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A Reflective Practicum for Transforming Instructor’s Industrial Skills into the Teaching of Electromagnetics
Abstract
Contemporary electromagnetic Computer-Aided Design (CAD) tools augmented with parametric and optimization capabilities are extensively used in industry for design, validation, and prototyping to reduce time-to-market, resources, cost, and risks associated with the development of new systems. Unfortunately, this technology still remains largely underutilized in undergraduate ElectroMagnetics (EM) education. This paper describes an approach for stimulating the analysis and design learning experience of undergraduate systems engineering students by engaging them in cooperative, experiential, simulation-assisted teaching and research activities utilizing project-based pedagogy. A case study is chosen in the realm of microwave-assisted material processing, which is not typically covered in undergraduate engineering curricula. The objective is to increase students’ interest in EM fields and waves by providing a well-rounded learning experience to break the monotony often encountered in the heavily theoretical and abstract topics involved with a minimum of complex analytical formulations, reinforce fundamental principles and mathematical analyses offered in the class, foster students’ motivation and enthusiasm, reflect on today’s technological advancement in industry, and stimulate participation of undergraduate students in open-ended research problems.
Index Terms— Electromagnetic Education, Cavity Resonators, ANSYS HFSS, CST Microwave Studio, Microwave Heating, Simulation-Based Learning
- INTRODUCTION
It is globally acknowledged that engineering EM courses are often regarded by students to be abstract, mathematically saturated, and the most difficult that any undergraduate can take [1]-[7]. In a traditional undergraduate EM course, the fundamentals of Maxwell’s equations and their physical applications are conveyed from the instructor to students via visual representation of spoken and written words explaining the set of physical phenomena observed by Gauss, Ampere, Faraday, and Maxwell’s contribution to Ampere’s law (displacement current density) via vector mathematical manipulations such as curl, divergence, Laplacian, and gradient applied to static and time-varying field quantities. Heavy reliance on mathematical derivations to solve simple and idealized canonical problems often obscures intuitive understanding and requires a long learning cycle to comprehend and connect to real-world applications. For most students this is a passive learning experience which cultivates the belief that finding the right formula, and apply vector operators to phasor quantities using hand-held calculators are the key to solving a problem. This approach creates a substantial gap between classroom teaching and real-world engineering problems. Moreover, this approach is far removed from current professional engineering practice to be a satisfactory experience for students.
Closed-form analytical solutions for problems encountered in radio-frequency components, wireless systems and antennas are only available under idealized assumptions such as highly symmetric, oversimplified, 0-D (point source radiator), 1- or 2-D homogeneous geometries and uniform excitation, to mention a few. Additionally, even those unrealistically simplified problems, such as analyzing the resonant frequencies, internal fields, and power dissipated within closed, Perfectly Electric Conducting (PEC) rectangular and cylindrical cavity resonators symmetrically loaded with dielectric material involve analytical manipulations not trivial for most undergraduate students where the simple use of pencil and paper cannot provide the answer. On the other hand, reliance on rigorous analytical treatment produces more confusion than elucidation creating a void for basic design skills such as how to couple power into the cavity. It should be noted that although hand calculations significantly reinforce understanding of fundamental concepts, contemporary CAD simulation tools are instrumental to introduce design and real-world applications that assist students to infer the usefulness of the theory, reflect on the limits of analytical expressions, investigate the implications of various design alternatives, and ask “what if” questions.
A project-based pedagogical approach has been implemented in a core EM fields and waves course offered in the Systems Engineering Department of the EIT College at UALR. The instruction focuses on exploiting the industry-grade ANSYS’s High Frequency Structure Simulator (HFSS) (http://www.ansys.com) and CST Microwave Studio (MWS) (http://www.cst.com) to solve and design modern engineering problems. These tools are used as supplementary instructional aids (not as a substitute) for the classical style of education to link theory to real-world applications and improve design skills using progressive, multiple case studies with design content. The hypothesis being tested in the teaching pedagogy is how to transform one of the multidisciplinary industrial and academic research experience acquired by the instructor [8]-[14] to a teaching and learning paradigm to be used by students both inside and outside the classroom in order to develop essential skills required in professional engineering practice.
