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In three-phase three-wire (3P3W) voltage-source converter (VSC) systems, utilization of filter inductors with deep saturation characteristics is often advantageous due to the improved size, cost, and efficiency. However, with the use of conventional synchronous frame current control methods, the inductor saturation results in significant dynamic performance loss and poor steady-state current waveform quality. This article proposes an inverse dynamic model-based compensation (IDMBC) method to overcome these performance issues. For this purpose, two-phase exact modeling of the 3P3W VSC control system is obtained. Based on the modeling, the inverse system dynamic model of the nonlinear system is obtained and employed such that the nonlinear plant is converted to a virtual linear inductor system for linear current regulators to perform satisfactorily. Further, to control phase currents in the synchronous frame, a two-phase coordinate transformation is proposed. The IDMBC method is tested via dynamic command response and waveform quality simulations and experiments that employ saturable inductors reaching down from full inductance at zero current to 1/9th inductance at full current. The results obtained demonstrate the suitability of the method for 3P3W VSCs employing saturable inductors. Publisher's Version

In this paper, an algorithm to reconstruct one-dimensional impenetrable rough surface from the knowledge of scattering field is presented. The rough surface is considered as locally perturbed and the scattering field data are collected above the roughness in a simple non-magnetic medium considering Neumann boundary condition. First, the surface integral equation constituted via the Neumann boundary condition is solved and scattering field data are observed synthetically. Then, the same surface integral equation together with the data equation are solved in an iterative fashion to reconstruct the surface variation. In the numerical implementation, the so-called ill-posed inverse problem is regularized with Tikhonov method and a least-squares solution is obtained by using Gaussian-type basis function. Finally, numerical examples are carried out to illustrate effectiveness of the method. Publisher's Version Q4 WOS:000722764600001

A convolutional neural network (CNN) based deep learning (DL) technique for electromagnetic imaging of rough surfaces separating two dielectric media is presented. The direct scattering problem is formulated through the conventional integral equations and the synthetic scattered field data is produced by a fast numerical solution technique which is based on Method of Moments (MoM). Two different special CNN architectures are designed and implemented for the solution of the inverse rough surface imaging problem wherein both random and deterministic rough surface profiles can be imaged. It is shown by a comprehensive numerical analysis that the proposed deep-learning (DL) inversion scheme is very effective and robust. Publisher's Version Q1 WOS:000880709700101

In the context of beyond 5G indoor communication systems, visible light communications (VLC) has emerged as a viable supplement for existing radio frequency based systems and as an enabler for high data rate communications. However, the existing indoor VLC systems are limited by detrimental outages caused by fluctuations in the VLC channel gain because of user mobility. In this study, we proposed a tractable path loss model for indoor VLC that reflects the effect of room size and coating material of surfaces. We performed an extensive advanced ray tracing simulation to obtain the channel impulse responses within a room and presented a path loss model as a function of distance, room size, and coating material through curve fitting. In addition, path loss parameters such as the path loss exponent and the standard deviation of the shadowing component were determined. The simulation results indicate that path loss is a linear function of distance, path loss exponent is a function of room size and coating material, and shadowing follows a log normal distribution. Publisher's Version Emerging Sources Citation Index (ESCI) Q4 WOS:000656762700009

In this paper, a convolutional neural network (CNN)-based deep learning (DL) architecture for the solution of an electromagnetic inverse problem related to imaging of the shape of the perfectly electric conducting (PEC) rough surfaces is addressed. The rough surface is illuminated by a plane wave and scattered field data is obtained synthetically through the numerical solution of surface integral equations. An effective CNN-DL architecture is implemented through the modelling of the rough surface variation in terms of convenient spline type base functions. The algorithm is numerically tested with various scenarios including amplitude only data and shown that it is very effective and useful. Publisher's Version Q2 WOS:000836577000001

A new method to design transformer-free low pass (LP) ladder network with improved stop-band suppression performance is introduced. The parametric representation of back-end impedance of LP filter network is established with minimum impedance part and a Foster reactance part. The constructed impedance function is optimized by using real frequency technique. It has been shown that the proposed method provides LP filters which have superior stop-band suppression in comparison with classical transfer function-based filters with same complexity. The synthesis of the LP filter is obtained with the proposed element extraction procedure and resulted with fully realizable network elements in ladder form. An LP filter design and application by employing the proposed technique is provided. The measurement results of the prototyped filter are presented. Publisher's Version Q4 WOS:000621554000001

