Designing Printed Circuit Boards For Microwave Engineering Applications: A Teaching Tool For Engineering Technology Students

This paper will present the results stemming from an undergraduate course in Microwave Engineering Technology at the University of Massachusetts, Lowell. An opportunity to experience the complete process of designing a microwave circuit with printed circuit board (PCB) technology was made possible by a grant provided by the Electrical and Computer Engineering Technology Department Heads Association (ECETDHA). The financial support has allowed the students to apply the theory that is part of the class syllabus to a practical design challenge designed to mimic real–world applications such as wireless phones or GPS devices. Each student was challenged to meet similar, yet unique design specifications. A collaborative environment was fostered. Each student submitted a technical report along with a short presentation to the class as part of their final evaluation. Students were also asked to respond to an on–line questionnaire aimed at evaluating their experience. Responses were tabulated to measure students’ feedback in 3 major areas: their understanding of microwave theory of distributed components; their understanding of the PCB technology applied to microwave design; and their challenges related to the execution of their project. This paper is organized as follows: the main features of the course are outlined first to provide a context within which this project was developed. An outline of the educational approach taken by the author will follow. Then, a description of the projects and challenges faced by the students will be sketched out. A review of the students’ feedback on their experience will be described and discussed. Some suggestions on how to improve this experience will be made before concluding the paper. The Microwave Engineering Technology Course at the University of Massachusetts, Lowell The University of Massachusetts, Lowell, is located in an area where high technology companies are often competing in securing new graduates. At the same time, a need for continuing education of their workforce has often brought back to the University their professionals interested in advancing their technical education. Within this local context, microwave engineering is of particular importance and a course on microwave engineering has been established by the author in spring 2008. The course is entitled Foundations of Microwave Design (course # 17.403) and it is an elective course that the students may take either as part of their undergraduate program; or as individual class. Engineering Technology courses last 14 weeks and consist of a single 3 hour long class per week; all activities, such as a laboratory section, must fit within the allotted weekly time. The prerequisite to Foundations of Microwave Design is Circuits II and Laboratory (course # 17.214) which deals with circuits under sinusoidal excitation. However, the University does not require P ge 15369.2 students to have successfully completed a prerequisite course in order to attend a class. For this reason, the student population may possibly be of any level: for instance, at the time of this project, the class was attended by both freshman and senior students. Its syllabus has originally been conceived to cover two major aspects of microwave engineering: 1. linear distributed components; and 2. basic circuits for wireless communication Item 1 is considered a core constituent of the course1 and addresses a major pedagogical objective – the introduction of typical microwave engineering concepts such as wave propagation, wavelength and discontinuities in the signal path to name a few. The analysis of transmission lines is the subject elected to introduce the students to these fundamental ideas. To facilitate the students’ understanding, great emphasis is made on the application of transmission lines: Smith chart, scattering parameters, matching circuits, substrates are some of the keystones2 of this course. Item 2 is introduced to the students in the context of typical microwave systems such as General Positioning Systems (GPS) and wireless phones. Because of the ubiquity of cell phones, it is easy to focus the students’ attention to the concepts of down and up-conversions, electrical noise, radio-frequency power and the basic metrics used to characterize a radio transmission3: power gain, noise figure, 1dB compression point, etc. This balanced approach between theory and applications has received good feedback from past students as it meets both the curiosity of the young students and the needs of the professionals. In January 2009, the Electrical and Computer Engineering Technology Department Heads Association (ECETDHA) funded a proposal by the author to allow the students of the spring 2009 Foundations of Microwave Design class, to design, layout, manufacture and characterize a printed circuit board for microwave applications. This project has been executed by the students with tools that are industry standards – Agilent’s Advanced Design System (ADS) software for design, simulation, layout; and a vector network analyzer (VNA) for testing. Only manufacturing has been outsourced to a commercial vendor located in Canada, in line with common practices of this industrial sector. The pedagogical approach The opportunity provided by ECETDHA demanded a review of the current syllabus in order to maximize the students’ understanding of the class topics through the execution of a real–world project within the standard 14 weeks. The experiential learning approach4 is considered with great favor by the author as a guideline5 a) for teachers to facilitate the student’s understanding of a subject; and b) for students to learn through experience how to handle unforseen challenges that cannot be taught through textbooks.The author’s teaching experience aligns with scholarly research that a broad range of P ge 15369.3 ways of taking and processing information exists among individuals6. In order to meet the students’ diverse – and certainly unknown at the start of the class – approach to learning, the syllabus was modified to accommodate the PCB project in terms of both content and schedule. Indeed, the project requirement of focusing on the design, layout and characterization of a microwave circuit imposes reconsidering the syllabus structure and content in order to answer the question What topics should be taught to the students for them to fully appreciate the PCB project? Further, a successful execution of the project can be achieved only if the sequence of the subjects to be taught is also reviewed – the question to address is: When should a particular topic be scheduled for presentation in relation to the other subjects and to the project? The author’s answers to the what and when questions have been based on a pedagogical approach that attempts to balance theory with practice; and aims at demonstrating to the students that theoretical models are key to guide the design of practical applications to a successful outcome. A strong theoretical component becomes an integral part of the student’s practical experience as it helps the students evaluate the outcome of a decision against the expected result. These considerations provide an indication on which subjects ought to be taught in order to support the execution of the PCB project (the answer to the what question); and to sort the subjects correctly (the answer to the when question). Therefore, the lectures have been reshaped to time the following topics within the allotted 14 weeks: