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Rectenna
Microwave power transfer and DC conversion fulfills the necessity of
integration to the environment at a relatively low implementation cost. One of
the most important and the main requirement of a WPT system is the efficient
transfer of electric power. The overall DC (or RF) to DC efficiency of the
WPT system characterizes this performance criterion. The rectenna, the
rectifying circuit integrated with an antenna, is the key component in
determining the efficiency in WPT,
The rectenna is based on two parts: an antenna that receives a
microwave signal and a rectifying circuit that converts the microwave signal
into a DC voltage at the output. One of the most important characteristics of
a rectenna is its efficiency, which relates the DC output power to the input ac
power. Recently, rectenna designs for applications in wireless power transfer
and RF power harvesting were reported.
There has been some research involving microwave power
transmission for getting power to communities without wires. The idea of
wireless power transfer came from Nikola Tesla at the turn of the twentieth
century when he made a tower to transfer power without wires.
In 1977, Brown, at the Raytheon Company, achieved the highest
conversion efficiency ever recorded at that time for rectennas. He used a
GaAs-Pt Schottky barrier diode, aluminum bar dipole, and a transmission line
in the design. The conversion efficiency reached 90% at an input microwave
power of 8 W.