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Öğe Case study of a radiated susceptibility problem leading to a TVS diode thermal runaway(IEEE, 2021) Üstüner, Fatih; Demirel, Ekrem; Çitkaya, A. Yasin; Mersin, Mücahid T.; Çoşar, ÇoşkunDuring the radiated susceptibility test of an equipment, the thermal runaway of a circuit element (TVS diode) is observed. In this work, the case is systematically investigated to understand how this physical hazard has occurred. By modeling and simulation, the parametric analysis of the induced voltage on the TVS diode has been carried out. Possible solutions are proposed and analyzed. The capacitive filtering solution proves itself both in terms of performance and application easiness point of view.Öğe Effect of the geometry of slots and splits on EMI level of PCBs: A parametric study(IEEE, 2021) Sis, Seyit Ahmet; Üstüner, FatihA 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.Öğe EMI reducing interdigital slot on reference planes of the PCBs(IEEE, 2021) Sis, Seyit Ahmet; Üstüner, Fatih; Demirel, EkremIn 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.Öğe Experimental Comparison of Integrated Circuit Mach-Zehnder Interferometers for Different Types of Output Combiners(Institute of Electrical and Electronics Engineers, 2023) Üstüner, Fatih; Ölçer, İbrahimIn this work, silicon photonic integrated circuit Mach-Zehnder interferometers are evaluated from the output coupler point of view. Simulated results and analytical evaluations are presented to support the design choices. The experimental data is compared against the simulations. The use of correct simulation models is emphasized. The experimental results show that the best overall performance is demonstrated by the MZI configuration with adiabatic coupler. The broadband directional coupler has also good performance. The worst performance is demonstrated by the ordinary directional coupler.Öğe Performance Assessment of Different Cable Shield Terminations under Electromagnetic Field Coupling(Institute of Electrical and Electronics Engineers Inc., 2023) Dikbaş, Elifnur; Üstüner, FatihShielded cables are used to protect the equipment from outside electromagnetic interference (EMI). The integrity of shielding is of paramount importance to obtain maximum performance from these cables. On the other hand, different types of cable shield terminations are preferred without rational in practical applications. This study aims to measure and compare the performance of different cable shield termination configurations under electromagnetic coupling. For this purpose, a test setup constructed around a stripline has been used. The test setup has been validated through both the simulation and measurement. Moreover, to verify the test setup, RF (Radio Frequency) cables and connector sets have been used as a golden reference. After obtaining the expected values from the test setup in accordance with the shielding termination tests of the RF cables, tests were carried out on a military grade cable/connector set with different shield termination configurations. The results show the importance of 360 degree shield terminations at both sides.Öğe Revisiting mode conversion between transmission lines for wide-band modeling of defected ground structures(İstanbul Ticaret Üniversitesi, 2023) Sis, Seyit Ahmet; Üstüner, FatihThis 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.