Vehicular visible light communications (VLC) has emerged as a viable supplement for high speed next-generation vehicle to vehicle (V2V) communication systems. However, performance of a V2V-VLC link is impaired due to nonlinear transfer-characteristics of light emitting diodes (LEDs), and inter-symbol interference (ISI). In this article, a low-complexity least-squares based post-distortion algorithm is formulated over reproducing kernel Hilbert space (RKHS) for a multi-hop V2V-VLC link. The impairments encountered in V2V-VLC channels are mitigated in RKHS by a minimum symbol error-rate post-distorter using a low dimensional approximation of random Fourier features (RFF) (which is a soft approximation of the feature-map to RKHS), that facilitates computationally simple post-distortion under finite memory-budget. The convergence and the BER-performance of the proposed post-distorter is analyzed over realistic V2V VLC channels obtained via ray-tracing. From the analysis, and the presented computer-simulations, the proposed post-distorter is found to exhibit equivalent convergence characteristics and error-rate over reasonable distances, with much lower computational complexity. Publisher's Version

In this paper, a new multiband frequency mapping function is proposed to design multiband filter. The presented mapping function is a generalized form of the sequential low pass to band pass (LPtoBP) transformation. The multiband filter design is based on the application of the frequency mapping function on a LP prototype. The synthesis of the resulting multiband filter is obtained by lumped element resonators. Several examples are presented to validate the proposed design approach. A triple band filter implementation and measurement results are presented. Publisher's Version Q4 WOS:000546752900009

Visible 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. Publisher's Version

This 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. Publisher's Version

This letter addresses a reconstruction algorithm of locally rough inaccessible surface profiles via the knowledge of the scattered field data under the consideration of the impedance boundary condition (IBC). To this aim, first, the synthetic scattered field data are obtained through the solution of the conventional surface integral equation (SIE) written on the rough surface. Then, the same SIE together with the data equation is solved iteratively via Newton's method to obtain the image of the rough surface profile. In the numerical implementation, the nonlinear ill-posed inverse problem is linearized in an iterative fashion via the Newton method and regularized by Tikhonov in the least-squares sense. The feasibility of the algorithm is provided via numerical examples, which shows that the method is effective and promising. Publisher's Version

In this research work, we propose a one-dimensional Convolutional Neural Network (CNN) based biometric identification system that combines speech and ECG modalities. The aim is to find an effective identification strategy while enhancing both the confidence and the performance of the system. In our first approach, we have developed a voting-based ECG and speech fusion system to improve the overall performance compared to the conventional methods. In the second approach, we have developed a robust rejection algorithm to prevent unauthorized access to the fusion system. We also presented a newly developed ECG spike and inconsistent beats removal algorithm to detect and eliminate the problems caused by portable fingertip ECG devices and patient movements. Furthermore, we have achieved a system that can work with only one authorized user by adding a Universal Background Model to our algorithm. In the first approach, the proposed fusion system achieved a 100% accuracy rate for 90 people by taking the average of 3-fold cross-validation. In the second approach, by using 90 people as genuine classes and 26 people as imposter classes, the proposed system achieved 92% accuracy in identifying genuine classes and 96% accuracy in rejecting imposter classes. This research work was supported by Coordination Office for Scientific Research Projects, FMV ISIK University (Project Number: 14A203 ) and Scientific Research Projects Unit, Bursa Technical University (Project Number: 181N14 ). Umit Guz received the B.S. degree in Electronics Engineering from the Istanbul University, College of Engineering, Turkey, in 1994, the M.S. and Ph.D. degrees in Electronics Engineering from the Institute of Science, Istanbul University, Turkey, in 1997 and 2002, respectively. He was awarded a post-doctoral research fellowship by the Scientific and Technological Research Council of Turkey (TUBITAK) in 2006. He was accepted as an international research fellow by the SRI (Stanford Research Institute)-International, Speech Technology and Research (STAR) Laboratory, Menlo Park, CA, USA, in 2006. He was awarded a J. William Fulbright post-doctoral research fellowship, USA, in 2007. He was accepted as an international research fellow by the International Computer Science Institute (ICSI), Speech Group at the University of California at Berkeley, Berkeley, CA, USA, in 2007 and 2008. He worked as an Assistant Professor and an Associate Professor in the Department of Electrical-Electronics Engineering, Engineering Faculty at Isik University, Istanbul, from 2008 to 2013 and from 2013 to 2019, respectively. He has been a full-time professor in the Department of Electrical-Electronics Engineering, Faculty of Engineering and Natural Sciences at Isik University, Sile, Istanbul, Turkey, since 2019. His research interest covers speech processing, automatic speech recognition, natural language processing, machine learning, and bio-signal processing. Publisher's Version

This 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. Publisher's Version

This study is supported in part by TUBITAK grant 119C028, and in part by Turkcell Technology within the framework of 5G and Beyond Joint Graduate Support Programme coordinated by Information and Communication Technologies Authority. A 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. IEEE Control Systems Society Information Theory Society Communication Systems Technical Committee (Performance of Communication Systems Working Group) Publisher's Version WOS:000766966900006

