Showcasing of Large-Scale EM Structure on Interior Office Wall

A thin and large-scale electromagnetic (EM) structure suitable for installing on interior office walls has been prototyped and tested. The structure is aimed at harvesting and converting ambient cellular signals to direct current (DC) power, such that it can be used as an energy source for low power Internet of Things (IoT) devices. The proposed EM structure consists of 32 antenna elements, 8 radio frequency (RF) power combiners and 8 rectifiers which are all printed on individual single-layer circuit boards, keeping an overall low-profile form factor. The total size of the demonstrated prototype structure is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$8 \lambda$</tex> by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3.5 \lambda$</tex>, where the target frequency is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{9 5 0 M H z}$</tex>. The measurement results show that a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$100 \mu \mathrm{F}$</tex> capacitor can be charged up from 2.33 V to 2.7 V in 67 minutes. The stored energy is sufficient for collecting environmental data and transmitting the data from sensor to central station or mobile phone.