Although many recent careers in industry require competence in HFSS and/or CST; however, there is a notable lack of adequate coverage in many electrical and/or systems engineering curricula worldwide. It should be noted that the need to incorporate simulations to enhance undergraduate EM teaching and their educational benefits has been demonstrated in [2], [3]. Abstract mathematics need no longer be the sole approach of analysis. Students whose strengths might lie instead in numerical and computational analysis, algorithm development, and programming can become productive contributors as well. More importantly, CAD tools enhance the students’ abilities to solve open-ended design problems, work well in teams, and communicate effectively in written and oral forms.
A key objective of the approach reported in this paper is to promote active classroom learning and self teaching by engaging students in design projects that link theory to actual systems. Students are trained, in a mixed laboratory/classroom environment, on the use of state-of-the-art, time-domain and frequency-domain EM solvers to enhance teaching and research using applications that involve analysis of mode tuning and design of realistic cavity resonators under different loading conditions for high-power microwave material processing. Students are given the opportunity to learn and discover material independent of the instructor and take pride in their work and creativity.
HFSS and MWS allow students to study the response of a device in the time domain and display frequency characteristics via a discrete Fourier transformation. Students can test many configurations in order to compare their merits and conduct parametric studies to evaluate the influence of different design parameters on the performance, contribute their elements to the model, and investigate how the optimization of a design parameter may impact the overall performance metrics. Moreover, the projects provide opportunities for students to acquire soft skills, such as teamwork, self regulation, commitment, and communications skills through daily logs, formal technical laboratory reports, and oral presentations at the end of the course.
The teaching methodology is based on project-driven curriculum that offers hands-on laboratory experiences with a progressive range of complexities. Suites of progressively more difficult hands-on simulations, that do not require programming and/or sophisticated analytical skills which are beyond the undergraduate level, have been offered to give students opportunities to learn by “doing.” This approach motivated students to develop their analytical abilities to formulate, model and simulate real-world engineering problems, analyze, validate, and optimize the final solution. The curriculum promotes research-based educational strategies by involving undergraduate students in research activities early in their careers. Students developed sufficient skills and confidence to engage in professional presentations and publications in their senior year [15], [16].
The rest of the paper is organized as follows. In section II, the instructional pedagogy is described. Course details are presented in section III. Representative laboratory tutorials and design projects are provided in section IV and V, respectively. Finally, section VI concludes the paper. The models presented in this paper are available to instructors and students upon request.
II. DESCRIPTION OF THE INSTRUCTIONAL PEDAGOGY
Integrating theoretical inquiries of Maxwell’s equations with experimentation to illustrate real-world applications is more pronounced in undergraduate EM courses. Abstract concepts extracted from experiments such as the set of four equations of Maxwell, vector operations on 3-D spatially and temporally varying field quantities and the diverse topics to be covered tend to frustrate students who have been dealing mostly with scalar quantities. Regrettably, a major obstacle for undergraduate students is prerequisite mathematical skills [17]. Moreover, due to time constraints and the need to cover a wide range of topics of practical nature in the context of systems engineering education, we have developed a new teaching paradigm to impart an intuitive feeling and build knowledge in a hands-on fashion.
Advanced concepts are introduced through a series of progressively more difficult, challenge-based, hands-on simulations to give students opportunities to learn by “doing.” This is achieved through in-class demonstrations, laboratory sessions, and design-oriented assignments performed after the prerequisite topics are taught in class. Additionally, student teams are engaged in application-oriented, open-ended research projects involving design of realistic cavity resonators to meet specific performance requirements. The semester-long projects require students to design, analyze, and optimize prototypes based on detailed design specifications. The projects culminate in a functional model implementation and require validation, presentation, and formal documentation.
