Phillip K. Wong

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.

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.

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.

Modeling intermodulation distortion in SiGe HBTs

The accuracy of large-signal equivalent circuit models of silicon-germanium heterojunction bipolar transistors (HBTs) is examined. Nominal transistor model parameters are found to be insufficiently accurate to reliably predict intermodulation distortion (IMD) in individual heterojunction bipolar transistors. A method for optimizing the model parameters to give a more accurate simulation of IMD performance is outlined. For best results, some form of parameter optimization for IMD should be considered as a part of the parameter extraction procedure. Differences between transistor models are observed and analyzed by comparing measured IMD power levels with computer simulation results. The Gummel-Poon model is found to be simpler and easier to optimize than the Kull-Nagel model.

Comparison of DC, RF, and dispersion properties of SOI and strained-SOI N-MOSFETs

The operating performance of SOI and strained-SOI N-MOSFETs are compared. In particular, these properties are examined in detail: 1) electron mobility and DC characteristics, 2) high frequency behavior, 3) dispersion and self-heating effects, and 4) buried oxide interface trap density. Our results demonstrate that SSOI technology can improve f/sub t/ and f/sub max/ conservatively by up to 50% without excessive dispersion/self-heating. Furthermore, measurements indicate that the SSOI wafer bonding process can produce an acceptable buried oxide interface trap density.

The influence of model parameters on accurate IMD simulations in HBTs

Nominal transistor model parameters are often insufficiently precise to accurately predict intermodulation distortion (IMD) behavior in individual heterojunction bipolar transistors (HBTs). A procedure for optimizing the model parameters to achieve a more accurate simulation of IMD performance is presented. Measured IMD data for silicon-germanium HBTs of differing emitter sizes are compared to IMD simulations to illustrate the optimization process.