A Compact RF Energy Harvesting System With an Improved Impedance Matching Network

This letter presents a compact RF energy harvesting (RFEH) system with an improved impedance matching network. The antenna includes a matching network consisting of periodic stubs, making it possible not only to adjust
$S_{11}$
when it changed due to fabrication errors but also to design the antenna to be more compact. We initially analyzed the effects of the fabrication errors and variations of
$S_{11}$
with respect to an adjustment of the matching network using an EM simulation. The antenna dimensions overall are 14.5 × 18.5
$\text{mm}^{\text{2}}$
, and it is integrated with an RFEH circuit consisting of a rectifier and power management unit, which compose the RFEH system. The proposed system was implemented, charging a load capacitor at the received power of −15 and −5 dBm; therefore, the proposed system with the impedance matching network contributes to compactness and can be utilized as the power source for compact Internet of Things sensors.