This study presents a new compact design technique for dual band stop (DBS) filter. Analytical formulation of DBS frequency transformation/mapping is derived in terms of parametric representation of band characteristic of DBS filter. The analytical derivation of the transformation function is based on sequential application of classical low pass to band stop (LP to BS) and low pass to band pass (LP to BP) transformations. Assigned band characteristic of DBS filter can be achieved by applying the proposed transformation function on an LP prototype network. The explicit network topologies for DBS reactance mapping are presented. Several numerical examples are provided to validate the proposed mapping function. An implantation example of DBS filter for GSM900 and GSM1800/UMTS bands is given. Mixed element realisation of the designed filter and measurement results of the design are presented. Publisher's Version Q4 WOS:000526387300007

While age of Information (AoI) has gained importance as a metric characterizing the freshness of information in information-update systems and time-critical applications, most previous studies on AoI have been theoretical. In this chapter, we compile a set of recent works reporting AoI measurements in real-life networks and experimental testbeds, and investigating practical issues such as synchronization, the role of various transport layer protocols, congestion control mechanisms, application of machine learning for adaptation to network conditions, and device related bottlenecks such as limited processing power.

Recent 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. Publisher's Version WOS:000892556200021

Visible light communications (VLC) has emerged as a high-speed, low-cost, and green supplement for the existing radio frequency (RF) based infrastructures. However, the performance of VLC based systems is found to degrade significantly due to detrimental outages caused by non-negligible variations in the VLC channel-gain, that are jointly induced by radial user-mobility and random photodetector-orientation (together designated as 3D mobility in this letter). In addition to the 3D user-mobility mentioned above, the performance of VLC based systems is further limited by imperfect channel-state information (CSI). Such degradations in the VLC-link caused by the aforementioned factors necessitate the quantification of performance-metrics for further benchmarking/receiver-design. In this work, an analytical expression for bit-error rate (BER) is derived for a single LED indoor VLC system considering the radial user-mobility, random receiver orientation, and imperfect CSI altogether. Further, the derived BER expressions are validated using computer-simulations using typical VLC channel models from the literature. A close agreement between the analytical and the simulated BER is observed, which verifies the accuracy of the presented analysis. Publisher's Version

Visible light communication (VLC) has emerged as a viable complement to traditional radio frequency (RF) based systems and as an enabler for high data rate communications for beyond-5G (B5G) indoor communication systems. In particular, the emergence of new B5G-based applications with quality of service (QoS) requirements and massive connectivity has recently led to research on the required service-levels and the development of improved physical (PHY) layer methods. As part of recent VLC standards development activities, the IEEE has formed the 802.11bb “Light Communications (LC) for Wireless Local Area Networking” standardization group. This paper investigates the network requirements of 5G indoor services such as virtual reality (VR) and high-definition (HD) video for residential environments using VLC. In this paper, we consider such typical VLC scenarios with additional impairments such as light-emitting diode (LED) nonlinearity and imperfect channel feedback, and propose hyperparameter-free mitigation techniques using Reproducing Kernel Hilbert Space (RKHS) methods. In this context, we also propose using a direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM)-based adaptive VLC transmission method that uses precomputed bit error rate (BER) expressions for these RKHS-based detection methods and performs adaptive BER-based modulation-order switching. Simulations of channel impulse responses (CIRs) show that the adaptive transmission method provides significantly improved error rate performance, which makes it promising for high data rate VLC-based 5G indoor services. This work was supported by the Generalitat de Catalunya, Spain [grant number 2017 SGR 1195 ] and the national program on equipment and scientific and technical infrastructure under the European Regional Development Fund (FEDER) [grant number EQC2018-005257-P ]. Publisher's Version

Reports on the activities of CASS chapters. Publisher's Version

Reports on CASS chapter activities in Central America and Mexico. Publisher's Version

Visible light communication (VLC) has been proposed as an alternative or complementary technology to radio frequency vehicular communications. Front and back vehicle lights can serve as wireless transmitters making VLC a natural vehicular connectivity solution. In this paper, we evaluate the performance limits of vehicular VLC systems. First, we use non-sequential ray tracing to obtain the channel impulse responses (CIRs) for vehicle-to-vehicle (V2V) link in various weather conditions. Based on these CIRs, we present a closed-form path loss expression which builds upon the summation of geometrical loss and attenuation loss and takes into account asymmetrical patterns of vehicle light sources and geometry of V2V transmission. The proposed expression is an explicit function of link distance, lateral shift between two vehicles, weather type (quantified by the extinction coefficient), transmitter beam divergence angle and receiver aperture diameter. Then, we utilize this expression to determine the maximum achievable link distance of V2V systems for clear, rainy and foggy weather conditions while ensuring a targeted bit error rate. The work of H. B. Eldeeb was supported by the Horizon 2020 MSC ITN (VISION) under Grant 764461. The work of M. Uysal was supported by the Turkish Scientific and Research Council (TUBITAK) under Grant 215E311. The author Sadiq M. Sait would like to thank KFUPM for support. This article was presented in part at IEEE Vehicular Technology Conference, 2018 and in part at IEEEWireless Communications and Networking Conference, 2019. The review of this article was coordinated by Prof. F. Lavagetto Publisher's Version

