Osman L. El-Sayed

MODFET 2-D hydrodynamic energy modeling: optimization of subquarter-micron-gate structures

Using a two-dimensional hydrodynamic energy model incorporating nonstationary electron dynamics and nonisothermal electron transport (which characterizes submicron-gate MODFETs), the main physical phenomena that govern the device performance at 300 K are highlighted. This covers velocity overshoot effects, stationary-domain formation, and real space transfer. The model is then used systematically to predict the precise values of the small-signal parameters for different bias conditions. The potential performance improvement achieved by reducing the gate length below 0.2 mu m is investigated. It is shown that improvement in transconductance is achieved through gate-length reduction if a severe restriction on the aspect ratio is respected. >

Two-dimensional simulation of submicrometer GaAs MESFETs: surface effects and optimization of recessed gate structures

The surface potential effect in GaAs MESFETs causes a depleted zone to form not only between the source and gate, but also between the gate and drain. The consequences of this phenomenon on the device behavior, the DC and AC characteristics, and the expected performance are studied. For this purpose, a two-dimensional resolution of the basic semiconductor equations is used. This model takes into account relaxation effects by including an energy relaxation equation. The dependence of MESFET characteristics such as transconductance, output conductance, and capacitance on the dimensions of the zone where surface potential effects occur is given. Some interesting conclusions concerning the optimization of recessed-gate structures are drawn. >

REALIZATION OF COMPOSITE RIGHT/LEFT-HANDED TRANSMISSION LINE USING COUPLED LINES

This paper presents a method to construct composite right/left-handed transmission line using coupled lines. A general procedure to design a composite right/left-handed unit cell is presented. The procedure was used on a specific coupled line configuration, which is the coupled microstrip lines with slotted ground. It is shown that by proper design of the slotted ground, the coupling between the two microstrip lines can be increased dramatically keeping practical dimensions for the coupled line width and spacing. Moreover, with accurate slotted ground design, equal even and odd electrical lengths can be achieved. The performance of this composite right/left-handed line, which is characterized by backward waves with phase advance, is demonstrated by both simulated and measured results and they show good agreement. The realized composite right/left-handed transmission line has a broad bandwidth and small size.

Performance analysis of sub-micron gate GaAs MESFETs

Abstract A novel 2-D numerical model incorporating nonstationary electron dynamics is used to investigate the complex transport phenomena governing the operation of sub-micron gate GaAs MESFETs. A detailed theoretical analysis of different phenomena observed in subhalf micron devices is given. These include velocity overshoot, stationary and travelling domain formation, soft pinch off, excess drain current etc. The small signal parameters g m , g d and C gs and their dependence on bias condition are evaluated. The effects of physical quantities such as mobility and interface barrier on carrier injection and transport and consequently on device performance are presented.

Impedance Characterization of a Two-Post Mounting Structure for Varactor-Tuned Gunn Oscillators

A lumped equivalent circuit is used to characterize a two-post waveguide mounting structure frequently utilized in varactor-tuned Gunn oscillators. Analytical expressions for the different elements are derived. Comparison with experimental results enabled us to refine the model by the introduction of correction factors which compensate for the simplifying assumptions of the theoretical model. This equivalent circuit would facilitate the optimization of the performance of this type of oscillator.

2-D simulation of degenerate hot electron transport in MODFETs including DX center trapping

A comprehensive 2-D hydrodynamic energy model which is capable of describing nonstationary electron dynamics and nonisothermal transport within submicrometer MODFETs (TEGFETs or HEMTs) is presented. The model accounts for carrier degeneracy, deep DX center levels, and conduction outside the quantum well, thereby including bulk and parasitic MESFET effects. A technique for handling carrier degeneracy is presented. The authors also present two techniques developed to overcome the complexity of solving the coupling between the model nonlinear partial differential equations (PDEs). These cover DX center trapping kinetics and the energy derivatives in the Jacobian, particularly regarding the energy-conservation equation. The model is so informative that it highlights the main physical phenomena which govern device behavior such as velocity overshoots, stationary domain formation, buffer injection, back injection, and local longitudinal field inversion at the gate entrance of the channel. The model is systematically used to predict the DC and small-signal performance of submicrometer gate AlGaAs-GaAs MODFETs operating at room temperature. >

Leaky Wave Antenna Realization by Composite Right/Left-Handed Transmission Line

This paper presents a realization of composite right/left handed transmission lines using coupled microstrip lines. This structure exploits the advantages of the microstrip lines, while increases the coupling by a ∞oating conductor at the ground plane. The performance of this composite right/left-handed line is demonstrated by both simulated and measured results, and they show good agreement. The designed line has broad bandwidth with low losses and small size. A novel dominant mode leaky wave antenna design, using the previous structure, is presented with backward to forward scanning capability.

Generalized Analysis of Parallel Two-Post Mounting Structures in Waveguide

An analytical expression is obtained for the reactance of parallel two-post mounting structures having unsymmetrical strip and gap positions and different strip and gap widths. An equivalent circuit is derived and analytical expressions for its components established giving a physical insight into the problem of coupling between the two gaps. The analysis is based on deriving a variational expression for the structure reactance from the boundary conditions at the structure position. The theoretical results are experimentally verified for a wide range of coupling conditions. Exploitation of this model for the design of wide-band varactor-tuned negative resistance oscillators and multidiode parallel mounts in general is discussed.

Realization of composite right/left-handed transmission line using broadside coupled coplanar waveguides

Broadside coupled coplanar waveguides are used to realize a composite right/left-handed transmission line, which is characterized by antiparallel group and phase velocities. The transmission line design depends on the electromagnetic coupling between coupled lines. The broadside coupled coplanar waveguides was chosen to achieve tight coupling with practical dimensions, which reflects an enhancement in the bandwidth. Experimental verification for the design is demonstrated with good agreement to the simulated values. The proposed composite right/left-handed transmission line has a broad bandwidth.

Engineering and engineering education in egypt

Engineering education in Egypt is a mirror of the countrys history, a result of the confluence of foreign influences (French, British, Swiss, German, Soviet, American) and national desires for sovereignty, development, and Pan-Arabism. American political and economic influence in the most recent period can be seen in the current dominance of the Anglo-Saxon model in engineering education, particularly in such disciplines as electronics, telecommunications, computer engineering, petroleum engineering, biomedical engineering, and aeronautical engineering