مجله مهندسی برق و الکترونیک ایران
سال دوازدهم شماره 2 (پاییز 1394)

In this paper، analytical models for NBTI induced degradation in a P-channel triple gate MOSFET and HCI induced degradation in an N-channel bulk FinFET are presented، through solving the Reaction-Diffusion equations multi-dimensionally considering geometry dependence of this framework of equations. The new models are compared to measurement data and gives excellent results. The results interpret accurately thegeometry dependence of the time exponent of NBTI and HCI degradations in these device structures. Inaddition، the floating-body effect on NBTI phenomenon in an undoped double-gate (DG) MOSFETs is modeled and investigated by solving the one-dimensional (1-D) Poisson''s equation considering NBTI effect، in inversion region for different stress voltages and different device body thicknesses. The accuracy of the model is verified by the finite difference method (FDM). These results show that in FB devices، accumulation of NBTI generated electrons in the device body brings about reduction of the body potential and the oxide field. Therefore the interface trap generation rate in FB devices decreases which leads to smaller amount of interface traps and degradation in these devices compared to BT devices.

In this paper، design، analysis and fabrication of a low loss capacitive RF MEMS shunt switch، which made on the coplanar waveguide transmission line and alumina substrate in the frequency band of 40-60 GHz، is presented. The CPW is designed to have 50Ω impedance matching on the alumina substrate. Then the desired switch is designed with appropriate dimensions. Afterward the important parameters are obtained by finite element and full-wave electromagnetic simulations by CoventorWare and HFSS. It is shown that for the designed switch، pull-in voltage is 19. 25v، insertion-loss is 0. 8dB، return-loss is more than 9. 8dB and the isolation is 50dB. At the end، the laboratory sample of designed switch is fabricated on alumina substrate and tested، and the possible parameters are obtained. We concluded that the designed switch has appropriate insertion and return loss and good isolation، and fabricated switch has acceptable properties.

We propose a novel two state and all-optical controllable switch using DIT، Kerr effect and interaction between quantum dots (QD) and quantum electrodynamics cavity (CQED). The two state and all optical controllable switch is coupled to photonic waveguide from a rapid nonlinear environment (photonic crystal) and CQED. We consider the nano-crystal are doped to crystal photonic cavity as a 4-level atomic system then design the proposed all-optical switch with quantumatic methods. We wright Hamiltonian of the system and realize the dynamic equation then we show the optical switching operation by calculating the transition probability for two waveguides with simulations in MATLAB. In this paper by choosing the proper values for basic parameters an improved all-optical switch were obtained for example the switching speed is increased 3 times with first control field، 7 times with second control field rather than previous designs.

In this paper, LiMn2O4 spinel cathode materials have been successfully synthesized by solid-state reaction. Surface of these particles modified by nanocoating of LiFePO4. Synthesized products were characterized by Xray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDX). The results of electrochemical tests showed that charge/discharge capacities and charge retention of battery were significantly enhanced. This improved electrochemical performance is due to LiFePO4 phosphate layer on particles surfaces of LiMn2O4 cathode materials.

Lock and settling times are two parameters which are of high importance in design of DLL-based frequency multipliers. A new architecture for DLL-based frequency multipliers in digital domain is designed in this paper. In the proposed architecture instead of using charge pump, phase frequency detector and loop filter a digital signal processor is used. Gradient algorithm is used in the proposed circuit to improve the DLLs parameter. The architecture can be easily implemented by simple digital signal processor (even with analog circuits). Also, simulations are provided in a case of 11 delay cells and input frequency of 300MHz. The simulation results show that the output frequency is 11 times of reference frequency (3.3 GHz) and lock.

Suppressing clutter is one of the most crucial phases in radar signal processing. Also, Blind Source Separation (BSS) is one of the recent and very important problems in signal processing that shows its efficiency in many applications. Degenerate Unmixin Estimation Technique (DUET) is one of the Underdetermined BSS algorithms that separate sources from mixtures using only two mixtures. In this paper, we use this algorithm in order to suppressing clutter and detecting target. Synthetic target and clutter are generated to perform simulated experiment. Then, we suppress the clutter from the radar signal mixture using the proposed method based on DUET BSS. Finally, the efficiency of the method is shown by comparison with the delay line canceller. This comparison shows that the method is able to suppress clutter and detect target.

