Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Citation - WoS: 7Citation - Scopus: 8Implementation and Experimental Verifications of Microstrip Antennas for Angular Scanning of a Doppler Radar(Elsevier, 2019) Karatay, Anıl; Orcan, Durmuş; Özkal, Ceren; Yaman, FatihThe aim of this study is to improve operational capabilities and range of the MIT-Coffee Can Doppler radar via aperture coupled Vivaldi type transmitter antenna, patch array receiver antenna, and an unequal power divider. Accordingly, a mechanical angular scanning feature for tracking multi-targets and the system integration of lightweight microstrip structures are realized for the radar. A narrow beamwidth in the receiver and a well impedance matching on the overall system to reduce return losses are achieved for the considered application. Good agreements between simulations and measurements for the fabricated antennas/divider and a successful integration of the antennas to the existing system for finding a moving target angular location is reported. It is shown that through wall identification and target velocity at scanned regions can be obtained with the proposed hardware configuration. Simulation results of antenna parameters for various number of array elements are listed which could be a useful tool for different engineering applications. (C) 2019 Elsevier GmbH. All rights reserved.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: 3Citation - Scopus: 3Inhomogeneity Reconstructions in Tendon Ducts Via Boundary Integral Equations(Elsevier Ltd., 2014) Yaman, Fatih; Weiland, Thomas W.In this study, as an alternative to the formerly presented investigations, Newton-type numerical algorithms are proposed to find location and shape of an air void inside of a tendon duct and to identify gathered metallic bars in a concrete column. The simulated structures are illuminated by four acoustic sources at a fixed frequency such that the scattered field is measured in a near-field region at 128 points. According to the nature of physical problems, the Dirichlet boundary condition is employed to model air-filled cavities and transmission conditions are assumed for metallic objects. Additionally, conductive boundary conditions are suggested for a more realistic representation of the inhomogeneities for the rusty metallic skin of the duct. Potential approaches are used to derive boundary integral equations. The proper treatment of the ill-conditioned equations is established via Tikhonov regularization. Applicability of the proposed inversion algorithms is tested with realistic parameters for different scenarios using noisy scattered field data and accurate numerical results are presented at 10 kHz for the unknown physical properties of the duct's skin.