Fast simplified real frequency technique (FSRFT) is a numerical solver used to solve microwave broadband double-matching (DM) circuit design problems in a much faster and effective manner. Recently, it has been reported that an FSRFT based Matlab code can complete the design of a order lowpass lumped element double matching network to match a given generator and load impedance within an optimization time of only 0.6 seconds, a 47 fold less time than that of the same design done using the classical simplified real frequency technique (SRFT). FSRFT owes this superior speed performance to the fact that it tracks only (system unknowns plus 1) number of passband extremum points selected from among the number of gain data (). This work introduces a simple numerical technique called PED (passband extremums determination technique) to be used in determination of these passband extremum points (PEs). An exemplary order microwave bandpass DM circuit design using FSRFT based Matlab (of Mathworks Inc.) code and the simulation of this design via MWO (of AWR Corp.) has yielded the same circuit performance with an exact agreement. Thus, FSRFT, equipped with the PED, newly proposed hereby, might be used as a powerful solver in designing broadband circuits in many fields such as RF/microwave, radar, and communications.

Minayi, Elham (Dogus Author) A new kind of metamutator, namely “Current Inverting Metamutator”, its realizations using different types of active blocks and some of its applications like voltage-mode universal biquadratic filter with three input and one output terminals are presented. The proposed circuits can realize all standard filters, namely, low-pass, band-pass, high-pass, notch and all-pass without passive component matching conditions. The proposed circuit offers the features of using grounded capacitors and orthogonal controllability of angular frequency and quality factor. Then a novel realization of metamutator with one active device, additive and differential IC (AD-IC) is proposed and implemented with twelve transistors only. The metamutator with AD-IC has the advantages: (1) of creating new realizations of memristors, capacitance multipliers, inductor simulators, frequency dependent negative resistors which can be used to make IC active filters, (2) less is the number (only one) of active devices, less is the amount of disparity, (3) no need to match passive component values.

In this research work, we present a newly fingertip electrocardiogram (ECG) data acquisition device capable of recording the lead-1 ECG signal through the right- and left-hand thumb fingers. The proposed device is high-sensitive, dry-contact, portable, user-friendly, inexpensive, and does not require using conventional components which are cumbersome and irritating such as wet adhesive Ag/AgCl electrodes. One of the other advantages of this device is to make it possible to record and use the lead-1 ECG signal easily in any condition and anywhere incorporating with any platform to use for advanced applications such as biometric recognition and clinical diagnostics. Furthermore, we proposed a biometric identification method based on combining autocorrelation and discrete cosine transform-based features, cepstral features, and QRS beat information. The proposed method was evaluated on three fingertip ECG signal databases recorded by utilizing the proposed device. The experimental results demonstrate that the proposed biometric identification method achieves person recognition rate values of 100% (30 out of 30), 100% (45 out of 45), and 98.33% (59 out of 60) for 30, 45, and 60 subjects, respectively. This research work was supported by Coordination Office for Scientific Research Projects, FMV ISIK University (Project Number: 14A203). Patent application of the newly proposed data acquisition device is pending status with the patent application number 2016/18442 at the Turkish Patent Institute. The authors thank the anonymous reviewers for their useful and valuable comments on an earlier version of this paper Publisher's Version

Non-sequential ray tracing simulations are commonly employed to model underwater visible light communication (VLC) channels. The accuracy of such simulations highly depends on how well the optical properties of water (i.e., absorption and scattering) as well as scattering phase function (SPF) are modeled in the simulation. Existing empirical models are only a function of chlorophyll concentration and particle composition and are independent of refractive index, size and concentration of particles. In this paper, we carry out an underwater VLC channel modeling study using the Mie SPF which provides a full description of the scattering from phytoplankton particles which dominate the optical properties of most oceanic waters. We obtain the channel impulse response (CIR) based on an extensive non-sequential ray tracing study and calculate the fundamental channel parameters such as channel gain and delay spread. Comparison of CIRs reveals out that deployment of simplified SPF models results in the overestimation of path loss with respect to Mie SPF. Our results clearly demonstrate the importance of selecting realistic SPF models for an accurate underwater VLC channel modeling. While highlighting the channel models, we discuss adaptive modulation technique to maximize the data rate under the constraint of a targeted bit error rate. Besides, the maximum achievable distance is also determined both in terms of analytical guarantees and computer simulations. The results reveal that larger transmission distances can be achieved through Mie SPF channel model. Publisher's Version

