Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Author: search.filters.author.Karatay, AnilHas files: Yes

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  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Homodyne Detection Based Confocal Phase Diffraction Method for Thickness Characterization of Ultra-Thin Dielectric Films Coated on Optical Fibers
    (Elsevier Ltd, 2025) Karatay, Anil; Atac, Enes
    Characterizing the thickness of thin dielectric films is crucial in fiber optic sensor technologies due to their significant impact on sensor performance. However, non-destructive thickness characterization of films in the range of tens of nanometers, particularly on non-planar surfaces, is often a challenging, complex, and tedious process. In addition, the measurements often need highly calibrated devices under the control of specialists. In this paper, we propose a novel, non-destructive, and practical method for characterizing the thickness of ultra-thin (<100 nm) curved transparent dielectric films using homodyne detection of the confocal phase diffraction. The numerical simulations and experimental results show that suppressing stray light improves the influence of thickness information in the diffracted field. This significantly enhances the system's sensitivity to nanometer-scale variations in dielectric film thickness, especially when integrated with a coherent detection scheme. According to the results, the film thickness can be precisely measured within a few nanometers, making it highly significant and promising for cost-effective optical metrology applications.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Spiral-Shaped Dual-Port Microstrip Antenna for 5G/6G Applications With Wideband-To Transition Using Shape-Memory Alloy
    (Iop Publishing Ltd, 2025) Atac, Enes; Karatay, Anil
    We propose a compact, thermally reconfigurable dual-port microstrip antenna featuring a spiral-shaped design and shape-memory alloy (SMA) that enable switching between wideband and narrowband operation for 5G/6G communication systems. The SMA's thermally induced shape-memory behavior allows reconfiguration in response to temperature changes without the need for electronic or optical control circuits, thus avoiding issues such as self-interference problem, high costs, regular maintenance requirements, and durability concerns. In the wideband mode, measured results show that Port 1 covers 4.7-10.5 GHz and Port 2 covers 4.5-8.3 GHz, which closely agrees with simulations. When the SMA is activated by heat, the antenna switches to the narrowband mode, where Port 1 operates at 7.6 and 9.5 GHz, and Port 2 operates at 8.9 GHz. A ground-plane isolation element ensures low coupling between the ports, with the envelope correlation coefficient remaining below 0.1 across all configurations. The antenna reaches a peak gain of 5.2 dBi and maintains consistent performance through repeated switching. By combining spiral-shaped geometry with a responsive smart material, this work presents a novel and efficient approach for designing reconfigurable dual-port antennas suitable for future wireless technologies.
  • Article
    Citation - Scopus: 2
    Mixture-Based Dielectric Permittivity Measurements Through Gallium-Excited Cavities
    (Ieee-inst Electrical Electronics Engineers inc, 2024) Karatay, Anil; Yaman, Fatih
    In dielectric measurements within resonant cavities, analytical perturbation methods encounter limitations, particularly with nonstandard cavity shapes and lossy materials under test (MUTs) having high dielectric constant. In such cases, the demand for iterative techniques to improve accuracy and flexibility is evident, but the efficiency of the existing iterative techniques, relying on numerical electromagnetic solvers, is often compromised, particularly in terms of time. Therefore, we introduce a novel methodology for measuring the permittivity of dielectric materials using liquid mixtures. This novel method employs a rapid iterative technique in which effective permittivity values are reconstructed at each iteration step based on the volume fraction of liquid mixtures, thus eliminating the dependence on time-consuming 3-D numerical solvers. In addition, we aim to achieve dual-band measurements at 2.45 and 5.8 GHz, enhancing precision by separating mode frequencies. Introducing a re-entrant cavity-like structure, we position the first mode at 2.45 GHz and the second at 5.8 GHz, effectively mitigating intermodal crosstalk and ensuring measurement accuracy. Also, for the first time in the literature, determining which mode will be excited in a cavity by the coupler probe made of gallium can be achieved through the displacement of the liquid metal, which enables measurements to be taken exclusively at the desired frequency.