An “open laboratory” policy is used. Students can access the software tools via VMware any time so that students can better schedule when to work on their projects and share experiences more effectively and a Teaching Assistant is allocated to assist students when needed. At the end of the semester, students’ collaborative teams present their work in written as well as oral forms providing incentive for the development of effective oral and written communication skills in order to experience the processes they would encounter in the daily practice of industrial settings. These activities are synergistic with the Accreditation Board for Engineering and Technology (ABET) Criteria [17] which emphasizes design experience, exposure to modern engineering design tools and contemporary engineering applications. With these thoughts in mind, the curriculum has accounted for the following specific pedagogical issues:
- Break the passivity of traditional lecture formats by teaching students how to apply knowledge, not just acquire it;
- Create an atmosphere of self discovery and experimentation with realistic constraints;
- Help students to identify limitations of analytical solutions and the benefits drawn from CAD tools when idealized techniques fail;
- Provide seamless integration of education and research, incorporate active research results in the classroom, and involve students in hands-on realistic design situations to break down barriers between EM education and its practice in real world;
- Make learning more enjoyable and challenging; and
- Give students a sense of accomplishment.
The textbook used in the course [19], and two research-oriented books covering microwave cavity resonators with applications [20]-[21], provide well-established theoretical treatments to explain fundamental principles. However, applications in undergraduate EM textbooks are introduced using idealized canonical problems with inadequate coverage of research results, and are incapable of providing insight into the limitations of a design topology. For example, classical, oversimplified mathematical models are typically stressed for analysis of microwave cavity resonators without explaining how to couple microwave energy into the cavity. It should be noted that mathematical analysis cannot be dispensed with entirely. Also, we realize that CAD and simulation tools cannot be a substitute for actual laboratory practice- they complement each other. There are distinct advantages in having a teaching aid that can double as a research tool. The curriculum described in this paper provides an easy bridge between learning and doing and integrates research activities into the teaching of the course. This was possible in an environment in which undergraduate students, graduate teaching assistant, and the instructor speak a common language.
Rather than simply delivering passive lectures, the instructor also acted as a higher level manager to whom the teams report, and could consult for advice on how to proceed. The instructor cultivates skills, focuses efforts, and maintains an active environment of learning, exploration, and discovery.
Computer-based simulations of RF devices are fundamentally different from traditional preplanned experiments, which are intended to verify theory and do little to develop design skills. The two sets of experiments are not mutually exclusive; simulation-based experiments are also used for verification purposes to close the feedback loop of learning. CAD allows students to further explore how the performance of a device is affected if the value of a design parameter is altered either intentionally or due to the unavoidable tolerances in the fabrication process. To summarize, students are required to solve realistic problems such as designing a cavity feed structure made of waveguides or coaxial cables taught in class. Ordinarily, this would be a time-consuming task and/or not possible using conventional analytical techniques known to undergraduates, hence we provide students with the tools and training necessary to make these tasks manageable.
- CLASS DETAILS
The course, SYEN 3356: Electromagnetic Fields and Wavesis the first course which introduces students to EM waves and high-frequency systems and is an obligatory core subject in the curriculum. The course provides students with an understanding of transmission lines, waveguides, cavity resonators, power dissipation, and mismatch compensation. The course is accompanied by a laboratory to capture students’ interest. Course delivery is based on an appropriate combination of lectures, simulation-based demonstrations and tutorials, and traditional hardware-based laboratory experiments. The simulation tutorials and design projects are based on students’ interests, elective courses and careers students are targeting, and to a large extent the projects to be chosen for the two-semester Capstone Design Course.
Concepts in vector calculus, analytic geometry, linear algebra, physics, electric circuits and systems are prerequisites. Basic EM, encompassing electrostatics, magnetostatics, wave propagation and optics, are also taught in two prerequisite physics courses with their associated laboratories prior to taking SYEN 3356. The first week is devoted to reviewing the physical interpretation of gradient, divergence, curl, and ending with Helmholtz theorem for vector fields. The concept of field is defined at first, in terms of its measurable effect; electric and magnetic forces.
