Person: Aksoy, Hasan
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Dr. Öğr. Üyesi
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Aksoy
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Hasan
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Hasan AKSOY
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Publication Error Performance of Subsampling Digital Power Estimation for Integrated Receivers(WORLD SCIENTIFIC PUBL CO PTE LTD, 2022) Khaleel, Aymen; Zencir, Ertan; Aksoy, Hasan; Zencir, Ertan; Aksoy, Hasan; Koc University; Turk Hava Kurumu University; Turkish Aeronautical AssociationEstimation of signal power levels at the output of integrated receiver building blocks is a vital function as the block voltage or power gains are set based on sensed power levels to maintain constant levels at block outputs in the receiver chain. RF and IF level real-time gain settings are determined with Automatic Gain Control (AGC) loops. AGC loop circuit topologies are usually based on analog detection circuits. These analog power detection circuits are based on techniques such as envelope detection, and logarithmic amplification usually accompanied by severe accuracy issues such as Process, Voltage and Temperature (PVT) spreads preventing correct gain adjustments. Adopting a dominantly digital approach to detect the signal power would ensure a significant reduction in PVT spreads. This work presents a review of the subsampling digital power estimation to create low power digital power estimations alternative to analog methods. The simulations of the method are applied to an AM and a 64-QAM signal. Simulation results show that the power estimation error is within the acceptable level of +/- 1 dB.Publication Numerical Inverse Laplace Transform Methods for Advection-Diffusion Problems(MDPI AG, 2022-12-01) Farman Ali Shah; Wael Hosny Fouad Aly; Hasan Aksoy; Fahad M. Alotaibi; Ibrahim Mahariq; Aksoy, HasanPartial differential equations arising in engineering and other sciences describe nature adequately in terms of symmetry properties. This article develops a numerical method based on the Laplace transform and the numerical inverse Laplace transform for numerical modeling of diffusion problems. This method transforms the time-dependent problem to a corresponding time-independent inhomogeneous problem by employing the Laplace transform. Then a local radial basis functions method is employed to solve the transformed problem in the Laplace domain. The main feature of the local radial basis functions method is the collocation on overlapping sub-domains of influence instead of on the whole domain, which reduces the size of the collocation matrix; hence, the problem of ill-conditioning in global radial basis functions is resolved. The Laplace transform is used in comparison with a finite difference technique to deal with the time derivative and avoid the effect of the time step on numerical stability and accuracy. However, using the Laplace transform sometimes leads to a solution in the Laplace domain that cannot be converted back into the real domain by analytic methods. Therefore, in such a case, the Laplace transform is inverted numerically. In this investigation, two inversion techniques are utilized; (i) the contour integration method, and (ii) the Stehfest method. Three test problems are used to evaluate the proposed numerical method. The numerical results demonstrate that the proposed method is computationally efficient and highly accurate.Publication Modeling of Heart Rate Variability Using Time-Frequency Representations(Computers, Materials and Continua (Tech Science Press), 2021) Ghaylen Laouini; Ibrahim Mahariq; Thabet Abdeljawad; Hasan Aksoy; Aksoy, HasanPublication Modeling of Heart Rate Variability Using Time-Frequency Representations(Computers, Materials and Continua (Tech Science Press), 2021) Ghaylen Laouini; Ibrahim Mahariq; Thabet Abdeljawad; Hasan Aksoy; Aksoy, Hasan