Yazar "Sis, Seyit Ahmet" seçeneğine göre listele

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    Effect of the geometry of slots and splits on EMI level of PCBs: A parametric study
    (IEEE, 2021) Sis, Seyit Ahmet; Üstüner, Fatih
    A defect on the reference plane, when crossed over by a signal trace on the signal line, is a primary source for unwanted electromagnetic radiation in printed circuit boards (PCBs). Such a defect either completely cleaves the reference plane into two pieces by means of forming a split between them or partially divides the reference plane by means of forming a slot with a short on at least one end of the defect. This paper presents a detailed parametric study on these defects focusing on how electromagnetic interference (EMI) level varies as a function of geometric parameters. In this regard, first, the width of a slot and a split is systematically varied, and electric field at 3 m away from the PCB is simulated, by keeping the lengths of the slot and split constant. Then, the same simulations are repeated by keeping the width constant and varying the length of the defect. Simulation results show that the length of the defect is an ultimate determinative parameter in the radiation characteristics of the defect. The measurement results for two PCBs; one with a slot and another with a split on the ground plane are also presented.
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    EMI reducing interdigital slot on reference planes of the PCBs
    (IEEE, 2021) Sis, Seyit Ahmet; Üstüner, Fatih; Demirel, Ekrem
    In some very low noise mixed-signal circuits, designers may use intentional slots in order to create a better isolation between a noisy digital ground and a very quiet analog ground, especially in low-frequency applications (<1 MHz) when the current spread in the return plane may interfere with the quiet analog ground. Traces on the signal planes, crossing over these slots, are well-known sources for electromagnetic interference (EMI) due to discontinuities on the return current path. This article presents a novel interdigital slot structure used in the reference planes. The interdigital structure increases the coupling and, hence, provides a low impedance path for the return current of the signal line. This, in return, significantly reduces the radiated emission level in the printed circuit boards (PCBs). Furthermore, due to the periodic nature of transmission lines and the slow-wave effect provided by the interdigital structure, the periodically repeating resonance frequencies of the interdigital defect can be tuned by simply changing the geometric parameters such as digit length and the number of digits. It is shown that the electromagnetic radiation from these slots exhibits peak levels at these antiresonance frequencies, which are also the transmission zeros of the circuit. Conversely, radiation levels are minimized at passbands, where a good signal transmission is achieved. Therefore, this relationship would allow designers to tune the slot length to minimize radiation at the frequency of the signal passing through the trace. Four PCBs with three different-size interdigital structures and a traditional slot structure are first simulated and then fabricated. Well-agreed simulation and measurement results show that the EMI is suppressed by as much as 30 dB within the frequency range of 250MHz–1 GHz. The radiation peaks and dips match with the S21 minima (transmission zeros) and maxima, respectively, in measurement results as well.
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    EMI reduction in multilayer PCBs using planar interdigital slot structures on the reference planes
    (Institute of Electrical and Electronics Engineers Inc., 2022) Baghel, Lalit Kumar; Sis, Seyit Ahmet; Ustuner, Fatih; Kumar, Suman
    In mixed-signal circuits, the return currents of sensitive analog and noisy digital signals must be carefully isolated in order to protect the integrity of the analog signals. To address this issue, a common approach is to utilize slots on the reference plane between digital and analog circuits. However, the slots so created cause the discontinuity in the return current path for a signal passing over these slots which causes unintentional radiation and results in unwanted electromagnetic interference (EMI). In this regard, we propose the planar interdigital slot structures for use in reference planes of multilayer PCBs in order to provide a low impedance path for return current. The interdigital structure alleviates the return current path discontinuity and hence reduces the unintentional radiation. In addition to this, a relationship between radiated emission and transmission response is obtained, allowing the designer to tune the slot parameters to minimize radiation at the signal frequency. PCBs with different size planar interdigital slot structures are simulated in Ansys HFSS and is found that the longer digit length corresponds to better EMI reduction, especially at higher frequencies.
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    Revisiting mode conversion between transmission lines for wide-band modeling of defected ground structures
    (İstanbul Ticaret Üniversitesi, 2023) Sis, Seyit Ahmet; Üstüner, Fatih
    This paper presents a wide-band transmission line model for defected ground structures (DGSs) based on a mode-conversion between microstrip- and slot-lines. The defects on the ground plane are modeled as short- or open-ended transmission lines (TLs) with slot-line characteristics. The transition between microstrip line and ground defect is modeled with interdependent voltage and current sources, of which the first one is placed in series with the microstrip line, and the latter in-shunt with the slot lines, respectively. A complete set of geometry-dependent analytical expressions for the ABCD parameter of a two-port microstrip line crossing over the defected structure is provided. Therefore, the proposed model can be readily integrated into computer-aided design programs. The model’s accuracy is verified in various defect shapes by comparing its results with those from HFSS simulations and measurements.