In contrast to classical EM courses, only two weeks are allocated to review electrostatics and magnetostatics including dielectrics, continuity equation and steady currents, magnetic forces and media. Then, Ampere’s and Faraday’s laws are introduced culminating in Maxwell’s equations in differential and integral forms and the Poynting’s theorem. Topics discussed next are transmission lines, Smith chart, plane-wave propagation in conducting and dielectric media, coaxial cables, waveguides, and cavity resonators. The scattering matrix is introduced to characterize mismatch and dissipation losses in cascaded, lumped, and distributed circuits.
Classes are presented as three one-hour lectures a week complemented by laboratory work. The laboratory/demonstration sessions are carefully sequenced to remain in step with lecture content and progress in sophistication in synchronization with the students’ increasing familiarity with the topics and CAD tools. Each student is required to complete a project over the semester in topics of current research interest; one case of which is industrial microwave heating as described in this paper. The projects foster inquiry-based learning using industry driven applications to tightly couple the course to the laboratory that brings a multidisciplinary, broad-based approach to analysis, design, and optimization. Projects allow students to go as far as they can at their own pace, provide variable time and flexible schedules that enhance quality and in-depth study, incentives for self-direction, self-motivation, self-activity, and thinking as a part of a team.
- LABORATORY TUTORIALS
Two weeks are used to introduce the theory of cavity resonators [20] and [21] including series and parallel resonant circuits, unloaded and loaded Q factors, transmission line resonators, rectangular and circular cavities, excitation of aperture coupled cavity, cavity perturbation, and critical coupling. Instead of repertory problems found at the end of chapters, students are provided with a fully interactive, step-by-step description of a series of CAD-based tutorials along with an input file for the simulation procedure. A typical scenario is for a student to read the tutorial, execute simulations, analyze and post process the intended results, respond to questions, compare results against well-documented analytical solutions if available, and then submit a report that describes the results obtained.
Students are introduced to the proper set of boundary conditions that must be enforced on the outer boundaries of the computational domain: Perfectly Electric Conducting (PEC), Perfect Magnetic Conducting (PMC), Surface Impedance Boundary Conditions (SIBC), and how to excite a port within the waveguide feed in the case of a driven problem. The reflection coefficient, S_{11} is used to evaluate the efficiency within which microwave energy is coupled into the cavity and absorbed by the load and conducting cavity walls.
Students are instructed on how to conduct convergence tests to ensure that the fields have been sufficiently sampled in space by automatically varying the number of grid points iteratively to select the spatial resolution required for a predefined convergence criterion such that maximum deviation of the parameter of interest does not change significantly between at least two consecutive adaptive grids. For solutions obtained from time-domain solver of CST, time stepping for each mesh is stopped when the maximum energy inside the structure has decayed to less than 80 dB below its maximum value for an accurate characterization of the cavity in the frequency domain. A concise summary of these tutorials is provided in Table I.
Table I Simulations-based tutorials for SYEN 3356
Projects | Description |
Tutorial 1
Rectangular Cavity |
To demonstrate how to evaluate the eigenmodes, eigenvalues, and Q factor of a simple closed, rectangular cavity. The cavity geometry is created as a brick shape defined by three parameters: length, width, and height. The lowest three resonance frequencies are calculated. The students are asked to determine the dimensions such that the cavity resonates at a fundamental frequency of 915 MHz. Next, students used the optimizer of MWS with the goal of maximizing the separation between the fundamental mode and the second-order mode. Students comparedthe numerical results against the analytical solution using the closed-form expressions reported in [20] for the resonant frequencies and associated Q factors assuming PEC boundaries and an electrical conductivity of 5.8×10^{7} S/m. |
Tutorial 2
Cylindrical Cavity |
A closed cylindrical cavity is considered defined by the height and radius. Only three eigenmodes have been considered, where mode 1 and mode 2 are identical except for polarization. The radius and height were chosen such that the resonant frequency of the dominant mode is 915 MHz. The Q factor is calculated for a conductivity of 5.8×10^{7} S/m and compared against the analytical value reported in [20] for modes one to three. |
Tutorial 3
Spherical Cavity |
This tutorial considers a PEC spherical cavity defined by its radius. Only three modes are considered which are identical except for polarization. The simulated values for the resonant frequencies and Q factors of the first three modes are compared against the analytical solutions [21]. |
Tutorial 4
Loaded Rectangular and Cylindrical Cavities |
Students modeled the dominant resonant frequencies and Q factors of dielectric-filled rectangular and cylindrical cavities. This is the first tutorial in which students must read in depth an IEEE paper, to find the dimensions of the cavities and compare their results against the analytical and measured results reported in [22]. |
V. DESIGN PROJECTS
The utilization of microwave energy in commercial cooking, drying, and rubber industries has been common. Recent advances in microwave technology, improved fundamental knowledge of microwave interaction with materials, and the concurrent blending with the disciplines of physics, chemistry, material science, mechanical, and industrial engineering has led to the development of wider applications in ceramics, mining, chemical synthesis, and environmental waste processing [21], [22].
