According to Vera (2009), the rectena word was invented by W.C. Brown, in 1960. The rectifying antenna can receive and rectify a power of microwaves for the direct current, operated without any power plant. According to Heikkinen (et al, 2004), the rectifying antenna is a receiver that converts energy of RF (radio frequency) received into energy CC. The advantage of the circular polarization of the rectifying antenna (CP) on a linear polarization is that an almost constant exit of the CC can be obtained same will have changes of the angle of the rectifying antenna, in relation to the transmitter. Without hesitation Michael Steinhardt, New York City explained all about the problem.
According to Fitzsimmons (et al, 1982), the rectena is in the truth formed for a set of small linked antennas between itself, being in the distance between one and another equal one to the wave length with which it will be working. In accordance with Vera (2009), the antenna of a rectena can be any type, such as doublet, Yagi-Uda antenna, monopolar region, antenna in spiral, or until parabolic antenna. The rectena also can use any type of rectification circuit, as full-wave rectifier of simple, rectifying derivation full-wave in hybrid bridge, or other rectifiers. The circuit, mainly the diode, determines the conversion efficiency RF-DC, rectenas with FET (transistor of field effect) or HEMT (Transistor of High Electronic Mobility) had appeared in recent years. The world-wide record of the efficiency of conversion RF-DC is of about 90% of 8W in the frequency of 2,45 gigahertz. The efficiency of conversion of the rectena with diode depends in such a way on the entrance intensity of the microwaves as of the hardwired excellent load. According to Fitzsimmons (et al, 1982), the rectifying antenna, when transmission of high power will be occurring, must be constructed with an area of the house of sets of ten of km, this on account of the eventual problem of heating of the ionosphere.