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Innovative Teaching Methods Help Undergraduates Master Complex RF and Microwave Concepts

Parent Category: 2016 HFE

By Dr. Francesco Fornetti

Introduction

RF and microwave design encompasses if not the most complex, some of the most complex concepts in electrical engineering. Universities are often hampered in their efforts to teach these concepts while undergraduate engineers are eager to learn but lack experience with both design software and lab equipment. 

As a teaching fellow at the University of Bristol in Bristol, United Kingdom, I have developed an innovative RF and microwave teaching method that has proven extremely successful in helping undergraduate students master complex concepts and prepare them for careers in the electronic engineering field.

My post was created as part of a commitment by Bristol University to modernize and enhance the content and delivery of its electronic engineering courses and to introduce innovative and creative approaches to teaching and learning. I was hired because of my extensive experience with the creation of novel, multimedia teaching material, my broad technical background, both in academia and industry, and my enthusiasm.

Teaching Vision

My vision for academic teaching is that it should not be seen as a simple transfer of knowledge and notions between the instructor and the student, but rather as the process of stimulating curiosity and creating enthusiasm about a subject in a way that encourages, inspires, and enables students to explore the subject beyond the classroom walls. 

I also believe that the wide availability of powerful simulation tools, new technology, and broadband Internet access enables academic teaching to be set free from the static setting of a classroom and the black and white pages of a textbook.

Background

My advantage is that I still remember how I felt as a student and what I thought was missing from my courses back in those days. First and foremost, students in my day weren’t taught any specific simulation tool. We were advised to try out SPICE simulators but we were not given any formal training. We could also use a mathematical package if we programmed in the right equations, but it wasn’t straightforward either. This meant that students who weren’t quite as passionate and dedicated as I was simply wouldn’t touch these simulation tools.

This was a major shortcoming. My fellow engineering students and I had many units every year and I believe it would have really helped with our understanding if we had had an easy way of playing around with circuits. For instance, if we added or removed an element we would have to rewrite the equations and see how things changed and this was too time-consuming to be done on so many possible configurations. Also, approaching problems from a mathematical viewpoint made our studies too abstract and detracted from our conceptual understanding. 

For lab experiments, if we had had a powerful, reliable, and easy-to-use simulation tool instead of having to resort to trial and error, we could have achieved accurate designs on the simulator, thus reducing greatly the development and implementation time, not to mention achieving a much better outcome. 

When I was given a first-year electronics course to teach I thought that this would be the perfect experimental ground to try out my new approaches.

NI AWR University Program

Thanks to the NI AWR University Program, my students and I had access to cutting edge simulation software. NI supports teaching universities with NI AWR software donations for qualified programs. Eligibility is contingent on the use of NI AWR Design Environment™ products in a teaching environment, and available tools cover the full range of product offerings: linear, nonlinear, transient, electromagnetic, and system simulation engines, as well as full layout capabilities.

This enabled me to use Microwave Office circuit design software for my courses. In addition, because the program provides self-service licenses, my students were free to work when and where they wanted and were not tied to the lab. While Microwave Office is developed for high-frequency circuit design, it has also proved very suitable and useful for the simple analogue circuits that are taught in my first year course, which mainly focuses on operational amplifiers (op-amps), diodes, and their applications. 

While it is all well and good to tell the students that they can get a license for a very powerful and useful simulation tool, how do you actually get them to engage with it?

Innovative Teaching Methodology

I led by example and used the simulator in the lectures to show in a conceptual and dynamic fashion how varying the values of circuit elements and adding or removing elements affects the operation of various circuits. The students saw how easy and powerful the software was and they became very interested. In fact, some students realized how useful it would have been in subjects from the previous semester, such as linear circuits, and were almost resentful that they had only been shown this tool in the second term when I joined the faculty.

The other crucial element in getting first-year students to use a simulation tool was to make it very easy to get started by providing relevant and “easy-to-digest” training material and support. I therefore produced seven video tutorials, which illustrate how to use the tool for basic DC and AC circuits, as well as op-amp and diode circuits. I also regularly supplied simulation files to go with the lectures and pointed out in the notes what they could experiment with. Lastly, I organized weekly drop-in sessions when students could come and get help with their simulation endeavours.  

Out of a class of 95 students, nearly all registered on the NI AWR University Program website and created their own licenses. Students loved being able to use the simulator on their own PC and the fact that NI make this possible was a major factor in the success of the class. They also found the video tutorials very useful. In previous years they were given one three-hour session on how to use SPICE. This was lab-based and attendance was compulsory, but students would just come and do it because they had to, and then forget all about it. 

With the videos they could go through the training anywhere, anytime, and at their own pace.  They could also refer back to them again and again if they forgot how to do something. Also, thanks to self-licensing, they could then play around with the simulator whenever and wherever. Despite the fact that the use of simulation was optional for the unit, many used the simulator extensively and became regular users—not because they had to, but because they realized how much it could help them with their studies and with their future career. 