This work presents a new low-loss active inductor whose self-resonance frequency and quality factor parameters can be adjusted independently from each other. In order to achieve this property, a new input topology has been employed which consists of cascode structure with a diode connected transistor. Furthermore, the proposed input topology makes the device robust in terms of its performance over variation in process, voltage and temperature. Additionally, RC feedback is used to cancel series-loss resistance of the active inductor, which allows self-resonant enhancement as well. Schematic and post-layout simulation results show the theoretical validity of the design. To validate the design feasibility for process, voltage and temperature changes, Monte Carlo and temperature analysis are done. Suggested structure shows inductor behavior in the frequency range of 0.3–11.3 GHz. Maximum quality factor is obtained as high as 2.1k at 5.9 GHz. Total power consumption is as low as 1 mW with 1.8 V power supply. Publisher's Version

We 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. This work was funded in part by Huawei and by TUBITAK Grant 117E215. Publisher's Version

PubMed ID: 32114913 Visible light communication (VLC) allows the dual use of light-emitting diodes (LEDs) for wireless communication purposes in addition to their primary purpose of illumination. As in any other communication system, realistic channel modelling is a key for VLC system design, analysis and testing. In this paper, we present a comprehensive survey of indoor VLC channel models. In order to set the background, we start with an overview of infrared (IR) channel modelling, which has received much attention in the past, and highlight the differences between visible and IR optical bands. In the light of these, we present a comparative discussion of existing VLC channel modelling studies and point out the relevant advantages and disadvantages. Then, we provide a detailed description of a site-specific channel modelling approach based on non-sequential ray tracing that precisely captures the optical propagation characteristics of a given indoor environment. We further present channel models for representative deployment scenarios developed through this approach that were adopted by the Institute of Electrical and Electronics Engineering (IEEE) as reference channel models. Finally, we consider mobile VLC scenarios and investigate the effect of receiver location and rotation for a mobile indoor user. This article is part of the theme issue ‘Optical wireless communication’. Funding. This work was supported by the Turkish Scientific and Research Council (TUBITAK) under grant no. 215E311 Publisher's Version

Voltage Inverting Metamutator (VIM) and Current. Voltage Inverting Metamutator (VIM) and Current Inverting Metamutator (CIM) recently introduced in [1] were defined, respectively, with polarities shown in Fig. 1 and relations (1) and (2). However, a careful examination reveals that there is no difference between VIM and CIM of Fig. 1b as changing the reference directions of vn and in in VIM gives CIM as shown in Figs. 1b and 2. So the 4-ports in Fig. 1a, b are the same. The CIM as given by Fig. 2, with the same reference directions as those of VIM, and defining relation (2) is an entirely different 4-port. In fact, their circuit level realizations are respectively given in Fig. 3a, b. Publisher's Version

In 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. Publisher's Version WOS:000552654100098

The introduction of light emitting diodes (LED) in automotive exterior lighting systems provides opportunities to develop viable alternatives to conventional communication and sensing technologies. Most of the advanced driver-assist and autonomous vehicle technologies are based on Radio Detection and Ranging (RADAR) or Light Detection and Ranging (LiDAR) systems that use radio frequency or laser signals, respectively. While reliable and real-time information on vehicle speeds is critical for traffic operations management and autonomous vehicles safety, RADAR or LiDAR systems have some deficiencies especially in curved road scenarios where the incidence angle is rapidly varying. In this paper, we propose a novel speed estimation system so-called the Visible Light Detection and Ranging (ViLDAR) that builds upon sensing visible light variation of the vehicle's headlamp. We determine the accuracy of the proposed speed estimator in straight and curved road scenarios. We further present how the algorithm design parameters and the channel noise level affect the speed estimation accuracy. For wide incidence angles, the simulation results show that the ViLDAR outperforms RADAR/LiDAR systems in both straight and curved road scenarios. Publisher's Version

Termination transformation theorem (TTT) proposed in this work transforms a doubly complex terminated microwave power transfer network (PTN) to an equivalent doubly resistively terminated termination transformed network (TTN) which is essentially a filter network. In this work, the transducer power gain (TPG) formula, Tgen, based on S and transmission (ABCD) parameters for the PTN have been restudied from the classical literature. Then, a new TPG formula, Tgen1, based on the newly proposed TTT has been derived using the transformed TTN network. To be able to show the validity of the proposed TTT, the newly derived TPG formula Tgen1 and the classical TPG formula Tgen have been computed within the scope of an example PTN design. The theorem has been proved mathematically, and experimentally as well with the aid of a Matlab code. The performance plots yielded from the Matlab code have clearly shown that both TPG formulae, i.e., Tgen and Tgen1, are in complete agreement with each other. In that sense, the proposed TTT might be considered as an alternative and helpful technique to be used in microwave engineering. Publisher's Version Q4 WOS:000627368200011

