MF - Bildiri Koleksiyonu | Elektrik-Elektronik Mühendisliği Bölümü / Department of Electrical-Electronics Engineering
Bu koleksiyon için kalıcı URI
Güncel Gönderiler
Öğe Construction of some classes of two-variable lossless ladder networks with simple lumped elements and uniform transmission lines(IEEE, 1998) Sertbaş, Ahmet; Aksen, Ahmet; Yarman, Bekir Sıddık BinboğaIn this paper, explicit two-variable description of some classes of ladder networks of high-pass, bandpass and band-reject types are presented. Up to a certain complexity, for two-element kinds of these type regular structures, explicit expressions describing the twovariable scattering functions are obtained.Öğe Design trade-offs and considerations for improving the PCB current carrying capacity in high power density power electronics applications(IEEE, 2022-03-24) Büyükdeğirmenci, Veysel T.; Kozarva, Ömer F.; Milletsever, Özgür C.; Hava, Ahmet MasumThis paper investigates printed circuit board (PCB) design trade-offs and considerations to maximize the current carrying capacity of traces in PCB-based power electronics applications. Many existing designs rely on methodologies through empirical data presented by the outdated IPC-2152 standard. A design methodology to maximize the utilized PCB area and improve thermal performance is introduced. To assess this methodology, lumped parameter (LP) and finite element (FE) models are developed and computational fluid dynamics (CFD) simulations are carried out. Thermal via placement strategies are investigated and maximum allowable power dissipation on the PCB traces is calculated. Simulations and analyses are experimentally validated on a PCB-based 100kW three-phase three-level inverter. The that results show that the thermal and electrical models discussed in this paper have superior accuracy compared to traditional formulations.Öğe Path loss and RMS delay spread model for VLC-based patient health monitoring system(Institute of Electrical and Electronics Engineers Inc., 2022-05-13) Dönmez, Barış; Miramirkhani, FarshadVisible Light Communication (VLC) emerges as a supplementary technology to ubiquitous Radio Frequency (RF) since VLC meets the very high data rate, very high reliability, and ultra-low latency requirements driven by the trends in beyond-5G communication systems. Since VLC offers a solution to Electromagnetic Interference (EMI) and security problems in hospital environments, it becomes a better alternative for Medical Body Sensor Networks (MBSNs). Nonetheless, user mobility in a 3D environment causes a degradation in channel DC gain that leads to an optical path loss and also affects the time dispersive properties of multipath channels. In our paper, we adopt a ray tracing-based site-specific channel modeling method to characterize VLC-based MBSNs channel parameters. Based on the channel characteristics, we propose statistical models for path loss and Root Mean Square (RMS) delay spread in realistic Intensive Care Unit (ICU) ward and Family-Type Patient Room (FTPR) where user upon which three MBSNs nodes placed walks over extensive realistic random trajectories. The simulation results indicate that both path loss and RMS delay spread follow a log-normal distribution.Öğe Channel modeling and characterization for VLC-based MBSNs impaired by 3D user mobility(IEEE, 2021-11-27) Dönmez, Barış; Miramirkhani, FarshadThis paper focuses on channel modeling and characterization of indoor visible light communication (VLC)-based medical body sensor networks (MBSNs) which establish links between light-emitting diodes (LEDs) and MBSNs nodes couple with photodetectors (PDs) placed on the shoulder (D1), wrist (D2), and ankle (D3) of the mobile user who walks over random trajectories in 3D scenarios of ICU ward and family type patient room. We adopt non-sequential ray-tracing to obtain channel impulse responses (CIRs) and channel characteristics over random trajectories. Based on simulation results, it is observed that channel DC gains exhibit sinusoidal behaviour for D1 and D2 except for D3 (i.e., due to the number of diffuse rays received at D3), as the user approaches and moves away from the luminaries. It is also revealed that a flat fading channel can be modeled if a data rate lower than 7.03 Mbit/s, i.e., sufficient for MBSNs applications, is chosen.