Elektrik - Elektronik Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12469/47

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Now showing 1 - 13 of 13

Citation - WoS: 14
Citation - Scopus: 16
Bayesian Compressive Sensing for Primary User Detection
(Inst Engineering Technology-IET, 2016) Başaran, Mehmet; Erküçük, Serhat; Cirpan, Hakan Ali
In compressive sensing (CS)-based spectrum sensing literature most studies consider accurate reconstruction of the primary user signal rather than detection of the signal. Furthermore possible absence of the signal is not taken into account while evaluating the spectrum sensing performance. In this study Bayesian CS is studied in detail for primary user detection. In addition to assessing the signal reconstruction performance and comparing it with the conventional basis pursuit approach and the corresponding lower bounds signal detection performance is also considered both analytically and through simulation studies. In the absence of a primary user signal the trade-off between probabilities of detection and false alarm is studied as it is equally important to determine the performance of a CS approach when there is no active primary user. To reduce the computation time and yet achieve a similar detection performance finally the effect of number of iterations is studied for various systems parameters including signal-to-noise-ratio compression ratio mean value of accumulated energy and threshold values. The presented framework in this study is important in the overall implementation of CS-based approaches for primary user detection in practical realisations such as LTE downlink OFDMA as it considers both signal reconstruction and detection.
Citation - WoS: 4
Citation - Scopus: 5
Broadband Equalizer Design With Commensurate Transmission Lines Via Reflectance Modeling
(IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, 2008) Şengül, Metin Y.; Yarman, Sıddık Binboğa
In this paper an alternative approach is presented to design equalizers (or matching networks) with commensurate (or equal length) transmission lines. The new method automatically yields the matching network topology with characteristic impedances of the commensurate lines. In the implementation process of the new technique first the driving point impedance data of the matching network is generated by tracing a pre-selected transducer power gain shape without optimization. Then it is modelled its it realizable bounded-real input reflection coefficient in Richard domain which ill turn yields the desired equalizer topology with line characteristic impedances. This process results in an excellent initial design for the commercially available computer aided design (CAD) packages to generate final circuit layout for fabrication. An example is given to illustrate the utilization of the new method. It is expected that the proposed design technique is employed as it front-end to commercially available computer aided design (CAD) packages which generate the actual equalizer circuit layout with physical dimensions for mass production.
Citation - WoS: 2
Citation - Scopus: 3
Broadband Matching Via Unequal Length Cascaded Transmission Lines
(World Scientific Publ Co Pte Ltd, 2017) Şengül, Metin Y.
In this paper a new approach based on the real frequency technique (RFT) has been proposed to solve broadband matching problems using cascaded unequal length transmission lines. At the end of the design process optimum characteristic impedance and delay values of transmission lines are obtained. Two examples are given to illustrate the utilization of the proposed approach.
Broadband Microwave Amplifier Design With Lumped Elements
(Walter De Gruyter Gmbh, 2016) Şengül, Metin Y.
This study introduces a broadband microwave amplifier design that utilizes the measured scattering parameters of active devices without assuming an initial topology for the matching networks or an analytic form of the system transfer function. The algorithm can be extended to design multistage broadband microwave amplifiers. An example is given to illustrate the application of the proposed method. It was found that the proposed method provides very good initials for CAD tools to further improve amplifier performance by working on the element values.
Design of Phase Shifters With Ladder Stubs Via Real Frequency Technique
(World Scientific, 2020) Şengül, Metin Y.
Generally at high frequencies, lumped-elements are not preferred because of their limited range of values. Therefore, in this work, a kind of phase shifter formed with ladder stubs is studied and a new approach to design phase shifter's low pass and high pass sections which are composed of series or shunt connected open-ended or short-ended stubs is proposed. In the approach, since the main focus is to form low pass and high pass two-port sections, switching process is not considered. First, the designer selects the section type and the total number of stubs in the sections; it is not necessary to fix the two-port section topologies and not necessary to derive the characteristic impedance and delay expressions for the stubs. In the example, 5-stub two-port sections of a 180∘ phase shifter are designed by means of the proposed approach.
Citation - WoS: 3
Citation - Scopus: 3
Explicit Synthesis Formulae for Cascaded Lossless Commensurate Lines
(Fachverlag Schiele Schon, 2008) Şengül, Metin Y.
In literature synthesis of cascaded lossless commensurate lines have been realized via some iterative methods. So to be able to obtain the value of an element which is not the first one the designer has to obtain all the values of the elements connected before the desired one. But in this paper explicit synthesis formulae of the networks containing cascaded lossless commensurate lines up to three have been derived analytically and all the element values can be calculated independently.
Citation - WoS: 10
Citation - Scopus: 9
Mathematical Characterization of Thermo-Reversible Phase Transitions of Agarose Gels
(Taylor & Francis Inc, 2018) Öğrenci, Arif Selçuk; Pekcan, Önder; Kara, Selim; Bilge, Ayşe Hümeyra