The author presents his gratitudes to Isik University for the encouragement of him to present the paper in the conference of PGSRET-2019 and also the financial support of him. Design and simulation of a microwave wideband microstrip unit element bandpass matching network is presented, potential use might be a broadband WPT (microwave wireless power transfer) application in X-band frequencies (8-12 GHz). The source of the main energy can be wind, fossil, tidal, solar, nuclear, hydro etc. and the main energy can be converted from DC to microwave energy which then can be transmitted via the proposed WPT circuit towards a few or a network of a multiple microwave harvester receivers located at a near or far field from the main source. In the work, a bandpass matching network (BPMN) composed of microstrip "unit elements (UEs)" is designed to operate along the whole X-band (8-12 GHz). Designed BPMN is excited by an X-band commercial PA (power amplifier) MMIC (monolithic microwave integrated circuit) packaged chip, and it is loaded by an X-band microstrip patch antenna. A bond wire soldered between the RF output pad of MMIC chip and the input pad of the BPMN has an equivalent LC parasitic impedance assumed to be the generator complex impedance that must be compensated in a typical matching problem. SRFT (simplified real frequency technique) is used in the design of the matching network that compensates the effect of bond wire and very good agreement found between the theoretical design and simulations done in MWO (AWR). Int Islam Univ Gazi Univ, Tech Fac Int Islam Univ, Fac Engn & Technol Publisher's Version WOS:000611393300021

The work of Hossien B. Eldeeb was supported by the European Horizon 2020 MSC ITN (VISION) under Grant 764461. The work of M. Uysal was supported by the Turkish Scientific and Research CouYncil (TUBITAK) under Grant 215E311. The increasing adoption of LEDs in exterior automotive lighting makes visible light communication (VLC) a natural solution for vehicular networking. In this paper, we consider a vehicle-to-vehicle link and propose a path loss expression as a function of distance and different weather conditions. We conduct ray tracing simulations and verify the accuracy of proposed expression. We further use this expression to derive the achievable transmission distance for a targeted data rate while satisfying a given value of bit error rate. Numerical results are presented to demonstrate the achievable distances for single and dual photodetector deployment cases. Publisher's Version WOS:000684562200041

Aliasing and spectral leakage are artifacts of sampling and rectangular windowing, respectively, whose manifestations are noticed in both the spatial and frequency domains. This paper aims to provide a classroom example which enables the recognition and mathematical interpretation of such phenomena. Publisher's Version

In this work, an efficient low bit rate image coding/compression method based on the quadtree-based partitioned universally classified energy and pattern building blocks (QB-UCEPB) is introduced. The proposed method combines low bit rate robustness and variable-sized quantization benefits of the well-known classified energy and pattern blocks (CEPB) method and quadtree-based (QB) partitioning technique, respectively. In the new method, first, the QB-UCEPB is constructed in the form of variable length block size thanks to the quadtree-based partitioning rather than fixed block size partitioning which was employed in the conventional CEPB method. The QB-UCEPB is then placed to the transmitter side as well as receiver side of the communication channel as a universal codebook manner. Every quadtree-based partitioned block of the input image is encoded using three quantities: image block scaling coefficient, the index number of the QB-UCEB and the index number of the QB-UCPB. These quantities are sent from the transmitter part to the receiver part through the communication channel. Then, the quadtree-based partitioned input image blocks are reconstructed in the receiver part using a decoding algorithm, which exploits the mathematical model that is proposed. Experimental results show that using the new method, the computational complexity of the classical CEPB is substantially reduced. Furthermore, higher compression ratios, PSNR and SSIM levels are achieved even at low bit rates compared to the classical CEPB and conventional methods such as SPIHT, EZW and JPEG2000 This research work was supported by the Coordination Office for Scientific Research Projects, FMV ISIK University (Project Number: 10B301) Publisher's Version

In the context of beyond-5G indoor communication systems, visible light communication (VLC) has emerged as a viable supplement for existing RF-based systems and as an enabler for high datarate communications. However, the existing indoor VLC systems are limited by detrimental outages caused by fluctuations in the VLC channel-gain due to user-mobility. Furthermore, the nonlinear characteristics of the light-emitting diode (LED) degrade the performance of VLC systems in the highpower regime by warping the input constellation. Additional performance-limits are introduced by inter-symbol interference (ISI) due to finite modulation-bandwidth of LEDs, and reflections from walls. In this paper, a random Fourier feature (RFF) based post-distorter is considered for mitigating the LED nonlinearity, and relevant expressions for the signal to noise ratio (SNR) are derived for a direct current biased optical orthogonal frequency division multiplexing (DCO-OFDM) system. Based on the derived expressions for SNR, the effects of user-mobility and ISI are mitigated by a DCO-OFDM based adaptive VLC transmission technique, which varies the transmission-rate/modulation-order under a specified error-rate constraint. Simulations are presented over channels obtained by ray-tracing, which indicates that the proposed algorithm achieves superior data-rates with a significantly lower error-rate. Publisher's Version