Traditional design of microwave heating applicators is usually an empirical process relying on accumulated experience, analytical solutions to idealized cases, and trial-and-error methods. Reliable and repeatable experimental design procedures are costly and time consuming due to the several interacting physical mechanisms involved. As there is no analytical solution in most cases, the prospects of modeling a realistic microwave heating applicator stem from the need to control the microwave heating process, complement, and reduce the empiricism involved in an otherwise purely experimental approach.
Unlike lecture-only courses, the pedagogy in SYEN 3356 centers on a sequence of projects not possible to cover in traditional lectures and textbook formats. The projects offered in the course are similar to but more complex than the in-class tutorials. Students are required to review technical papers [8]-[15], [22], [24] for state-of-the-art examples. Self study is strongly encouraged because of the limited lecture hours. Each project is allotted four weeks where students spend about four hours per week to be able to complete the project and preparing project reports. Students are divided into two groups; the first group performs simulations using HFSS; while the second group uses CST. Each group consists of two students who work together during each laboratory session. At the end of each project, the two groups interact with each other to explain the details of their simulations. For the next project, the software assignment is reversed; therefore, at the end of the course, students in each team become familiar with both HFSS and MWS. Due to space limitations, only five projects involving transmission-type, single-mode, and multimode resonant structures are briefly described as depicted in Table II.
Table II Simulations-based projects for SYEN 3356
Projects | Description |
Project 1: TE_{10n} microwave heating cavity | The cavity consists of a section of a 3.175-mm thick hollow WR 975 waveguide (24.765 cm 12.3825 cm) terminated by an adjustable short-circuit plunger at one end and a conducting plate containing a circular iris in the center of the transverse wall on the other end. Microwave energy is injected into the cavity via an adjustable coupling iris. Samples are introduced via a 25.4-cm long, cylindrical choke tube of 6.985-cm inner diameter. The tube passes through the center of the broad wall near the region of maximum electric field strength to mitigate leakage of microwave energy. First, students are required to find the position of the tuning plunger such that the cavity is tuned at a resonant frequency of 915 MHz. Every design process involves a number of approximations. For example, in arriving at the initial design, the feed waveguide and cavity are normally assumed to be PEC and the coupling aperture is ignored to make the design process tractable. In real life, however, waveguides have finite conductivities and the coupling mechanism affects the resonant frequency and the quality factor. Next, losses due to the coupling aperture, load, and imperfectly conducting walls are investigated. The radius of the iris is optimized by students in order to achieve maximum power transfer into the load when the source is tuned at the resonant frequency of the cavity. Students are asked to compute the eigenfunctions (electric and magnetic field distributions), eigenvalues (resonant frequencies), unloaded, external, and loaded Q-factors, optimum iris size for critical coupling, and shift in resonant frequency caused by the introduction of the processed material. According to experimental data, the optimum radius should lie between 5 cm to 6 cm. The iris radius is changed from 5 cm to 6 cm with a step size of 0.1 cm. The magnitude of S_{11} is selected as the cost function. The optimization tools of ANSYS and CST are used to infer the optimal iris diameter to achieve maximum electric field strength within the processed material. The students conclude that the minimum reflection occurs between 5.2 cm and 5.4 cm. With this information, the iris variable is reanalyzed from 5.2 cm to 5.4 cm. with a step size of 0.05 cm. Minimum reflection found from optimization tools is at a radius of approximately 5.3 cm. This should produce optimal power transfer into the cavity.