All of the students found the software useful and 62 percent gave it a five out of five. All of the students said they would like to see it used in other units. Comments from students included, “The tutorial was very enriching and was a quick way of learning a new software which was very useful during the course. Furthermore, the tutorial was useful because at any point in time we could refer to the videos and look at the part that was essential to us.” 

Simulation for Lab Experiment

In previous years students were also required to carry out a lab experiment, worth 20 percent of the unit, which entailed the design and characterization of a tuneable active filter for audio applications (Baxandall circuit). As a first step, they had to calculate values for resistors and capacitors which would allow them to achieve a specific frequency response. They used to spend time doing this during the lab session. Sometimes they got their values wrong and only realized it after they’d carried out the circuit characterisation, which meant that they had to repeat the whole experiment. 

1602 HFE teaching

Figure 1 • Home-lab kit. Note that the device at the top right hand corner is the centre-piece of this kit. It is a 2 channel USB oscilloscope which also comes with a signal generator.

I gave them the lab script before the lab experiment took place and encouraged them to carry out the calculations beforehand and verify the response of the resulting circuit with the simulator. They were also encouraged to play around with the circuit and gain a better understanding of how the circuit actually operated and achieved its filtering action. The average mark for the coursework was considerably higher than the previous year and their technical notes clearly demonstrated a much better conceptual understanding of how the circuit operated. 

The questions were designed in such a way that the solutions to the mathematical equations would yield values which were not in preferred values ranges for capacitors and resistors. The students therefore had to select either components with the closest possible value or use a combination. By using the simulator they were able to see what difference various values would make to the response of the circuit without having to spend time trying different values in the lab and measuring the frequency response for each variation manually. 

Students were also encouraged to model the mathematical equations and compare mathematical solutions and simulation results based on real models of op-amps and practical results. 

This method of learning is considerably richer not only in the content it delivers to students, but also in the skills they acquire, which allows them to explore their thoughts, ideas, and curiosity, getting much greater insight into the subjects that they are studying.

Compact Lab Kits

In addition to introducing Microwave Office and training videos, I also introduced compact home lab kits (Figure 1), which students could borrow to try out the lab experiments at home before the lab or repeat them afterwards. The students were also given access to a components cabinet, which allowed them to experiment with any circuits that they liked. The home kits were put together in such a way as to enable students to do pretty much everything that they could do in the lab at home.

I gave them two 9-V batteries as power supplies, a breadboard, a multimeter, a PicoScope 2204, which is a USB-powered oscilloscope and signal generator, and unlimited access to components (passives, op-amps, diodes, transistors). The fact that they could simulate the circuits before implementing them on a breadboard gave them much greater confidence about their home experiments. This is key, because without some degree of confidence that their circuit is going to work, they may be very tentative to implement it when there’s no academic around to ask.  

1602 HFE teaching

Figure 2 • Student feedback on video tutorials.

The home lab kits were just a trial this year, but since they were so popular we will be offering many more next year. One student commented, “What I liked most about the course was the ability to enjoy the experiment with no rush or fear of not getting it right the first time. Dr. Fornetti helped a lot to point my work in the right direction. I was glad that during the ‘real’ lab I felt a lot more confident than usual.”  Additional comments included:

  • Ability to sweep across frequency and see the change in output in real time.
  • Ability to show lots of measurements all at once + averages + standard deviations. 
  • Having the time to explore the topic beyond the scope of the lab test script and not having to work with a set group of people. 
  • I enjoyed being able to experiment with different components. It definitely complements the theory we have learnt in lectures. 
  • I had more time to understand what was happening and I also had the chance to build circuits not related to the experiment. 
  • I totally understand the whole experiment now and know how to connect the circuit up correctly, this is important because I always meet circuit connection mistakes during the previous lab. 
  • Ability to play around with the circuit without being pressed for time or not following the lab sheet - can experiment what happens with different component arrangements and values. 
  • Really enjoyed the ability to automate data acquisition and frequency sweeping easily and do a spectral analysis of it. 

Statistics show that almost one-third of the class took advantage of the ability to work at home.  

Feedback on using NI AWR Design Environment was very positive:

  • On--the--fly variable tuning is a very nice feature for experiments. Setting up circuits is a lot less fiddly than SPICE and the graphs generated are really useful. 
  • Being able to implement the circuits described in the lectures. 
  • Being able to simulate a circuit when I had doubts about my mathematical answer. 
  • The simplicity of being able to place and connect all the electronic components on screen and watch a displayed value given. 
  • That it is possible to model non-ideal behavior of components. In depth control of the plots. Modular layout (graphs, schematics. etc.). 
  • The program is a very good one which allows us to simulate everything before coming into the lab. Using this program, we can also compare the result at the end of each lab which helps us analyze our data and therefore give a better explanation of the data variation and fluctuation. It also helps us to implement different schematic diagram helping us to have a clear view of the problem. 

