Branimir Pejcinovic

A numerical study of performance potential of Si/sub 1-x/Ge/sub x/ pseudomorphic heterojunction bipolar transistors

A two-dimensional drift-diffusion (DD) simulation and a one-dimensional hydrodynamic (HD) simulation are used to analyze the high-frequency performance of advanced Si BJTs and Si/sub 1-x/Ge/sub x/ pseudomorphic HBTs (PHBTs). The results on similar experimental devices are compared, and good agreement is observed for the Si device. Based on this agreement, it is estimated that equivalent Si/sub 1-x/Ge/sub x/ PHBTs should obtain an f/sub T/ of approximately=70 GHz. DD results give a maximum f/sub T/ of 60 GHz, but HD results suggest the higher figure of 70 GHz. Details of device operation are examined and sources of improved performance identified. Improved HD model parameters, most importantly the mobility, are discussed. >

Comparison of non-linear MESFET models over 1-12 GHz frequency range

This paper is an extension of work done previously on the comparison of non-linear MESFET models. The list of models that are compared includes the Curtice quadratic, Curtice cubic, Statz, Materka, and Advanced Materka models to which the Angelovs model has been added. Furthermore, measurements and model prediction of intermodulation distortion (IMD) are now extended to 12 GHz. The comparison is based on the relative error observed between the measured and simulated DC I-V data, and average error for the model prediction of high frequency gain and IMD. Performance of various models is discussed.This paper is an extension of work done previously on the comparison of non-linear MESFET models. The list of models that are compared includes the Curtice quadratic, Curtice cubic, Statz, Materka, and Advanced Materka models to which the Angelovs model has been added. Furthermore, measurements and model prediction of intermodulation distortion (IMD) are now extended to 12 GHz. The comparison is based on the relative error observed between the measured and simulated DC I-V data, and average error for the model prediction of high frequency gain and IMD. Performance of various models is discussed.

Two-dimensional tensor temperature extension of the hydrodynamic model and its applications

The fundamental assumption that is made in most hydrodynamic simulation programs is the scalar nature of the temperature. In this paper we examine this assumption and present a model that takes into account the full tensorial nature of the temperature. The results show good agreement with 1-D Monte Carlo calculations for a ballistic diode and reproduce some of the qualitative features of 2-D Monte Carlo results for MOSFETs. In terms of terminal currents, 2-D tensor temperature simulation of BJTs shows only small differences when compared with results from scalar temperature formulation. For MOSFETs the differences are up to 15%. Internal distribution of temperature in MOSFETs shows some interesting properties that cannot be reproduced by the scalar temperature hydrodynamic model. The details of the physical models and transport coefficients used are also described.

Just because we teach it does not mean they use it: Case of programming skills

We are assessing the effect of our new freshman electrical engineering course sequence on follow-on courses. One of our assessments is a survey distributed to sophomores in electrical circuits and juniors in microelectronics courses. Roughly one half of freshman year is spent on programming in MATLAB and C, and problem solving using these programming tools. Our observation is that students consider programming important and have reasonably good confidence (self-efficacy) that they can solve problems using MATLAB and C. However, when asked about frequency of use for these tools students report using them somewhere between once a week and once a month. There is a significant number of students who report almost no usage at all. Results are consistent across sophomore and junior years with a slight up-tick in frequency of use for juniors. We are hypothesizing that students do not view MATLAB and C as tools for problem solving but as yet another item to acquire in their studies. Our plan is to change instruction in sophomore courses so that more problem-solving which requires programming will be introduced. The existing survey will be used to measure future improvement.

Evaluation of the operation of depletion-mode SiC power JFET in DC-DC converter applications

This paper presents the system for the evaluation of operation of a depletion-mode silicon carbide (SiC) power junction field-effect transistor (JFET). The main part of the system is a dc-dc step-down converter which represents realistic operating conditions for the switching devices in a synchronous buck configuration. In order to test the importance of the dead-time value on the operation and efficiency of the synchronous buck converter, a precise two-channel time-delay pulse signal generator is developed and its operation is described. The ability to precisely regulate control signal parameters of the high-side FET and low-side FET (switching voltage and current, operating frequency, duty cycle, dead-times, etc.) is needed in order to fully characterise SiC power switches. The functionality of the complete system is verified by measurements performed under various operating conditions.

Artificial neural network in modelling of voltage controlled oscillators with jitter

The use of artificial neural networks in modeling of oscillators with jitter is proposed in this paper. A new method of simulating oscillators with jitter is developed in which an artificial neural network is used to control the signal generator (i.e. oscillator with adjustable parameters: frequency, amplitude, and jitter). A simple and effective way to generate oscillator output with jitter is proposed. This method ensures a simple, robust, fast and accurate modelling of the oscillators with jitter. The method also yields reasonable results for situations not specified in the learning data set because of the generalization property of artificial neural networks and it is suitable for modelling based on measurements. The models of the GaAs voltage controlled differential ring oscillators for circuit simulation software are developed using the proposed method.

Drift-diffusion simulation of InSb devices

A methodology for InSb devices in standard drift-diffusion simulators is presented. Material complexities, such as non-parabolicity, degeneracy, mobility and Auger recombination/generation are explained, and physics based models are developed. This methodology is then applied to the examination of low leakage room temperature InSb photodiodes.

Assessment of student preparedness for freshman engineering courses through assessment of math background

We present an initial investigation of the relationship between math preparedness and student status, and success in freshman electrical and computer engineering courses. We utilize prior math coursework GPA and ALEKS scores as measures of preparedness and find that, with some caveats, they work reasonably well as predictors of success. The majority of our students take freshman engineering courses after completing Calculus 1 or higher. This runs counter to our efforts to engage students in engineering courses first. Students who graduated from high school with some college credit and transfer students with 45-89 transfer credits are susceptible to low grades and high withdrawal rates.

Multimode characterization of parallel plate waveguide

Characterization of parallel plate waveguide multimode propagation is investigated for use in sensing and material parameter extraction applications. Broadband and narrowband measurements are presented and compared to finite difference time domain simulations and analytic solutions which use a Fourier transform mode-matching technique. Agreement is observed between simulation and measurement of field patterns, but analytic solutions require estimates of individual mode contributions. Higher order modes contribute both a greater conductive attenuation and higher coupling loss seen in the larger side lobes of the field pattern.

Applying Scrum project management in ECE curriculum

Scrum is a cyclical project management technique whereby members of a development team work together to define product development strategies in pursuit of a common objective in an adaptable and incremental manner. We have found that Scrum is a promising approach for exposing students to project management of undergraduate engineering projects. But, the technique is not used often in undergraduate education, and it is virtually unknown outside of software engineering circles. We are experimenting with using Scrum in projects across several years of undergraduate engineering education. Our goal is to gradually expose students to project management in order to make their project experiences and learning more efficient and effective. We report on successful initial implementations in freshman courses and senior capstone design courses. Obstacles include expanding practice across all four years, accommodating a diverse student population, and overcoming a lack of experience in assessing Scrum project management.