RF energy harvesting mechanisms can be primarily classi-
fied as ambient RF energy harvesting and controlled RF energy
harvesting. Ambient RF energy harvesting systems convert
ambient RF signals such as digital TV broadcasting, cellular
Base Transceiver Station (BTS), and ambient Wi-Fi radio
waves into electrical energy to power RFIDs and sensor nodes.
However, controlled RF energy harvesting systems use dedicated
energy transmitters (i.e. wireless chargers) to generate
and transfer RF waves with deliberate power intensity. Parks
et al. [15] demonstrated a sensor node harvesting ambient
RF energy from both digital TV and cellular radio waves
that operates at a distance of 10.4 km from a 1 MW UHF
television broadcast tower, and over 200 m from a cellular
base transceiver station. An ambient RF energy scavenger that
harvest the RF power of a TV signal through an inkjet-printed
dipole antenna and a charge pump was shown in [16] and
[17]. The multi-channel OFDM nature of TV signals has been
exploited in [2] for powering an embedded microcontroller.
Shigeta et al. [18] introduced a capacitor-leakage-aware duty
cycle control method for sensor nodes powered with digital
TV broadcasting signal waves, which captures the long-term
and short-term fluctuations of TV signals due to the scheduled
facility. Dolgov et al. [19] designed a power management
system for online low power RF energy harvesting of ambient
cellular waves from the BTS. Moreover, Olgun et al. [20]
developed a technique to harvest ambient Wi-Fi radio waves
at 2.45 GHz for powering a temperature and humidity sensor
with a LCD.