Thomas F. Schubert

Exploring Three-Phase Systems and Synchronous Motors: A Low-Voltage and Low-Cost Experiment at the Sophomore Level

In order to meet changing curricular and societal needs, a three-phase system and synchronous motor laboratory experience for sophomore-level students in a wide variety of engineering majors was designed, implemented, and assessed. The experiment is unusual in its early placement in the curriculum, and in that it focuses primarily on basic understanding of balanced three-phase systems and synchronous motor operating principles. While a low-voltage three-phase system and subfractional-horsepower electric motors were used, experimental results proved to be reliable, accurate, and repeatable. Changes in student knowledge and confidence in the application of that knowledge was assessed and shown to have increased significantly in each case.

Simulation of the effects of companding on quantization noise in digital communication systems

An original simulation program to explore the effects of /spl mu/-law companding in digital communication systems is presented. The program allows the user to explore companding for arbitrary input signals. Reconstructed analog signals and quantization noise for both companded and uncompanded systems are graphically displayed. Quantization signal-to-noise ratio is calculated and compares favorably with theory. The program was written using the mathematical simulation package MathCAD. >

A quantitative comparison of three Bode straight-line phase approximations for second-order, underdamped systems

Bode straight-line approximations are an extremely useful tool in the study of system frequency response. These approximations give good insight into the frequency variation of the amplitude and the phase of a system response without the use of computer simulation or complex calculations. Three Bode straight-line approximations to the phase of second-order, underdamped systems are subjected to quantitative error analysis. The magnitude of the maximum phase error and root-mean-square phase error are computed for each phase approximation as a function of the system damping coefficient. The results of the analysis indicates superiority of the little-known decade-fraction phase approximation technique.

A low-cost design experience for junior-level electronics circuits laboratories through emulation of industry-printed circuit board design practice

Over a 2-year period, printed circuit board layout design and test were included in the laboratory portion of the second of two junior-level electronic circuits courses. Printed circuit board design using industry-accepted board specifications and standard industry Gerber file export experience was developed. The students’ printed circuit board design experience emulated real-world situations and cost criteria. The instructor served as the fabricator in this model of the industrial design situation. Students individually used industry standard schematic capture and layout software to develop a printed circuit board for a simplified discrete µA741 operational amplifier. The layout designs were submitted as industry standard Gerber files electronically to the instructor/fabricator for evaluation. Grades were assigned by evaluating the accuracy and cost effectiveness of the design by minimizing traces, reducing printed circuit board geometry, and limiting the number of vias, which ultimately reduces fabricator tooling cost. Feedback was provided by the instructor who acted as the industry fabricator to individual students. A single fabricated printed circuit board, designed by the instructor (and fabricated by a commercial printed circuit board manufacturer), was delivered to students for assembly and test. By delivering a single printed circuit board design to students, fabrication costs can be minimized and students can inspect the delivered board as an exemplar. Assessments of the student perceptions of knowledge of and confidence in applying printed circuit board techniques in designing and releasing a printed circuit board were conducted prior to and after the printed circuit board layout design and test. On a 5-point scale, overall student-reported knowledge increased by 2.14 and overall student confidence increased by 1.20 points. Faculty assessment of knowledge, as measured by scoring short answers to knowledge statements, correlated well with student report and showed an average increase of 2.70.

Melding engineering into a liberal arts tradition: a unique nine-semester BS/BA electrical engineering program

In 1986, the University of San Diego (USD) began an initiative to enhance the science portion of its liberal arts tradition. A new nine-semester program in Electrical Engineering was created as one of the flagship components of that initiative. Founding and building an engineering program, not only within a liberal arts university but also within a College of Arts and Sciences, presented a challenging set of objectives and constraints to the founding Electrical Engineering faculty. In particular, satisfying the extensive general education component at USD while fulfilling the needs of a quality engineering program presented an interesting set of tradeoffs. The resultant program is the only EAC/ABET accredited nine-semester course of study automatically leading to a dual Bachelor of Science and Bachelor of Arts degree in Electrical Engineering. The dual nature of the degree proclaims the breadth of academic experiences required of every student. This paper chronicles the first ten years of Electrical Engineering at USD: the growth from its first classes in 1987 to national recognition.

