. Moreover, the outage performance of an aerial communication scenario is analyzed to examine the impact of pointing errors. The results have revealed that the antenna and array design parameters are as influential as the jitter variance, and they cannot be neglected.Article Citation - WoS: 3Citation - Scopus: 4Liquid Metal-Controlled Dual-Band Doppler Radar for Enhanced Velocity Measurement(IEEE, 2024) Karatay, Anıl; Yaman, FatihDoppler radars, which are critical instruments for velocity measurement, may need to be reconfigured to adapt to different environmental conditions or for ease of use. However, conventional electrical, optical, and physical reconfiguration methods often come with several disadvantages such as deteriorated radiation pattern, reduced radiation efficiency, and high cost. Therefore, the aim of this article is to integrate microwave components that can be controlled using liquid metal (LM) displacement into a Doppler radar to adjust its main lobe direction and operating frequency to the desired values and enhance the measurement capacity of the respective radar. Through this study, multiple parameters of an operational Doppler radar have been simultaneously adjusted using LM displacement exploitation for the first time, thus avoiding the shortcomings associated with conventional reconfiguration methods. To achieve this objective, initially, a back-to-back Vivaldi antenna operating at 2.45 GHz is designed, and beam switching ability is imparted to the structure using the LM displacement method. Subsequently, various techniques are used to convert the structure into a dual-band antenna capable of simultaneous operation at 2.45 and 5.8 GHz, ensuring the desired beam switching feature at both the frequencies. In addition, a power divider capable of switching between the two operating frequencies through LM assistance is proposed, and its integration into the radar system enables the control of both main lobe direction and frequency using the proposed method.Article Citation - WoS: 34Citation - Scopus: 37Metamaterial antenna designs for a 5.8-GHz Doppler radar(IEEE, 2020) Yılmaz, Hasan Önder; Yaman, FatihThe aim of this paper is to investigate applicability and the effectiveness of the metamaterial-based antennas for a 5.8-GHz Doppler radar. Thus, a double negative index metamaterial structure is designed as a transmitter antenna and a near-zero index medium is integrated with a patch antenna for the receiver. Significant improvements in bandwidth for the transmitter, slight improvements in gain and in directivity for the receiver, and typically size reduction for both antennas are obtained. It is shown that return loss, radiation pattern, and gain measurement results of the newly designed antennas agree well with the simulations for a desired frequency band. The last part of the study is devoted to express the adaptation of the antennas for a low-power radar system whose aim is to reconstruct the velocity of the human, indoor as well as behind the wall, from the shift in the received frequency. The accuracy of the velocity measurements and field test results of the radar with the metamaterial antennas are reported.Article Citation - WoS: 8Citation - Scopus: 9Dynamic Shared Spectrum Allocation for Underlaying Device-To Communications(Institute of Electrical and Electronics Engineers Inc., 2017) Özbek, Berna; Pischella, Mylene; Le Ruyet, DidierThis article provides an overview on spectrum sharing in D2D underlaying communications for 5G and beyond 5G applications. Various spectrum sharing algorithms are summarized within a framework of underlaying D2D communications in cellular networks to increase spectrum efficiency. Dynamic spectrum sharing algorithms in the frequency, power, and spatial dimensions are proposed for underlaying D2D communications with both single antenna and multiple antennas at the base station. Performance evaluations show the effectiveness of the proposed algorithms in terms of average data rate per D2D pair.