\chapter{Introduction}

In our lifes we use many communication technologies that work over a short range: for connecting our mice and keyboards to our computers, listening to music wirelessly and to pay contactlessly. Those tecnologies include but are not limited to: Bluetooth, RFID, NFC and many others.

What many of those technologies have in common is that they work on top of radio waves that utilize electromagnetic induction. One of the problems of radio wave is the difficulty of passing through conductive materials such as water or metals. \cite{RadioWaves}
