Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Citation - WoS: 6Citation - Scopus: 6User Selection for Millimeter Wave Non-Uniform Full Dimensional Mimo(IEEE, 2020) Mumtaz, Rao; Gonzalez, Jonathan; Cumalı, İrem; Özbek, BernaThe millimeter wave (mmWave) based full-dimensional (FD) MIMO communication is one of the promising technology to fulfill the demand of high data rate for the sixth generation (6G) services including 6D hologram, haptic and multi-sensory communications. In order to satisfy the requirements of 6G applications, we investigate a non-uniform rectangular array (NURA) structure with FD-MIMO antenna systems for the multiuser mmWave communications. For the dense scenarios where the number of users to be served is high, we propose user selection algorithms for both digital and hybrid transceiver designs in FD-MIMO with NURA for the multiuser mmWave communications. For the digital transceivers, the users are selected based on their channel correlation considering FD-MIMO with NURA structures. For the hybrid transceivers, sequential user and beam selection is performed using the correlation between the beamspace channels in FD-MIMO with NURA case. The superiority of the NURA compared to uniform antenna structure is shown through the performance evaluations in the multiuser mmWave communications. Besides, the sum data rate results and complexity analysis denote the feasibility of the proposed algorithms compared to the joint user and beam selection schemes.Conference Object Citation - WoS: 1Citation - Scopus: 2Size-Reduced Printed Log Periodic Dipole Antenna With Single First Order Semi-Circle Iteration and Feed Point Patches(Institute of Electrical and Electronics Engineers Inc., 2018) Özgönül, Mehmet Can; Seçmen, MustafaThis paper presents the miniaturization and improvement of a printed log periodic dipole antenna (LPDA) by using patches at the feeding point and single first order semicircles. After the design of a conventional printed LPDA on FR4 substrate to cover L-band is performed, patches having 12 mm × 5 mm dimensions are placed to the feed point of the antenna. Although this modification gives same antenna size, it brings considerable increase in the return-loss bandwidth up to 2.25 GHz and higher gain values up to 2 GHz at the expense of decrease in gain at about 2.4 GHz. Afterwards, in order to reduce the total size of the antenna, single semicircles are substituted into the dipole arms, which results in 14% lateral size reduction. Besides, the bandwidth is further improved between 0.9 GHz and 2.4 GHz with better return loss performance, higher gain at 2.4 GHz and lower gain variation.Article Citation - WoS: 32Citation - Scopus: 41Subsectional Tapered Fed Printed Lpda Antenna With a Feeding Point Patch(Institute of Electrical and Electronics Engineers Inc., 2016) Bozdağ, Göksenin; Kuştepeli, AlpIn this letter, a log-periodic dipole array (LPDA) antenna operating between 1.1 and 13.8 GHz with VSWR < 2and an average peak realized gain of 5.2 dB is presented. It is suitable for GPS (L1-L5), PCS, IMT-2000, Bluetooth, WLAN, WiMAX, UWB, and X-band applications. The antenna is designed by introducing a subsectional tapered feedline instead of standard microstrip feeding, which leads to a remarkable lower-frequency performance. The upper-frequency performance of the antenna is improved by adding a feeding point patch. The group delay is also examined for the final design, and maximum 1.5 ns deviation is observed in UWB. By using ordinary and simple dipoles with this modified feedline approach, a superior antenna performance is obtained over a very wide frequency band, and it is validated by the comparison of three fabricated antennas. Additionally, the antenna size is also reduced without using complicated and/or top-loaded dipole structures.Article Citation - WoS: 12Citation - Scopus: 16The Resonant Behavior of the Fibonacci Fractal Tree Antennas(John Wiley and Sons Inc., 2008) Özbakış, Başak; Kuştepeli, AlpAn investigation of a novel fractal tree antenna with the application to two different geometries is presented. The antenna is designed by using the special Fibonacci number sequence which leads to nonuniform branch length ratios to form the fractal tree. This new approach gives better performance, especially in the miniaturization of the antenna, when compared with the conventional designs. The results obtained from the experiments are also compared with the computed ones and there is a very good agreement between the numerical and measured data.