TE_{10n} microwave heating cavity |
Project 2:Testing Electromagnetic Analysis Methods (T.E.A.M.), Workshop Problem 19, Microwave Field in a Loaded Cavity | The cavity is of the TM_{010} type, consisting of an air-filled conducting cylinder containing a centered dielectric rod. A small rectangular aperture to a rectangular waveguide couples the cavity [25].
TM_{010} microwave heating cavity A circular cylindrical cavity, excited in the TM_{010} mode, is considered. The cavity is 90 mm in diameter, and 85 mm in height. The cavity is coupled via an iris to an 85 mm long rectangular waveguide excited in the dominant TE_{10} mode. The traverse cross-sectional dimension of the feed waveguide is 86.36 mm x 43 mm. The iris extends 43 mm along the height of the waveguide and is 15 mm in width. The cavity is concentrically loaded with a 9 mm diameter cylindrical load, 85 mm in height, and of dielectric constant, ε_{r} = 2.6- j0.01. The cavity is resonating around 2.5 GHz. The length of the iris is assigned to students as a design variable. The effect of the length of the iris on the coupling efficiency is examined in terms of 1- S^{*}_{11}S_{11}. The iris length is changed from 14 mm to 16 mm in 10 steps. Students show that the optimum value lies between 14.44 mm to 14.68 mm. Losses due to the imperfectly conducting cavity walls and the feed to the cavity are taken into consideration by employing surface-impedance boundary conditions. Results are presented for the unloaded, external, and loaded Q-factors, optimum iris size for critically coupling, and shift in resonant frequency caused by the introduction of the processed materials. Simulations are compared to the experimental results reported in [25]. |
Project 3 Concentric Irises in a Cylindrical Waveguide | Evaluate the scattering parameters of a transmission-type cavity consisting of two concentric irises in the cylindrical waveguide. A standard WR-75 waveguide with a broad-wall dimension of a = 1.905 cm, height b=a/2,excited in the dominant TE_{10} mode, concentrically couples microwave energy into a cylindrical cavity of radius R=a, and height H = 4.09448 cm. Results obtained from HFSS are compared against those derived from MWS as well as experimental and mode-matching results reported in [27]. Students are asked to find the amplitude and phase of S_{11} and S_{12} from HFSS and MWS over the frequency range from 8 GHz to 15 GHz. The students then perform comparison to reveal the differences between the two methods and demonstrate that they are well within the experimental tolerances and the measured data provided in []. |
Project 4
Multimode Cylindrical Cavity Coupled by a Rectangular Waveguide |
Investigate two single-port multimode resonant-type cavities. The cavities have been designed, constructed, and tested by the author [9], [10], [12], [13]. The feed waveguide is a standard WR-975 with a broad-wall dimension of a = 24.765 cm, height b=a/2,and length c = 20 cm. The waveguide, excited in the dominant TE_{10} mode, couples microwave energy into a cylindrical cavity of diameter D and height H. Microwave power at 915 MHz is fed into the top wall of a stainless steel cavity. The height of the cavity is H = 116.8 cm, diameter, D = 30.5 cm, and the wall thickness is 0.95 cm. The cavity is loaded with a sample of height, h_{L} = 22.9 cm, the dielectric constant of the load, _{r} = 4.2 – j 0.25. An HP8642B synthesized sweep generator and an HP8410C network analyzer were used to identify the resonant frequencies and to measure S_{11}. Students present the amplitude and phase of S_{11} when the cavity is partially loaded with a material of _{r}= 5.3 – j 0.19, and height of 10 cm. Results are shown when the waveguide and cavity walls are modeled as PEC and when SIBC are enforced with electrical conductivity, = 3.7 10^{5} S/m. The agreement between the measured and simulated values of S_{11 } is very good. For the second cavity, microwave power is coupled through the side wall of a stainless steel multimode cavity. The dimensions of the cavity are: D = 30.47 cm, H = 121.87 cm, h_{L} = 20.31cm, the distance from the upper broad wall of the waveguide to the top wall of the cavity, h_{w} = 30.47cm,and ε_{r}= 3.6 – j0.19. Next, students present comparisons against measurements of the frequency response of S_{11} performed when the cavity is loaded at room temperature with 50 lb of a dielectric sample with ε_{r} = 5.3 – j0.19, density of 104 lb/ft^{3}, and height of 19.37cm. |