It is shown that an (M× N)-node planar resistive grid can be decomposed into two sub-grids; one made up of M N-node horizontal and the other of N M-node vertical linear resistive grids which corresponds to decomposing its nodal conductance matrix (NCM) into the Kronecker sum of the NCMs of horizontal and vertical linear grids. This enables the analytical expressions of the eigenvalues and eigenvectors of the NCMs of the sub-grids as well as those of the planar resistive grid to be expressed in terms of those of the two linear grids, whose analytical expressions are well known. For a Cellular Neural Network (CNN) Gabor-type filter (GTF) we define generalized nodal conductance matrices (GNCMs) that correspond to the NCMs of the resistive sub-grids, show that each Kronecker decomposition has a counterpart in CNN GTF and prove that each GNCM, its counterpart NCM and the corresponding temporal state matrices are related through unitary diagonal similarity transformations. Consequently, we prove that the eigenvalues of the temporal state matrix of a spatial band-pass CNN GTF are the same as those of its counterpart spatial low-pass CNN image filter, hence their temporal transient behaviors are similar in settling to a forced response. Publisher's Version

Assessment of damage caused by a disaster is significant for coordinating emergency response teams and planning emergency aid. In this letter, a robust method for rapid building damage assessment is proposed using pre- and postevent EO images and building footprints. The method uses a local self-similarity descriptor (SSD) for change detection in buildings, which is shown to be robust against variations in global illumination and small local deformations. The use of building footprints helps reduce the false alarms due to changes in nonbuilding areas. Footprint is also used to differentiate small and large buildings, extract the boundary region of a building, and adapt the descriptor computation accordingly. It is shown that the adaptive SSD provides a more accurate measure of local damage on the building. The 2010 Haiti Earthquake and Typhoon Haiyan 2013 Philippines are analyzed with the proposed method, and 75/82% true positive rate and 25/15% false positive rate are obtained for detection of collapsed buildings with respect to the ground truth data of UNITAR/UNOSAT and HOT. This work was supported in part by the Republic of Turkey Prime Ministry Disaster and Emergency Management Presidency (AFAD) and TUBITAK BILGEM under Grant B740-G585000 Publisher's Version

Yıldız, Merih (Dogus Author) -- Minaei, Shahram (Dogus Author) NMOS based circuit realizations of a sinusoidal quadrature oscillator, a transconductance, a transimpedance amplifier are presented. All the circuits are constructed with a voltage-mode “Metamutator” consisting of an analog adder and a subtractor which is one of its possible realizations. The most important feature of the proposed circuits is their extremely simple structures containing only twelve NMOS transistors (six for adder, six for subtractor). Another significant advantage of the proposed circuits is that no external passive element is needed for the oscillator and only one resistor is used for each amplifier circuit; a variable resistor can provide gain adjustability. The post-layout simulations of all the proposed circuits have been executed using TSMC 0.25 µm process parameters with ±1.25 V power supply voltage.

Improved image processing and developing technologies are rapidly expanding the application areas of image processing systems. In recent years, pedestrian detection systems have become one of the major safety technologies used in the automotive industry. This paper presents an optimised real-time pedestrian detection system using an FPGA-CPU based hybrid design. The histograms of oriented gradients (HOG) algorithm, which is extensively used for feature extraction in pedestrian detection applications, was implemented on a low-end FPGA. In the study, the original HOG descriptors are designed in low complexity without sacrificing performance. The obtained features were classified on a low-power single board computer with support vector machine (SVM). Tests with the INRIA pedestrian database show that the proposed model has high potential for use as a real-time low-cost pedestrian detection system in practice. Publisher's Version

Semantic segmentation (i.e. image parsing) aims to annotate each image pixel with its corresponding semantic class label. Spatially consistent labeling of the image requires an accurate description and modeling of the local contextual information. Segmentation result is typically improved by Markov Random Field (MRF) optimization on the initial labels. However this improvement is limited by the accuracy of initial result and how the contextual neighborhood is defined. In this paper, we develop generalized and flexible contextual models for segmentation neighborhoods in order to improve parsing accuracy. Instead of using a fixed segmentation and neighborhood definition, we explore various contextual models for fusion of complementary information available in alternative segmentations of the same image. In other words, we propose a novel MRF framework that describes and optimizes the contextual dependencies between multiple segmentations. Simulation results on two common datasets demonstrate significant improvement in parsing accuracy over the baseline approaches., 8 pages and 3 figure, accepted to Pattern Recognition Letters, Elsevier

