Energy and the environment have both become a matter of concern among
researchers worldwide. There are several forms of energy present in the environment;
therefore, utilizing these resources is preferred. In the modern world, the evolution of
energy harvesting has received a lot of attention. Various energy harvesting topologies
like solar, vibrational, piezoelectric, RF (radio frequency), etc., are available, but RF
energy harvesting has a bright future in generating a small amount of electric power
that drives various power-constrained electronic devices due to its easy availability and
self-sustainability. The circuitry, which converts RF energy into DC output, is termed
the rectenna unit of the model. The rectenna unit consists of receiving antenna followed
by the matching network and rectifier. The aim of this chapter is to provide a detailed
review of various technical aspects of radio frequency energy harvesting, which have
been showing a great proliferation in the designing of the RF energy harvesting model.
Comparative analysis of different topologies of each aspect is also performed.