Project 5
Octagonal Cavity |
Designing, optimizing, and evaluating octagonal-shaped cavity, which can be adapted to different materials of larger volumes without invoking internal and/or external tuning mechanisms [14]. Additionally, the cavity is not sensitive to frequency instabilities of commercial magnetrons due to its relatively smaller Q factor. The students are asked to find the cavity height that produces high, uniform energy density within the material to be processed in the frequency range from 890 MHz to 940 MHz. Two cylindrical cutoff tubes are located at the center of the top and bottom faces. The choke tube is 25.4 cm in height and 6.985 cm in diameter to minimize energy leakage while allowing proper insertion of the processed material. The width of the applicator is chosen to accommodate energy coupling via a WR975 waveguide and the length of the cavity is fixed at 53.34 cm. The cavity is terminated by a short circuit at one end while microwave energy is coupled into the cavity at the other end. The diameter of the load is the same as the choke tube, and its height is initially set to 12.7 cm. In order to determine the height of the cavity that maximizes the energy coupled into the applicator and hence deposited in the load, the height is varied from 20 to 31 cm while observing S_{11}. Since the cavity walls are assumed to be PEC, the objective function is to minimize S_{11}, whichis a proper measure of the power dissipated in the load. The load used is chosen to have _{r}= 3 – j0.3. The advantage of the extra height that the octagonal shape offers, relative to the TE_{10n} cavity, is demonstrated. A load of the same height as the cavity is chosen to test the performance for two different materials. |
VI. CONCLUSION
This paper introduces an educational paradigm in the realm of systems engineering aimed at providing students with traditional EM analysis at the level of undergraduate textbook and focused on building and improving the design skills in the field of single- and multi-mode cavities for microwave-assisted material processing. The goal is to respond to challenges imposed by the rapid evolution of CAD industry to keep pace in providing students with modern education. By using the most currently favored pedagogical model for teaching design, project-based learning, the introduction of applications has been accelerated, students’ motivation to delve into their theoretical formulation has been fostered, students’ productivity increased, and students were able to tackle sophisticated research problems. Students learned how to handle open-ended problem solving skills, project planning, significance of published material, conducting literature survey, benchmarking previous research, and finally published their first article [14], [15]. An innovative, student-centered, and project-based classroom/laboratory platform has been realized that seamlessly integrates theoretical lectures and laboratory experience utilizing industry-standard equipment and testing procedures with modern design automation tools as supplementary instruction and research aid for making EM fields and waves more appealing to students and to modernize the teaching of microwave cavity resonators. The distinguishing feature of the curriculum is the seamless integration of fundamental theoretical principles, laboratory, and sophisticated and yet easy to use state-of-the-art simulation technology not only to reinforce lecture material taught in class, but also as a bridge between academic and industrial practice to foster integration of research and teaching.
The implementation of the curriculum proved to be highly motivational and educational, and makes it possible to introduce meaningful real-world problems into the classroom. During the past five years, students made direct use of the projects and papers were subsequently published by the students [15], [16]. The majority of the students appear more motivated to tackle the difficult theoretical and physical principles involved as they become more aware of their relevance in engineering applications and raised the level of design sophistication taught in the course.
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