Öğe Considerations for inverter topology selection and limitations in active power filtering applications(IEEE, 2022-03-31) Büyükdeğirmenci, Veysel T.; Sözüer, Abdurrahman; Milletsever, Özgür C.; Kozarva, Ömer F.; Öz, Taha; Hava, Ahmet MasumThis paper presents a modular inverter structure utilizing hybrid SiC MOSFET based active neutral point clamped inverter for active power filter (APF) applications. An FPGA-based digital controller is developed. One major factor in APF applications is the harmonic current capability of the system at higher order harmonics. Commercial products often have a derating curve for higher order harmonic ratings. This paper presents a case utilizing SiC MOSFETs to increase the switching frequency and reduce the LCL filter size. The presented approach is shown to extend the harmonic current capability up to twice in comparison with conventional IGBT-based systems.Öğe When to pull data for minimum age penalty(IEEE, 2021-10-18) Yavaşcan, Orhan Tahir; Ceran, Elif Tuğçe; Cakir, Zeynep; Uysal, Elif; Kaya, OnurA communication receiver that wants to pull data from a remote sensor by exploiting wireless energy transfer is considered. The receiver has a long-term average energy budget for this operation, and its goal is to keep the time average of a general age penalty function as small as possible. The channel from the source to the receiver is a two-state (ON/OFF) communication link whose state is IID or Markovian, and known instantaneously by the receiver. Modeling the problem as a constrained Markov decision problem, we obtain a randomized threshold-based decision policy that achieves the minimum possible average age penalty. We determine the optimal time average Age of Information and age violation probabilities by exploiting the optimality of the derived policy.Öğe Comparative performance evaluation of VLC, LTE and WLAN technologies in indoor environments(IEEE, 2021-05-24) Zeshan, Arooba; Karbalayghareh, Mehdi; Miramirkhani, Farshad; Uysal, Murat; Baykaş, TunçerRecent years have seen an exponential rise in the demand for indoor wireless connections that have driven future generation networks to aim for higher data rates with extended coverage and affordable rates. The two most prominent technologies for providing indoor wireless connections, WLAN and LTE, have their limitations and they can not coexist in a single band to form heterogeneous networks (HetNets). Visible light communication (VLC) has seen rapid growth in recent years as it has the capability to seamlessly merge with the existing technologies and provide wireless connections with high data rates. VLC based hybrid indoor network effectively combines the preferences of an end-user with the practicality of implementation. In this work, we investigate specific VLC/WLAN and VLC/LTE hybrid scenarios to perform a detailed analysis on the effect of user mobility on the performance of the system and how the performance of the network (in terms of throughput) can be maximized. The study aims to show how different technologies complement each other in the best and even the worst-case scenarios.Öğe Co-array optimization of CMUT arrays for forward-looking IVUS(IEEE, 2009-09) Tekeş, Coşkun; Karaman, Mustafa; Değertekin, Fahrettin LeventThe ring annular array structure is a preferred configuration for implementing Forward-Looking IVUS (FLIVUS) catheters as it allows for volumetric imaging as well as use of a guidewire at the center. CMUT technology is promising for these arrays especially with the flexibility of locating array elements on the circular donut area efficiently. To take advantage of this flexibility, in this study, we introduce a new co-array sampling strategy that improves imaging performance while keeping the number of firings at a level suitable for real-time imaging. The presented co-array sampling strategy is based on the idea of adjusting the element density of the co-array rings in radial direction to suppress side lobes. In non-uniform sampling of the co-array with a given number of firings, the inter-element distances are adjusted both in radial and angular direction from inner ring to outer ring to fit a given apodization function. To test the imaging performance, we performed numerical simulations of the co-array with non-uniform sampling fitting to the raised-cosine apodization. The simulation results shows that sidelobe level can be reduced more than 10 dB by using non-uniform co-array sampling. This approach does use uniform weighting of all Tx and Rx elements in beamforming, and hence does not cause any SNR loss for apodization.