Investigating The Relation Between Optimum Guard Interval And Channel Delay Spread For A Mc-Cdma System,
2012
TÜBİTAK
Investigating The Relation Between Optimum Guard Interval And Channel Delay Spread For A Mc-Cdma System, Çeti̇n Kurnaz, Hülya Gökalp
Turkish Journal of Electrical Engineering and Computer Sciences
This paper demonstrates a novel approach to determining the optimum guard interval for a multicarrier code division multiple access (MC-CDMA) system. Analytical expressions for useful and interference power are derived as a basis for comparison. From these, an expression for the signal-to-noise ratio of a detected bit is derived and used to determine the optimum guard interval for a given channel profile and system parameters. In contrast to other works, we use channel models based on actual measurements and we highlight important differences from theoretical models to support our approach. From our results, we propose an empirical rule for optimum …
Reconfigurable Antenna Structure For Rfid System Applications Using Varactor-Loading Technique,
2012
TÜBİTAK
Reconfigurable Antenna Structure For Rfid System Applications Using Varactor-Loading Technique, Yusuf Sevi̇nç, Adnan Kaya
Turkish Journal of Electrical Engineering and Computer Sciences
A novel method is presented for electrically tuning the frequency of a compact radio-frequency identification (RFID) tag antenna. A tuning circuit, comprising a radio frequency (RF) switch and discrete passive components, was completely integrated into the antenna element, which is thus free of DC wires. The low-profile printed antennas were fabricated together with the layouts of the DC control circuits and other RF/baseband circuit footprints. A surface-mounted varactor was applied as a frequency-tuning element at the proper places of the meandered slots in the compact antenna. Prototype designs showed that the in-band frequency (return loss < 10 dB) was tunable from 2.4 GHz to 2.8 GHz when the bias voltage varied from 4 V to 7 V. The impact of the tuning circuit on the antenna's return loss and radiation pattern were experimentally studied through comparison with the performance of a reference antenna not incorporating the tuning circuit. The proposed frequency tuning concept can be extended to more complex compact structures as well as other types of antennas to give enhanced electrical performance.
Improved Square Properties Of Idea,
2012
TÜBİTAK
Improved Square Properties Of Idea, Mete Akgün, Hüseyi̇n Demi̇rci̇, Mahmut Şami̇l Sağiroğlu, Pinar Kavak
Turkish Journal of Electrical Engineering and Computer Sciences
Block cipher encryption algorithms generally process on word structures of fixed length such as 8 or 16-bits. IDEA is one of the most widely used block ciphers and operates on 16-bit words. Square analysis is a method that exploits the word structure of block ciphers. Some square distinguishers of IDEA are given in previous studies. The best attacks against IDEA use square-like techniques. In this paper, we focus on the square properties of the IDEA block cipher. We consider all fixed word combinations of the plaintext to investigate the structural behavior of the algorithm. We observe that the cipher can …
Application Of Asymmetrical Periodic Signals As Test Vectors For Analog Fault Detection: A Novel Perspective Of Classical Concepts, Badar Ud Din Ahmed, Wang Youren, Najam-Ud-Din Ahmed
Turkish Journal of Electrical Engineering and Computer Sciences
Analog fault diagnosis is a field of paramount importance, and test signal generation is an important prerequisite for analog fault detection. Several stimuli have been used as input test vectors. This study presents a novel approach for the adoption of classical methods and signals for fault detection. This involves the use of asymmetrical periodic signals and comparison of their effectivity in maximizing output response between faulty and conforming circuits. The technique helps to determine a minimal set of test signals for a circuit. It also enables the test designer to identify the parts of the frequency spectra of various signal …
Automatic Tracking System For Weather Satellite Image Reception,
2012
TÜBİTAK
Automatic Tracking System For Weather Satellite Image Reception, Wassila Leila Rahal, Noureddine Benabadji, Ahmed Hafid Belbachir
Turkish Journal of Electrical Engineering and Computer Sciences
We present a tracking ground system for low Earth-orbiting (LEO) satellite image reception composed of a software part and a material part. The developed prediction software (LAAR-TRACK) ensures an efficient satellite orbit determination. It is based on the simplified general perturbations model (SGP4) used by the North American Aerospace Defense Command for generating orbital elements. LAAR-TRACK gives the azimuth and the elevation needed for the antenna to signal, in real time, LEO satellites during their passage above the ground receiving station. The software is loaded on a computer directly connected, via the parallel port, to the tracking interface that we …
Voltage- And Current-Controlled High Cmrr Instrumentation Amplifier Using Cmos Current Conveyors,
2012
TÜBİTAK
Voltage- And Current-Controlled High Cmrr Instrumentation Amplifier Using Cmos Current Conveyors, Hamdi̇ Ercan, Sezai̇ Alper Teki̇n, Mustafa Alçi
Turkish Journal of Electrical Engineering and Computer Sciences
A new approach to the design of an instrumentation amplifier using only 2 CMOS current-controlled conveyors and an active resistor is introduced. The new approach, which has no passive components, offers a wide bandwidth and a high common-mode rejection ratio (CMRR). Electronically controllable gain by voltage and current is also obtained by this new circuit. The circuit is simulated using the parameters of a 0.35-\mu m TSMC CMOS technology. Theoretical analysis of the circuits was carried out, and the performance of the block circuit was confirmed through PSpice simulation results.
