Among the exams scheduled for the course of Medical Engineering studies at the University of Rome Tor Vergata there is the course of Wireless Electromagnetics Technologies. The course provides the foundation for current and next generation wireless services, including radio and video transmission, radar tracking, mobile and personal communications, wireless sensor networks, wireless charging, radio frequency identification, and satellite links.
During the lessons I had the opportunity to participate in a seminar on antenna prototyping techniques. Furthermore, after a brief theoretical introduction, the seminar moved to the laboratory where I was able to touch the prototyping of a patch antenna.
Prototyping
The prototyping of antennas follows different paths. In this case we are talking about patch antennas consisting of a layer of conductive material placed on a substrate which, in addition to introducing and defining the irradiation, separates the antenna from the ground plane. The starting element is therefore the dielectric material in the medium.
The seminar focused on low cost and high replicability prototyping for which it takes as a reference the classic FR4 characterized by:
\begin{aligned}
\varepsilon_{F R 4}&=4.8 \\
\mu_{F R 4} &\cong 1 \\
\{\tan (\delta)\}_{F R 4}&=0.0260 \\
h_{F R 4}&=0.8 \mathrm{~mm}
\end{aligned}So the starting element is an FR4 sandwich with two copper layer.
Patch antenna
Patch antennas are a type of antennas made in an integrated form. They typically consist of a dielectric substrate on which a constituent radiative element is obtained from a sheet of conductive material and a second layer which acts as a ground plane.
The radiation occurs due to the fringing phenomenon for which the electromagnetic field that is generated between the conductive element and the ground tends to bend at the edges and come out, going to radiate. This follows Balanis theory.
Milling machine
There are several numerically controlled techniques including engraving, 3D printing or milling. Milling uses very precise cutters that engrave and remove the conductive layer or cut the base in its thickness.
The exercise involves the construction of a 3.6 GHz resonant patch antenna powered by a microstrip. After the realization in CAD / CAE we moved on to the engraving of the base.
Resonance analysis
Subsequently, the antenna was made, and after having mounted the connector, it was tested to verify its performance.