In this paper, Electromagnetic capability (EMC) has substantial role in projects with electromagnetic properties. In this paper, EMC in transponder payload for communication satellite is evaluated. EMC problems are assessed in two levels, system and subsystem level. Charging, grounding and bonding are studied about system level. In general, subsystem tests involve radiated emission, conducted emission, radiated susceptibility and conducted susceptibility. EMC test requirements for space application and shielding matter as effective method for EMC are presented.

An effective design procedure is devised for the optimum design of a versatile and useful six-port planar microstrip power divider. An equivalent circuit is developed for the divider; which is composed of line sections and asymmetrical T-junctions. The method of least squares is applied to the equivalent circuit of the divider for its optimum design. This power divider is capable of providing various power division ratios for different combinations of the output ports (for example 3 or 2 outputs) for the same fixed design configuration. The power divider may then be fine-tuned by the full-wave software to obtain an optimum design for the divider. The method of least squares may also be used to design power dividers with arbitrary power division ratios at their output ports.

Directional couplers are passive devices which are used as power dividers and combiners in microwave, millimeter and terahertz systems. By the use of substrate integrated waveguides (SIW) for the design of such devices, the advantages of waveguide and printed circuit (PC) technologies are utilized simultaneously, such as low cost, small size, low transmission and radiation losses. In this paper, the method of least squares is employed for the design and optimization of symmetrical and asymmetrical multi-section branch-line-couplers incorporating impedance matching at its input and output ports. The equivalent circuit of the branch-line coupler is obtained and its transmission and scattering matrices are derived, which are eventually used for the construction of an error function. Its minimization leads to the determination of the dimensions of the coupler and its optimum design. The design specifications of coupler include its power division ratios, port impedances and frequency bandwidth. Three prototype models of branch-line-couplers are designed, namely a 6dB singlesection coupler, a symmetrical 3dB two-section coupler and an asymmetrical 3dB two-section coupler. The latter coupler is fabricated and measured. The designs of couplers are verified by the HFSS full-wave computer software with very good agreement.

In e-commerce and e-banking environments, one of the most risks or challenges which must be considered, is the risk of online fraud specially phishing attacks. In this study, we use some visual and technical identifies of a phishing web site as parameters to implement an expert system to diagnose this type of attack in electronic banking. In the proposed system, we use 27 different features as the expert system parameter in assessing a web page, which has been classified into six parts. The artificial neural network is used to determine the weight of some of these parameters. By combination of values which could be extracted for each of these parameters, we design the system knowledge base. The inference engine of the expert system shell has used to determine the result of each part of input parameters. Finally, the results of each part compared with others to evaluate and output the result as the final inference system is provided. Based on studies conducted on several real samples of phishing web sites, the results showed that the proposed system has relatively good result to detect such attacks.

Because of rapidly rising network traffic, ISP providers are trying to create new network structures and extend more resources to control the growth of demands. It is important to efficiently split the network bandwidth among different sources so that each user has enough bandwidth. Traffic engineering is used to achieve this goal. Performing reliable and efficient network operations as well as improving the utilization of network resources, are the aims of traffic engineering. These objectives are reached by exploiting appropriate routing techniques and the result is the increase of network ability to create different services without congestion. Sending the traffic of each stream to multiple paths and applying the load balancing algorithms cause higher network throughput and lower end-to-end delay compared to traditional single path routing algorithms. This paper presents a brief introduction of multipath routing algorithms and introduces load balancing algorithms categorized into two groups of state dependent and state independent algorithms.

Atrial Fibrillation is a supra ventricular tachyarrhythmia, which is characterized by the deterioration of atrial mechanical function and aberrant. It has become a social and economic problem because a large percentage of the world population suffering from this disease. The early diagnosis of this fatal cardiac Arrhythmia can be prevented and managed it. In this study, we used non-invasive methods based on nonlinear analysis of ECG signal, to identify individuals prone to Atrial Fibrillation. This study consists of three steps, the first step is preprocessing of ECG signals collected from the Physionet to removed 50 Hz and Artifacts noises, then the HRV signal is extracted from them. Secondly, extract nonlinear parameters from HRV signal, including the Poincare Plot Deviations, Correlation Dimension, Lyapunov Exponent, Approximate Entropy and Sample Entropy, and the five characteristics of Recurrence Plot Quantitative Analysis. Third we use a Support Vector Machine classifier for the classification healthy people and those at risk for Atrial Fibrillation Attack. Final results show that Support Vector Machine classifier is able to differentiate healthy from patient population with 93% accuracy, when HRV signal analysis 5 minutes before the onset of Atrial Fibrillation episodes.