Abstract:

A common problem arising in microwave and RF electronics undergraduate courses is the unavailability of simple fabrication techniques able to leverage “trial and error” teaching schemes. Simulation software can to some extent soften this problem, and, indeed, really interesting teaching approaches based on this alternative can be found in the literature [1,2]. However, the experimental competences of the students in high-frequency electronics can only be fully accomplished by allowing them to get in touch with physical circuitry, i.e. by themselves fabricating different kind of structures, contacting and grounding them, soldering small SMD (Surface Mounted Device) devices, etc.

In this context, cost becomes a key problem. In practical microwave syllabi, the laboratory equipment is extremely complex and expensive, e.g. vector network, spectrum and noise figure analyzers, microwave sources, etc. The fabrication of high-performance circuits, based on expensive substrates and with state-of-the-art prototyping technologies, is unaffordable and should be avoided in undergraduate courses, in which students learning, instead, is more effective and encouraging through a design-fabrication-characterization-redesign loop.

Some interesting experimental teaching alternatives have been proposed, e.g. in [3], the authors propose the employment of metallic tape to fabricate microstrip circuits, while in [4] a similar technique has been recently presented for a radar technology course. While this procedure is cheap, entertaining and certainly achieves good teaching results, it lacks, in our opinion, of sufficient reproducibility and it is not appropriate for the fabrication of other transmission lines such as microstrip or SIW (Substrate Integrated Waveguide).

In this work, we propose a quick and cheap prototyping approach based on the Voltera V-One. This equipment is commonly used for rapid prototyping in low-frequency circuits research, but is still able to provide reasonable performance in simple (teaching level) medium frequency circuits. Its operation is based on the disposal of conductive ink, following a path defined by the user through common techniques (e.g., Gerber/Drill files). The combined use with Keysight Pathwave ADS (Advanced Design Software) [5] and with a basic VNA-based (Vector Network Analyzer) characterization laboratory, allows our students to proceed with a complete design loop, useful for the demonstration of concepts such as microwave filtering, duplexing, amplification and calibration. To reduce costs, relatively low frequency values (around 1 GHz) are considered in the designs, allowing the fabrication with basic FR4 one-layer metalized substrates.

References:
[1] W. Hoefer, P. So, A time-domain virtual electromagnetics laboratory for microwave engineering education, IEEE TMTT, 51, 4, 2003.
[2] F. G. Ruiz, N. Rodriguez, D. Coronado, I. M. Tienda-Luna, L. Donetti, C. Sampedro, K. Caballero, Autonomous education in microwave and RF subjects: development of home-made software, Edulearn Proceedings, 1118-1125, 2010.
[3] S. Hum and M. Okoniewski, A low-cost hands-on laboratory for an undergraduate microwave course, IEEE Antennas and Propagation Magazine, 49, 3, 2007.
[4] M. Dwyer and D. Ricketts, The NCSU Rabbit Radar: Build a frequency-modulated continuous-wave radar in a day, IEEE Microwave Magazine, 21, 5, 2020.
[5] Online: https://www.keysight.com/es/en/products/software/pathwave-design-software/pathwave-advanced-design-system.html

Keywords:

Engineering, teaching, robot, microwave, telecommunications, electronics, circuits.