Journal of Electrical Engineering

Empirical Equation of Tight Binding Model Parameter to Calculate Bandgap of Semiconducting Single Wall Carbon Nanotube

Golam Rasel Ahmed Jamal — 2012-11-18

Both Mod 1 and Mod 2 type Semiconducting single wall carbon nanotubes over a wide diameter range are studied separately to find their band gap trend. For accurate calculation of their band gaps, modification of nearest-neighbor hopping parameter of the tight-binding model is proposed by considering it as a function of nanotube chiral index and mod value. A simple empirical equation for the nearest-neighbor hopping parameter is presented to produce band gaps of these nanotubes that agree well with simulated data. Empirical data are also compared with experimental data and found to be in excellent agreement with it after adding a flat correction.

Journal of Electrical Engineering
The Institution of Engineers, Bangladesh
Vol. EE 37, No. II, December, 2011

Analysis of a Finite Quantum Well

Imran Khan — 2012-11-18

In this paper one dimensional (1D) quantum confinement in a Finite Quantum Well (FQW) is analyzed through a simulator using MATLAB. A particle behavior inside a FQW is discussed and analyzed. The effect of various parameters such as well boundary thickness, depth of the well and width of the well are discussed. The results are compared with the Infinite Quantum Well (IQW). Different types of potential structures behavior can be analyzed by using this simulator which is very useful before fabrication.

Journal of Electrical Engineering
The Institution of Engineers, Bangladesh
Vol. EE 37, No. II, December, 2011

Analysis of Microwave and Optical Devices by Using Quasi-TEM Finite Element Technique

Ismat Zareen — 2012-11-18

The quasi-TEM finite element analysis of microwave and optical devices has been carried out in this work. The static approach that involves the solution of Laplaces equation can be utilized to characterize many important properties of microstrip lines, microshield lines, and microwave photonic components. In this work, we have incorporated such an analysis to obtain propagation loss in MMIC transmission lines and high-speed electrooptic modulators on LiNbO₃ and GaAs. It is shown that microwave losses play an important role on optical bandwidth of these modulators and the estimation of bandwidth depends on accurate calculation of loss. Here, the Perlows generalized equation has been used to estimate the propagation loss of MMIC lines and very good agreement with the previously published results has been obtained. Very important microwave properties for the design and optimization of MMIC lines and modulators, such as, microwave effective index, characteristic impedance are also calculated by using the capacitance per unit length. These properties have been used in the estimation loss. The dependence of microwave properties with the structural parameters are also investigated and it has been found that considering a dielectric material lossless always lead to an over estimation of optical bandwidth of modulators.

Journal of Electrical Engineering
The Institution of Engineers, Bangladesh
Vol. EE 37, No. II, December, 2011

Minority Carrier Profile and Storage Time of a Schottky Barrier Diode for All levels of injection

M Shahidul Hassan — 2012-11-18

The minority carrier injection and minority carrier stored charge of an n-Si Schottky barrier diode (SBD) considering carrier recombination and blocking properties of the low-high (n-n+) are analyzed. Based on the assumption of slow variation of electric field within the quasi-neutral Si, solution of minority carrier profile is obtained. For the first time, a closed form expression for minority carrier profile p(x) for uniformly doped n-Si SBD is obtained, which is applicable for all levels of injection. Present analysis shows that minority carrier current, charge storage time and current injection ratio depend not only on the length of the n region but also on doping density, recombination within n-Si and effective surface recombination velocity at the low-high (n-n+) interface. Results obtained from the present model are also compared with experimental data available in the literature and are found to be in good agreement.

Journal of Electrical Engineering
The Institution of Engineers, Bangladesh
Vol. EE 37, No. II, December, 2011

Input Current Shaping and Efficiency Improvement of A Three Phase Rectifier by Buck-Boost Regulator

Md. Nazmul Hasan — 2012-11-18

Three phase rectifiers are commonly used in high power applications for their low cost and ease of operation. Rectifiers have non-linear characteristics and draw non sinusoidal input current from ac sources. This causes a number of problems in the power distribution networks. Increase in reactive power, low input power factor, input voltage distortion etc. are some of those problems. In this respect, switch mode regulated rectifiers offer efficient, compact and high efficiency operation. The improvement of input current is possible by addition of Buck, Boost, Buck-Boost or ?uk regulator with single or three phase rectifiers. Pulse width modulation (PWM) technique is used to control the switching devices of these regulators. In this paper, a three phase full wave diode rectifier is analyzed with Buck-Boost regulator. The work shows, when a variable carrier frequency is applied for different duty cycle, the THD of the input current is low and the overall efficiency is more than 80% for lowest and highest output voltages. It provides the facility of control of output voltage to lower and greater than the input voltage efficiently by variation of duty cycle. Previously Buck regulated rectifiers were reported with good power factor and input current THD for constant voltage output. The work of this research will allow variable voltage.

Journal of Electrical Engineering
The Institution of Engineers, Bangladesh
Vol. EE 37, No. II, December, 2011

An Experimental Approach of DLC Film Deposition on Metal Substrates

Muhammad Athar Uddin — 2012-11-18

In this paper an experimental approach of depositing diamond like carbon (DLC) on metal substrates has been described. By electrolysis of 10% (by mass) camphoric solution in methanol, attempts were made to deposit DLC films on Copper (Cu) and Aluminum (Al) substrates at room temperature. Solution is prepared using camphor (C10H16O), a natural source in methanol solvent. At first we applied this approach on Cu substrate and then on Al substrate. The surface morphologies of deposited films were examined by scanning electron microscopy (SEM). A comparison between Cu and Al substrates has been also presented under this approach.

Journal of Electrical Engineering
The Institution of Engineers, Bangladesh
Vol. EE 37, No. II, December, 2011