Öğe Power control in the cognitive cooperative multiple access channel(IEEE, 2012) Kaya, Onur; İşleyen, MuratWe extend several encoding and decoding techniques from cooperative communications framework, to a cognitive radio system consisting of a primary user (PU) and a secondary user (SU), sending their messages to a common receiver. Assuming that the transmitters and the receiver have full channel state information (CSI) collected and distributed by the common receiver, and that the SU knows the PU's codebook, the cooperation is obtained by block Markov superposition coding, and backwards decoding, which yield a causal overlay scenario. We formulate two rate optimization problems with the aim of, (i) maximizing the sum rate of the system, and (ii) maximizing the rate of the secondary user. We obtain the optimal power allocations for both cases, and the resulting rate regions. The power controlled cooperation turns out to be especially useful when maximizing the sum rate of the system, as it gives the PU significant rate rewards for allowing the cognitive transmitter to access its resources.Öğe An endoscopie imaging system based on a two-dimensional CMUT array: real-time imaging results(IEEE, 2005) Wygant, Ira O.; Zhuang, Xuefeng; Yeh, David T.; Vaithilingam, Srikant; Nikoozadeh, Amin; Oralkan, Ömer; Ergün, Arif Sanlı; Karaman, Mustafa; Khuri-Yakub, Butrus ThomasReal-time catheter-based ultrasound imaging tools are needed for diagnosis and image-guided procedures. The continued development of these tools is partially limited by the difficulty of fabricating two-dimensional array geometries of piezoelectric transducers. Using capacitive micromachined ultrasonic transducer (CMUT) technology, transducer arrays with widely varying geometries, high frequencies, and wide bandwidths can be fabricated. A volumetric ultrasound imaging system based on a two-dimensional, 16×l6-element, CMUT array is presented. Transducer arrays with operating frequencies ranging from 3 MHz to 7.5 MHz were fabricated for this system. The transducer array including DC bias pads measures 4 mm by 4.7 mm. The transducer elements are connected to flip-chip bond pads on the array back side with 400-?m long through-wafer interconnects. The array is flip-chip bonded to a custom-designed integrated circuit (IC) that comprises the front-end electronics. Integrating the front-end electronics with the transducer array reduces the effects of cable capacitance on the transducer's performance and provides a compact means of connecting to the transducer elements. The front-end IC provides a 27-V pulser and 10-MHz bandwidth amplifier for each element of the array. An FPGA-based data acquisition system is used for control and data acquisition. Output pressure of 230 kPa was measured for the integrated device. A receive sensitivity of 125 mV/kPa was measured at the output of the amplifier. Amplifier output noise at 5 Mhz is 112 nV/?Hz. Volumetric images of a wire phantom and vessel phantom are presented. Volumetric data for a wire phantom was acquired in real-time at 30 frames per second.Öğe A study on RF/microwave tunable inductor topologies(IEEE, 2013) Turgul, Volkan; Nesimoğlu, Tayfun; Yarman, Bekir Sıddık BinboğaRecently, tunable structures gained importance due to frequency agile microwave circuits such as tunable filters, matching networks, amplifiers, etc. that are needed to realize reconfigurable radios. Deploying tunable inductors would increase the flexibility in reconfigurable microwave circuits when used in conjunction with variable capacitors. In this paper we investigate several tunable inductor topologies. Each proposed topology has certain advantages/disadvantages and these are addressed throughout the paper.