Minayi, Elham (Dogus Author) -- Conference full title: 25th IEEE International Conference on Electronics Circuits and Systems, ICECS 2018; Bordeaux; France; 9 December 2018 through 12 December 2018. Using the recently developed Add-Differentiate 5-terminal Integrated Circuit, AD-IC (which possess 12 CMOS transistors only), augmented with two diodes, a new rectifier configuration is presented. Transistor level circuit and its layout are provided and the rectifier is simulated with parameters extracted from the layout showing very good conformity with desired rectifier behavior. Finally, a table of comparison of the proposed rectifier with fourteen others, existing in the literature, is included to conclude the paper.

The purpose of this note is (i) to point to a reference missing in the paper (Mayo-Maldonado et al., 2018) and (ii) to show that some of its content is covered in a more general setting by the results in that reference (Goknar, 1972). Publisher's Version Q3 WOS:000449785700001

In this study, a multiband matching network design technique is presented. Mixed lumped and distributed elements are used to form Transducer Power Gain (TPG) of the matching network. Finite frequency transmission zeros are included in final design to create multiband TPG characteristic. Foster resonance sections are used to realize finite transmission zeros. Approximate distributed model of Foster resonance section is incorporated in design. An illustrative dual band matching network design for a PIFA antenna is presented. It has been shown that using distributed equivalent models of Foster resonance sections in mixed matching network design provides satisfactory TPG levels at intended frequency bands. Publisher's Version WOS:000458427500050

In this paper, design of a real-time video frame differentiator based on an external memory interface is proposed. Furthermore, implementation and simulation processes of the design is discussed. The proposed design is capable of differentiating video frames over time, up to full-HD resolution at 60 Hz frame rate. An external SDRAM memory unit is used within the proposed design and drived by a memory interface. In order to improve the flexibility of the architecture, video resolution, video buffer size on memory and burst size of the memory interface are designed to be user defined and configurable. Publisher's Version

Implementation and demonstration processes of a real-time video frame differentiator based on an external memory interface is described in this paper. The video frame differentiation process is successfully implemented on both low cost and high-end FPGA development boards, then demonstrated by using sample videos at 1024x768@60 and 1920x1080@60 resolutions. Input video resolution, video buffer size on memory and burst size of the memory interface can be configured before implementation. Publisher's Version

Derin evrişimsel sinir ağları (ESA) pek çok sınıflandırma probleminde olduğu gibi anlambilimsel görüntü bölütlemede de çok ciddi başarı göstermiştir. Fakat derin ağların eğitilmesi hem zaman alıcıdır hem de geniş bir eğitim veri kümesine ihtiyaç duymaktadır. Bir veri kümesinde eğitilen ağın başka bir görev ya da veri kümesine uygulanabilmesi için transfer öğrenme ile yeniden eğitilmesi gerekmektedir. Transfer öğrenmeye alternatif olarak ağ katmanlarından çıkarılan öznitelik vektörleri doğrudan sınıflandırma amaçlı kullanılabilir. Bu bildiride genel ESA mimarilerinden elde edilen özniteliklerin eğitim gerektirmeyen bir görüntü etiketleme yönteminde kullanılmasının sınıflandırma başarımına katkısı incelenmiştir. Derin ağlarda ‘öğrenilmiş’ öznitelikler ile SIFT gibi ‘el yapımı’ özniteliklerin birlikte kullanılmasının etiketleme doğruluğunu artırdığı gösterilmiştir. Varolan ön eğitimli ağların kullanılması sayesinde önerilen yaklaşım herhangi bir veri kümesinde yeniden eğitime gerek olmadan kolayca uygulanabilmektedir. Önerilen yöntem iki veri kümesinde test edilmiş ve etiketleme doğruluğu benzer yöntemlerle karşılaştırmalı olarak sunulmuştur. Deep convolutional neural networks (CNN) have shown significant success in many classification problems including semantic image segmentation. However training of deep networks is time consuming and requires large training datasets. A network trained in one dataset could be applied to another task or dataset through transfer learning and retraining. As an alternative to transfer learning, feature vectors that are extracted from network layers could be directly used for classification purposes. In this paper we investigate the improvement in classification performance when features extracted from generic CNN architectures are used in an image labeling algorithm that does not require training. We show that the use of 'learned' features from deep networks together with 'hand-crafted' features such as SIFT increases the labeling accuracy. Since existing pre-trained networks are used, the proposed approach could be easily applied to any dataset without any retraining. The proposed method is tested in two datasets and labeling accuracies are compared with similar existing methods. Publisher's Version

Reports on the status of microwave education and technological development in Turkey. Publisher's Version Q2 WOS: 000467132500001