The use of a simple computer math package to demonstrate complex communication systems principles

In the study of communication systems, it is often difficult for students to develop a true understanding of the more complex systems and signal principles without exercising an appropriate communication system. While actual hardware usage is arguably the best technique for student investigation, the complexity of and costs associated with appropriate commercial or instructional communication hardware systems make such systems, in many cases, unattractive in a university setting. Often a more appropriate solution to augmenting student learning is computer simulation. A series of original computer exercises that demonstrate several communication principles has been developed by the author to be used as student laboratory exercises or as a supplement to hardware laboratory exercises. The paper describes the simulation exercises, gives complete listings of the programs, and reports on the use of these exercises in a university setting to augment a course in communication system principles. Among the communication systems topics investigated in the exercises are quantization noise, distortion, companding, and Nyquists criteria for zero intersymbol interference. While the exercises were written using the mathematical computation package MathCAD, adaptation to other similar packages is not difficult.

Fundamentals of Electronics: Book 3 Active Filters and Amplifier Frequency Response

This book, Active Filters and Amplifier Frequency Response, is the third of four books of a larger work, Fundamentals of Electronics. It is comprised of three chapters that describe the frequency dependent response of electronic circuits. This book begins with an extensive tutorial on creating and using Bode Diagrams that leads to the modeling and design of active filters using operational amplifiers. The second chapter starts by focusing on bypass and coupling capacitors and, after introducing high-frequency modeling of bipolar and field-effect transistors, extensively develops the high- and low-frequency response of a variety of common electronic amplifiers. The final chapter expands the frequency-dependent discussion to feedback amplifiers, the possibility of instabilities, and remedies for good amplifier design. Fundamentals of Electronics has been designed primarily for use in an upper division course in electronics for electrical engineering students and for working professionals. Typically such a course spans a full academic year consisting of two semesters or three quarters. As such, Active Filters and Amplifier Frequency Response, and the first two books in the series, Electronic Devices and Circuit Applications, and Amplifiers: Analysis and Design, form an appropriate body of material for such a course.

Fundamentals of Electronics:Book 1 Electronic Devices and Circuit Applications

This book, Electronic Devices and Circuit Application, is the first of four books of a larger work, Fundamentals of Electronics. It is comprised of four chapters describing the basic operation of each of the four fundamental building blocks of modern electronics: operational amplifiers, semiconductor diodes, bipolar junction transistors, and field effect transistors. Attention is focused on the reader obtaining a clear understanding of each of the devices when it is operated in equilibrium. Ideas fundamental to the study of electronic circuits are also developed in the book at a basic level to lessen the possibility of misunderstandings at a higher level. The difference between linear and non-linear operation is explored through the use of a variety of circuit examples including amplifiers constructed with operational amplifiers as the fundamental component and elementary digital logic gates constructed with various transistor types. Fundamentals of Electronics has been designed prima ily for use in an upper division course in electronics for electrical engineering students. Typically such a course spans a full academic years consisting of two semesters or three quarters. As such, Electronic Devices and Circuit Applications, and the following two books, Amplifiers: Analysis and Design and Active Filters and Amplifier Frequency Response, form an appropriate body of material for such a course. Secondary applications include the use in a one-semester electronics course for engineers or as a reference for practicing engineers.

A laboratory exercise to improve student understanding of dominant pole analysis and high-frequency modeling of Field Effect Transistors

In the quest for increased student understanding of the principles underlying high-frequency response of Field Effect Transistor amplifiers, a laboratory exercise employing a unique method to determine the intrinsic transistor model capacitances was used. The method employs two simple measurements: determination of the high 3-dB frequency for a common-source amplifier being driven by a Thévenin source with two different output resistance values. Circuit simulation results utilizing these experimentally determined intrinsic capacitances show much greater correlation to experimental results than those typically obtained using manufacturer-supplied values. Students participating in the laboratory exercise reported good gains in knowledge levels and reasonable gains in confidence levels.

A comparison of experimental results to those in "evaluation of bipolar junction transistor transconductance in practical applications"

An attempt to recreate the experimental results given in the paper by C.D. Ferris (see ibid., vol.36, p.293-5, 1993) was made using a modern transistor curve tracer. The experimental results were not reproduced. The new experimental results seem to validate the common usage of /spl eta//spl ap/1 in describing bipolar junction transistors.