Öğe Sperm morphology analysis with CNN based algorithms(IEEE Computer Society, 2014-08-29) Şavkay, Osman Levent; Cesur, Evren; Yalçın, Müştak Erhan; Tavşanoğlu, Ahmet VedatIn this paper Morphological Analysis part of our proposed computer-aided sperm analysis system (CASA) is simulated and the results beside the algorithm steps are presented. The morphology analysis is simply dealing with shape of the sperms and extracting the shape characteristics in medical parameters. The characteristics are obtained by image processing algorithms which utilizes Cellular Nanoscale Network (CNN) based and spatial image processing blocks. The following calculation of medical parameters are obtained from the outputs of image processing blocks. The algorithm is so designed to adapt the final SoC architecture such as Xilinx Zynq7000 device.Öğe Transformer-less ladder network design with non-minimum impedance functions(Institute of Electrical and Electronics Engineers Inc., 2019-11) Yıldız, Serkan; Aksen, Ahmet; Yarman, Bekir Sıddık BinboğaIn this study, a new method of design for transformer-less ladders is introduced. It has been shown that, given a non minimum impedance function which includes finite transmission zeros (FTZs) can be synthesized without transformers. The parametric form of non-minimum impedance function is constructed by cascading a dummy Foster part reactance and a minimum part impedances. The synthesis procedure starts with extraction of Foster part then the minimum part. Even the negative inductors are occurred while extracting FTZs as Brune sections it is shown that, all negative elements are eliminated by the positive valued inductors of adjacent Brune sections. If the impedance function has been only composed of a minimum part impedance then it will not possible to obtain this conclusion. Therefore the proposed parametrical construction provides transformer-free ladder network topologies. Real Frequency Technique is incorporated to optimize the realizable impedance over the band of interest. An low pass (LP) design example is presented.Öğe Tel file geometrilerinin sıradüzensel küme bölüntüleme ile spektral kodlaması(IEEE, 2007-09-04) Konur, Umut; Bayazıt, Uluğ; Ateş, Hasan Fehmi; Gürgen, Sadık FikretÇalışmamızda bir dönüşümle elde edilen spektral katsayılar kullanılarak betimlenen tel file geometri bilgisi, katsayılara bütün bit düzlemlerinde en doğru öncelikler atanarak sıradüzensel bir küme bölüntüleme algoritmasıyla aşamalı biçimde kodlanmaktadır. Kullanılan spektral dönüşüm [8]’de önerilmekte ve geometri bilgisinin topolojiden belirlenen birimdik bir doğuray üzerine düşümlenerek katsayıların elde edilmesi ilkesine dayanmaktadır. Kodlamada kullanılan küme bölüntüleme yöntemi, üç ayrı uzamsal koordinata ait farklı katsayıların bitlerine her bit düzleminde doğru önceliği tanımakta ve katsayıların bit düzlemlerindeki sıfırları birleşik kodladığı için dolaylı bit atamasını başararak tamamen gömülü bir yapıyı sağlayabilmektedir. Yaygın düzensiz tel filelerle yapılan deneylerde önerilen yöntemin hız-bozunum başarımı, [8]’deki kodlama yönteminin hız-bozunum başarımına göre açık bir üstünlük sağlamaktadır.Öğe Improving age of information in random access channels(Institute of Electrical and Electronics Engineers Inc., 2020-07) Atabay, Doğa Can; Uysal, Elif; Kaya, OnurWe study Age of Information (AoI) in a random access channel where a number of devices try to send status updates over a common medium. Assuming a time-slotted scenario where multiple transmissions result in collision, we propose a threshold-based lazy version of Slotted ALOHA and derive the time average AoI achieved by this policy. We demonstrate that the average AoI performance of the lazy policy is significantly better than Slotted ALOHA, and close to the ideal round robin benchmark.Öğe Energy and data cooperation in energy harvesting multiple access channel(Institute of Electrical and Electronics Engineers Inc., 2016-08-26) Gürakan, Berk; Şişman, Berrak; Kaya, Onur; Ulukuş, SennurWe consider the energy harvesting two user Gaussian multiple access channel (MAC), where both users harvest energy from nature. The users cooperate at the physical layer (data cooperation) by establishing common messages through overheard signals and then cooperatively sending them. In addition, the users cooperate at the battery level (energy cooperation) by wirelessly transferring energy to each other. We find the jointly optimal offline transmit power and rate allocation policy together with the energy transfer policy that maximizes the departure region. We provide necessary conditions for energy transfer, and prove some properties of the optimal transmit policy, thereby shedding some light on the interplay between energy and data cooperation.