Dissertation Defence: Exploring Reflection and Absorption Mechanisms for Electromagnetic Shielding Using Printed Laminates
April 1 at 4:00 pm - 8:00 pm
Nibirh Jawad, supervised by Dr. Loïc Markley, will defend their dissertation titled “Exploring Reflection and Absorption Mechanisms for Electromagnetic Shielding Using Printed Laminates” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering.
An abstract for Nibirh Jawad’s dissertation is included below.
Examinations are open to all members of the campus community as well as the general public. Registration is not required for in-person exams.
ABSTRACT
Electromagnetic shields can be used to stop electromagnetic waves from propagating in a specific direction or to isolate a space from unwanted electromagnetic waves. It can be used to stop interference within communication signals, electromagnetic measurements, or electromagnetic devices.
In this thesis, we look at two methods of designing shielding for specific applications: one utilizing reflection and the other using absorption. For the reflection-based shielding, we use a technology called frequency selective surfaces (FSS), while for the absorption-based shielding, we use metasurfaces. Both the FSS and metasurface consists of periodic conductive elements drawn on top of a dielectric substrate.
The FSS-based shielding aims to produce a wallpaper that can block Wi-Fi waves from passing through its surface. To fabricate this Wi-Fi blocking wallpaper, an FSS must be modified to operate at the two Wi-Fi bands, while accommodating all environmental effects and fabrication tolerances that might alter its operation. We present the measurements required to quantify all the environmental effects and incorporate them into an FSS element design to produce a Wi-Fi blocking wallpaper that can block the 2.4 GHz and 5 GHz Wi-Fi bands with a -20 dB attenuation levels in real-world testing. We also present some design modifications to increase the efficiency of operation and reduce the cost of commercial production.
The metasurface-based shielding aims to produce a design method that can be used to enhance the absorption inside low-loss dielectrics. Typically, shielding made from lossy dielectrics needs to be bulky to completely absorb an incident wave. However, a metasurface can be designed to convert a normally incident wave to an oblique transmitted wave by a process called anomalous refraction. The oblique transmitted wave then travels a larger path length inside a thinner substrate and enhances the overall absorption. We present a method to analytically design an absorption-enhancing metasurface. The prototype designed using this method incorporates three layers of loaded copper wires on a 6 mm thick FR4 substrate using standard commercial printed circuit board fabrication and can absorb 98% of an incident wave at 10 GHz.