Trellis-Based Optimization Of Layer Extraction For Rate Adaptation In Real-Time Scalable Stereo Video Coding,
2012
TÜBİTAK
Trellis-Based Optimization Of Layer Extraction For Rate Adaptation In Real-Time Scalable Stereo Video Coding, Nükhet Özbek
Turkish Journal of Electrical Engineering and Computer Sciences
The concept of quality layers (QLs) has been adopted in the scalable video coding standard to enable optimal rate adaptation of precoded video in the rate-distortion sense. QLs were previously extended to stereo and multiple-view scalable video for efficient transport of 3DTV over the Internet. However, it is not possible to use the QL method in applications that require real-time encoding since the priority determination process assumes the availability of the whole video sequence. In this work, a trellis-based online rate adaptation is proposed for real-time scalable stereo video coding, with a delay of 1 group of pictures (GoP). The …
Low-Complexity Channel Estimation For Ofdm Systems In High-Mobility Fading Channels,
2012
TÜBİTAK
Low-Complexity Channel Estimation For Ofdm Systems In High-Mobility Fading Channels, Mahmut Yalçin, Aydin Akan, Hakan Doğan
Turkish Journal of Electrical Engineering and Computer Sciences
Nowadays, multicarrier transmission is very popular because of the high data rate requirement of wireless systems. Orthogonal frequency-division multiplexing (OFDM) is a special case of multicarrier transmission. It is considered an effective technique for frequency-selective channels because of its spectral efficiency, its robustness in different multipath propagation environments, and its ability of combating intersymbol interference. Losing subchannel orthogonality causes interchannel interference, but many conventional channel estimators assume that the channel is time-invariant during one OFDM symbol. This assumption causes error floors along the OFDM symbol for high-mobility cases. In this paper, we propose 2-dimensional pilot symbol-assisted channel estimation for wireless …
Fast Software Multiplication In F_2[X] For Embedded Processors,
2012
TÜBİTAK
Fast Software Multiplication In F_2[X] For Embedded Processors, Serdar Süer Erdem
Turkish Journal of Electrical Engineering and Computer Sciences
We present a novel method for fast multiplication of polynomials over F_2 which can be implemented efficiently in embedded software. Fast polynomial multiplication methods are needed for the efficient implementation of some cryptographic and coding applications. The proposed method follows a strategy to reduce the memory accesses for input data and intermediate values during computation. This strategy speeds up the binary polynomial multiplication significantly on typical embedded processors with limited memory bandwidth. These multiplications are usually performed by the comb method or the Karatsuba-based methods in embedded software. The proposed method has speed and memory advantages over these methods on …
Optimization And Coordination Of Svc-Based Supplementary Controllers And Psss To Improve Power System Stability Using A Genetic Algorithm, Ali Darvish Falehi, Mehrdad Rostami, Aref Doroudi, Abdolaziz Ashrafian
Turkish Journal of Electrical Engineering and Computer Sciences
In this piaper, a lead-lag structure is proposed as a main damping controller for a static VAR compensator (SVC) to diminish power system oscillations. To confirm the transient performance of the proposed controller, it was compared to a proportional integral derivative (PID) damping controller. Power system stability improvement was thoroughly examined using these supplementary damping controllers as well as a power system stabilizer i(PSS). The generic algorithm (GA) is well liked in the academic environment due to its immediate perceptiveness, ease of performance, and ability to impressively solve highly nonlinear objectives. Thus, the GA optimization technique was applied to solve …
Study And Control Of 5-Level Pwm Rectifier-5-Level Npc Active Power Filter Cascade Using Feedback Control And Redundant Vectors, Thameur Abdelkrim, El Madjid Berkouk, Karima Benamrane, Tarak Benslimane
Turkish Journal of Electrical Engineering and Computer Sciences