Öğe Computer assisted sperm motility analysis implemented on hybrid CPU+FPGA architecture as an intelligent microscope application(IEEE Computer Society, 2016) Şavkay, Osman Levent; Yalçın, Müştak Erhan; Tavşanoğlu, Ahmet VedatIn this paper we present a Computer Assisted Semen Analysis (CASA) system which is designed and implemented on a hybrid CPU+FPGA architecture platform. The sperm motility analysis deals with the dynamics of sperm movements, thus requires video analysis. A 1280x960 pixel, up to 30 fps programmable camera is used and attached to a trinocular microscope and a PC is used as an HMI and for post calculations, data logging and reporting. The proposed system enables real-time image processing and hence a fast analysis environment, which is important for sperm analysis. In this way we achieved a reconfigurable, reprogrammable, adaptable and extendible system, which can be interpreted as an intelligent microscope.Öğe A discussion on spatiotemporal filtering on a third generation real-time cellular neural network processor(IEEE Computer Society, 2016) Yıldız, Nerhun; Cesur, Evren; Tavşanoğlu, Ahmet VedatA third generation Real-Time Cellular Neural Network (CNN) Processor (RTCNNP-v3) is a CNN emulator currently being implemented targeting FPGA devices. Thanks to the frame buffer support of the RTCNNP-v3 it will be possible to store and recall multiple frames which will extend the range of applications that can be implemented with RTCNNP, including spatiotemporal filters. In this paper, the implementation method of a velocity-tuned filter currently being implemented is disclosed with further discussion.Öğe On the way to a third generation real-time cellular neural network processor(IEEE Computer Society, 2016) Yıldız, Nerhun; Cesur, Evren; Tavşanoğlu, Ahmet VedatIn this proceeding, the architecture of a third generation Real-Time Cellular Neural Network (CNN) Processor (RTCNNP-v3) is disclosed, which is a digital CNN emulator to be implemented on an FPGA device. The previous generation emulator, RTCNNP-v2, is the only CNN implementation reported to be capable of processing full-HD 1080p@60 (1080×1920 resolution at 60 Hz frame rate) video images in real-time. However, there are some weaknesses in both the design and implementation of RTCNNP-v2, like the inability to process different parts of the video images in parallel, lack of support for recording and recalling intermediate frames using external memory and it has some jitter issues at computation rates above 200 MHz. All of those issues are addressed in the next architecture of our CNN emulator, RTCNNP-v3, which is being implemented of an FPGA device.Öğe Spectral coding of mesh geometry with a hierarchical set partitioning algorithm(Spie-Int Soc Optical Engineering, 2008) Konur, Umut; Bayazıt, Uluğ; Ateş, Hasan Fehmi; Gürgen, Sadık FikretThis work proposes a progressive mesh geometry coder, which expresses geometry information in terms of spectral coefficients obtained through a transformation and codes these coefficients using a hierarchical set partitioning algorithm that assigns right priorities to those coefficients at all bit planes. The spectral transformation used is the one proposed in [8] where the spectral coefficients are obtained by projecting the mesh geometry on an orthonormal basis determined by mesh topology. The set partitioning method used in coding, treats spectral coefficients belonging to the three spatial coordinates with the right priority at all bit planes and realizes a truly embedded system by achieving implicit bit allocation via joint coding the zeroes of coefficients at the bit planes. The experiments performed on common irregular meshes reveal that the rate-distortion performance of the coder is significantly superior to the coding system proposed in [8].