The thermal phase transition temperatures of high (HMP) and low melting point (LMP) agarose gels were investigated by using UV-vis spectroscopy techniques. Transmitted light intensities from the gel samples with different agarose concentrations were monitored during the heating (gel-sol) and cooling (sol-gel) processes. It was observed that the transition temperatures T-m defined as the location of the maximum of the first derivative of the sigmoidal transition paths obtained from the UV-vis technique slightly increased by increasing the agarose concentration in both the HMP and LMP samples. Here we express the phase transitions of the agar-water system as a representative of reversible physical gels in terms of a modified Susceptible-Infected-Susceptible epidemic model whose solutions are the well-known 5-point sigmoidal curves. The gel point is hard to determine experimentally and various computational techniques are used for its characterization. Based on previous work we locate the gel point T-0 of sol-gel and gel-sol transitions in terms of the horizontal shift in the sigmoidal transition curve. For the gel-sol transition (heating) T-0 is greater than T-m i.e. later in time and the difference between T-0 and T-m is reduced as the agarose content increases. For the sol-gel transition (cooling) T-0 is again greater than T-m but it is earlier in time for all agarose contents and moves forward in time and gets closer to T-m as the agarose content increases.
Citation - Scopus: 1
Mixed Element Networks With Series Capacitors Separated by Unit Elements
(World Scientific, 2020) Şengül, Metin Y.; Çakmak, Gökhan
In this work, high-pass mixed-element networks with series capacitors separated by unit elements are analyzed. First, the description of the networks via two frequency variables is given. Then, explicit coefficient relations for the descriptive polynomials are derived in terms of the single-variable boundary polynomial coefficients. Finally, the derived relations are used to design a high-pass mixed-element matching network. The series capacitors can be converted to short-ended stubs by means of Richard's transformation. Thus, the obtained network is suitable for microstrip production.
Citation - WoS: 2
Citation - Scopus: 3
Modified Q-Based Real Frequency Design of Narrowband Impedance Equalizer With Complex Terminations
(World Scientıfic Publ Co Pte Ltd, 2019) Şengül, Metin Y.; Yeşilyurt, Gökmen
In this paper, real frequency design equations of narrowband impedance matching network with complex terminations are derived; which are used to design L, Pi and T type of networks. In the approach, there is no need to have termination models with component values, it is enough to have measurement values of termination impedances. A few examples are solved to exhibit the have measurement values of termination impedances. A few examples are solved to exhibit the merits and application of the derived equations.
Citation - WoS: 4
Citation - Scopus: 4
Reflectance-Based Foster Impedance Data Modeling
(Fachverlag Schiele Schon, 2007) Şengül, Metin Y.
A reflectance-based method is presented to model a set of given Foster impedance data as a lossless singly terminated two-port consisting of lumped-elements in short or open termination. The basis of the new method rests on the interpolation of the given data as a realizable bounded-real (BR) reflection function. The desired circuit model is obtained by synthesizing this function. An algorithm to generate the circuit model is presented and an example is included which illustrates the utilization of the proposed modeling method.
Reflection Modeling Based Broadband Matching Network Design
(Walter De Gruyter, 2017) Şengül, Metin Y.
In this paper a new broadband matching network design approach based on reflection modeling is proposed which has two parts: impedance data generation and modeling. In the approach firstly the output impedance data of the matching network is obtained to get the desired flat transducer power gain in the passband. Next the output reflection data are calculated using the obtained impedance data then they are modeled as a bounded real function. Then this function is synthesized and the desired lossless matching network with initial element values is obtained. A double matching example is solved to illustrate the use of the proposed approach. It is seen that proposed approach provides suitable initials for CAD tools for final trimming.
Citation - WoS: 7
Citation - Scopus: 7
Simple Outage Probability Bound for Two-Way Relay Networks With Joint Antenna and Relay Selection Over Nakagami-M Fading Channels
(Inst Engineering Technology-IET, 2015) Erdoğan, Eylem; Güçlüoğlu, Tansal
The performance of a multiple-input multiple-output amplify-and-forward two-way relay network with joint antenna and relay selection is analysed over Nakagami-m fading channels. Both approximate and asymptotic system outage probability expressions are derived and diversity and coding gains for an arbitrary number of antennas relays and fading severity are presented. Finally the analytical findings are verified by numerical examples.
Citation - WoS: 13
Citation - Scopus: 2
Throughput Maximization in Discrete Rate Based Full Duplex Wireless Powered Communication Networks
(John Wıley & Sons Ltd, 2020) Iqbal, Muhammad Shahid; Şadi, Yalçın; Coleri, Sinem
In this study, we consider a discrete rate full-duplex wireless powered communication network. We characterize a novel optimization framework for sum throughput maximization to determine the rate adaptation and transmission schedule subject to energy causality and user transmit power. We first formulate the problem as a mixed integer nonlinear programming problem, which is hard to solve for a global optimum in polynomial-time. Then, we investigate the characteristics of the solution and propose a polynomial time heuristic algorithm for rate adaptation and scheduling problem. Through numerical analysis, we illustrate that the proposed scheduling algorithm outperforms the conventional schemes such as equal time allocation half-duplex and on-off transmission schemes for different initial battery levels, hybrid access point transmit power and network densities.

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