The purpose of this paper is to develop a control and regulation method for the input DC voltages of a 5-level neutral point clamping (NPC) active power filter (APF). This APF is applied for the enhancement of medium-voltage network power quality by compensation of harmonic currents produced by an induction motor speed variator. In the first part, the authors present a topology of a 5-level NPC voltage source inverter and its simplified space vector pulse width modulation (SVPWM) control strategy. In the second part, the control strategy of the 5-level pulse width modulation current rectifier is presented. In the third …
Cascade Fuzzy Logic Control Of A Single-Link Flexible-Joint Manipulator,
2012
TÜBİTAK
Cascade Fuzzy Logic Control Of A Single-Link Flexible-Joint Manipulator, İsmai̇l Hakki Akyüz, Zafer Bi̇ngül, Selçuk Ki̇zi̇r
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents the design and control of a single-link flexible-joint robot manipulator. A cascade fuzzy logic controller (FLC) was used to remove link vibrations and to obtain fast trajectory tracking performance. The cascade FLC structure includes 3 different FLCs. The input variables of the first and the second FLCs are the motor rotation angle error, its derivative, and the end-point deflection error its derivative, respectively. The outputs of these controllers are the inputs of the third FLC, which yields the control signal to the flexible robot arm. All of the FLCs were embedded in a DS1103 real-time control board. …
Circuit Model And Parasitic Parameter Extraction Of The Spark Plug In The Ignition System,
2012
TÜBİTAK
Circuit Model And Parasitic Parameter Extraction Of The Spark Plug In The Ignition System, Quandi Wang, Yali Zheng, Jihui Yu, Jin Jia
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents a circuit model of the spark plug in the ignition system for conducted electromagnetic interference (EMI). Based on the spark plug's current discharge channel, the circuit model of the spark plug is established with the parasitic parameters and the air-gap model. The parasitic parameters of the spark plug are extracted with the finite element method, and the air-gap model of the spark plug is analyzed using the electric circuit principles and the air-discharge theory. The simulation and measurement results validate this model. Furthermore, this model confirms that the spark plug discharge is the main conducted EMI source …
Stability Of The Adaptive Fading Extended Kalman Filter With The Matrix Forgetting Factor,
2012
TÜBİTAK
Stability Of The Adaptive Fading Extended Kalman Filter With The Matrix Forgetting Factor, Cenker Bi̇çer, Esi̇n Köksal Babacan, Levent Özbek
Turkish Journal of Electrical Engineering and Computer Sciences
The extended Kalman filter is extensively used in nonlinear state estimation problems. As long as the system characteristics are correctly known, the extended Kalman filter gives the best performance. However, when the system information is partially known or incorrect, the extended Kalman filter may diverge or give biased estimates. An extensive number of works has been published to improve the performance of the extended Kalman filter. Many researchers have proposed the introduction of a forgetting factor, both into the Kalman filter and the extended Kalman filter, to improve the performance. However, there are 2 fundamental problems with this approach: the …
Short-Term Nodal Congestion Price Forecasting In A Large-Scale Power Market Using Ann With Genetic Optimization Training,
2012
TÜBİTAK
Short-Term Nodal Congestion Price Forecasting In A Large-Scale Power Market Using Ann With Genetic Optimization Training, Majid Moazzami, Rahmat Allah Hooshmand
Turkish Journal of Electrical Engineering and Computer Sciences
In a daily power market, price and load forecasting are the most important signals for the market participants. In this paper, an accurate feed-forward neural network model with a genetic optimization Levenberg-Marquardt back propagation training algorithm is employed for short-term nodal congestion price forecasting in different zones of a large-scale power market. The use of genetic algorithms for neural network training optimization has a remarkable effect on the accuracy of price forecasting in a large-scale power market. The necessary data for neural network training are obtained by solving optimal power flow equations that take into account all effective constraints at …
Packet Traffic Features Of Ipv6 And Ipv4 Protocol Traffic,
2012
TÜBİTAK
Packet Traffic Features Of Ipv6 And Ipv4 Protocol Traffic, Cebrai̇l Çi̇fli̇kli̇, Ali̇ Gezer, Abdullah Tuncay Özşahi̇n