The innovative use of videos to demonstrate the techniques of simulation also received very positive feedback:

  • The video tutorials were useful and a good way to cover using tools-navigating the UI can be hard to explain via text. 
  • The tutorial was very enriching and was a quick way of learning a new software which was very useful during the course. Furthermore, the tutorial was useful because at any point in time we could refer to the videos and look at the part that was essential to us. The explanation provided in the video was clear and concise. 
  • The video tutorials were useful because you could pause/rewind at key points and I think software is best explained by demonstration. 
  • Very useful indeed! I get to rewatch it every time I forget about any steps to take to attain my required goal. 
  • Tutorial videos are certainly the best way to learn any GUI based software. It is easier and most importantly faster to learn this way, reading the manual would take more time to achieve the same depth of understanding the interface. 

Use of NI AWR Software in Other Units

Since NI AWR Design Environment and the Electronics 1 video tutorials were very popular with our first-year students, I strived to continue to support them as they got into their second year. To this end I produced two video tutorials to complement their Electronics 2 Large Signal Amplifier labs which, in previous years, had been criticised by students for the lack of simulation support. Unlike the Electronics 1 videos which were more general, these were bespoke to the lab exercises and illustrated in detail the operation and implementation of the Class-A and Class-B BJT amplifiers described in the Electronics 2 lab scripts.

The feedback from the students demonstrates that the video tutorials did not only provide appropriate guidance and support to students who already intended to use NI AWR Design Environment but also convinced those who were not so keen by demonstrating just how useful the simulator could be. This is shown in Figure 2.

The feedback also clearly shows that the video tutorials:

  • Helped students achieve a better understanding of the principles of operation of amplifier circuits (89 percent agree)
  • Saved them time in the lab by allowing them to prepare before-hand by simulating the circuits. (74 percent  agree)
  • Made their lab work easier, more enjoyable and less stressful (79 percent  agree)

More importantly students saw the benefits beyond the lab exercise and confirmed that the video tutorials and the simulator were also very useful to gain a better understanding of the material taught in the lectures. (79% agree).

One of the students said: 

“The video tutorials were great as they allowed us to get to grips with the lab beforehand, which made it less frantic and stressful in the labs themselves. They did not give us the answers, but gave us an idea of what the lab was about and what to expect, concurrent with the theory we are learning. The fact we had an idea of the lab before we went in also took pressure off the demonstrators, and allowed their time to be spent better on helping people understand theory rather than simply trying to get circuits to work. I would like these online videos to be available for every lab we have!”

Conclusion

The great thing about NI AWR Design Environment is that it is relevant and useful for very many subjects. I therefore intend to make it the standard simulation package for the entire degree course. Indeed students would like to see it used in other units and it has now been introduced to the Linear Circuits and Electronics 2 units and will soon be introduced to Electronics 3. We also plan to introduce NI AWR Design Environment Visual System Simulator™ (VSS) to units on communications.

Clearly video tutorials are a great way to go. This is also corroborated by the popularity of my book, Conquer Radio Frequency: A Multimedia Conceptual Guide to RF & Microwave Engineering, Based on AWR Microwave Office Video Tutorials and explore my YouTube channel: https://www.youtube.com/user/RFMicrowave.

In light of this, next year we will be giving free access to the online version of Conquer Radio Frequency to all microwave and RF engineering students at the University of Bristol. 

My main goal is not to indoctrinate but to promote active, student-led learning. There is a syllabus and there are notes and equations to be learned, but I want to enable students to expand their learning beyond the syllabus and follow their own interests and ideas. I want them to be able to experiment and create and have all the tools necessary to take a front line role in deciding which paths to follow through their journey in the fascinating world of electronics. 

About the Author

Dr. Fornetti is currently a Teaching Fellow at the Department of Electrical and Electronic Engineering of the University of Bristol, where he concentrates his efforts on enhancing the students’ learning experience by improving and modernizing courses contents and teaching methods. Dr. Fornetti has also worked in the industry as a control systems engineer at Rolls-Royce civil aviation division, as an RF engineer at Motorola Networks, and as a consultant at The Technology Partnership.

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Insulated Wire Inc.

Insulated Wire Inc. is pleased to announce that following the retirement of a French delegate, IW Microwave Products Division President, John Morelli, has been appointed as the Secretary for IEC/SC46F, a subcommittee of IEC/TC46. IEC/SC46F is responsible for RF and Microwave Connectors and Components International Standardization.

Mr. Morelli, who is sponsored by Insulated Wire, brings significant RF/Microwave connector and component experience to the position, and we congratulate him on his new appointment. Mr. Morelli had been serving as the chief Technical Advisor for the US National Committee’s Technical Advisory Group to IEC/SC46F.

The US National Committee of the IEC is a fully integrated entity of the American National Standards Institute (ANSI).