There are digital systems and sensor devices with ultra low
power consumptions for energy harvesting purposes [1]. This
makes feasible the development of low power harvesting
systems. Research work have been conducted on
electromagnetic energy scavenging on high frequencies, from
2GHz to 18GHz, the unlicensed 2.4GHz and 5.8GHz ISM
band [2][3]. Also, technologies such as RFID use similar
technology to work at 13.56MHz or UFH-ISM frequencies
[4][5][6]. Most of them use their own RF transmitter to
supply power. In addition, the distance between the RF
transmitter and the harvesting unit is relatively short [7]. And
in the ISM band, the transmitted power allowed is low.