Turkish Journal of Electrical Engineering and Computer Sciences
Nowadays, the IPv6 protocol is in a transition phase in operational networks. The ratio of its traffic volume is increasing day by day. The many provided facilities for IPv6 connection increasethe total IPv6 traffic load. IPv6-over-IPv4 tunnels, pilot programsto provide IPv6 connections, IPv6/IPv4 dual stack operating systems,and free IPv6 tunnel brokers cause the IPv6 protocol to expand quickly. For efficient resource utilization, the characteristics of network traffic should be determined accurately. Many traffic characterization studies regarding IPv4 have demonstrated that most of the network traffic is self-similar. Self-similarity causes significant impacts on network performance. With the increasing volume of IPv6 …
Neutral Current Wave Shape Analysis Using Wavelet For Diagnosis Of Winding Insulation Of A Transformer,
2012
TÜBİTAK
Neutral Current Wave Shape Analysis Using Wavelet For Diagnosis Of Winding Insulation Of A Transformer, Patthi Sridhar, Birendra Prasad Singh, Pulapa Venkata Kanaka Rao
Turkish Journal of Electrical Engineering and Computer Sciences
Insulation failure within the windings of a power transformer arises due to over voltages, under voltages, notches, glitches, etc. A widely used technique to detect these power transformer insulation failures during an impulse test is the comparison of neutral current waveforms. Any shift in the recorded waveforms between reduced and full voltage confirms the existence of a fault in the windings. Hence, a proper analysis of neutral current waveforms is necessary to assess the condition of the insulation of power transformer winding. In order to carry out a wave shape analysis, a 61 MVA, 11.5/230 kV generator transformer is used …
Finite Element Modeling Of A Superconducting Fault Current Limiter,
2012
TÜBİTAK
Finite Element Modeling Of A Superconducting Fault Current Limiter, Lale Ergene, J. Keith Nelson, Raghunath Parthasarathi
Turkish Journal of Electrical Engineering and Computer Sciences
This paper summarizes the work done to show finite element modeling results on a high temperature superconductor fault current limiter (FCL). The paper also gives the small mock-up design of the matrix FCL and its finite element model (FEM). It also discusses the limitations of the FEM and explains how the results from the FEM compare with the experimental data derived for the configuration. A 3-dimensional FEM has been used because of the structure of the real geometry, which does not show any plane or axisymmetric features.
Characterization Of A Total Power Radiometer,
2012
TÜBİTAK
Characterization Of A Total Power Radiometer, Murat Celep, Şenel Yaran, Yakup Gülmez, Ari̇f Dolma
Turkish Journal of Electrical Engineering and Computer Sciences
The performance parameters of a total power radiometer designed as a noise measurement system for the frequency range of 12-18 GHz were investigated. The total power radiometer included a low-noise radio frequency section, a narrow-band intermediate frequency section, an average power detector, and a symmetric microwave switch. The radiometer's stability versus time was 0.343 \times 10^{-5} mW/h and its stability against temperature fluctuation was 0.0035 mW/K. The temperature fluctuation of the radiometer was less than 4 mK. We proved that there was no need for active temperature control to obtain stable radiometer gain.
Improvement Of Smart Card Based Password Authentication Scheme For Multiserver Environments,
2012
TÜBİTAK
Improvement Of Smart Card Based Password Authentication Scheme For Multiserver Environments, Zuowen Tan
Turkish Journal of Electrical Engineering and Computer Sciences
In multiserver (MS) environments, it is preferable for a remote user to login to different service provider servers by keying in the same password. Recently, Wang et al. proposed an improvement on the dynamic identity-based smart card authentication scheme of Liao and Wang for MS environments. Sandeep et al. improved the dynamic identity-based smart card authentication scheme of Hsiang et al. for MS architecture. However, we found that the schemes of Wang et al. and Sandeep et al. failed to provide service provider server authentication, perfect forward security, and login scalability. In addition, the scheme of Sandeep et al. was …
