UBC Theses and Dissertations

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UBC Theses and Dissertations

Single-layer dual-wide-band frequency selective surfaces for Wi-Fi blocking in the built environment Jawad, Nibirh


The use of Wi-Fi networks to access the information on the internet has seen a phenomenal increase in recent times. With the large volume of traffic being transmitted, the amount of confidential information has also increased. Yet access to Wi-Fi networks is only secured through password protection. An improvement in technology used to gain unauthorized access has lead to a concern over information security. One possible way of providing increased security to the Wi-Fi networks is by physically limiting the network to a fixed space. Wi-Fi signals can be contained to a built environment through the use of frequency selective surfaces (FSS) in the form of a Wi-Fi blocking wallpaper. An FSS is a conductive periodic pattern in a 2D array. It is able to selectively block or pass electromagnetic waves. Through careful design it should be possible to produce an FSS which is able to block the two Wi-Fi communication bands. In this thesis we present a analysis of various band stop FSS to reach a design with a high stop band bandwidth. We then modify the design to produce a second stop band at a higher frequency. The two stop bands are designed to be at the same ratio as the Wi-Fi communication bands. Two of the designs are fabricated to verify the performance in experiment. The presence of dielectric substrates and the incident angle of waves are known to modify the performance of FSS. Experiments are carried out to quantify these effects and compensate for them in simulations. A simulation method is developed which can closely predict the performance of the design under real-world conditions. The design with the best performance out of the simulated dual band-stop structures is the interdigitated double hexapole and it shows a -20 dB bandwidth of 24.75% and 10.5% in the first and second stop bands respectively. It is able to cover the entire Wi-Fi spectrum giving a minimum attenuation of -34.1 dB across the 2.4 GHz and -29.24 dB across the 5 GHz Wi-Fi band at normal incidence.

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