ABSTRACT
Besides the aforementioned principles of power scavenging from
mechanical, thermal, or solar energy source, this chapter deals
with energy harvesting fromelectromagnetic fields. Radio frequency
power transmission, or so-called wireless power transmission, is
nowadays one of the main research topics among mobile device
manufacturers since it is expected to eliminate any cables and
connectors for powering or charging devices such as cell phones
and laptops. In fact, radio frequency transmission offers the
highest energy retrieval among all energy scavenging technologies.
Since apart from the sun no natural sources of electromagnetic
fields with sufficient energy exist, sources for generating and
radiating electromagnetic waveswith enough energy to empower an
electronic device over a certain distance are necessary. The sources
are normally intended to be used for power transmission only but
can also be sources of radio frequency data transmission systems
that offer enough power. The latter is becoming more and more
attractive, as the availability of wireless data transmission systems
increases. In any case, regulatory constraints regarding the use of
frequency bands and maximum radiated radio power have to be
considered.