Figure 10.2.9 Beam Cone This angle can be estimated using the following equation: where Thus the diameter of the spot on the target will be [] when taking into account the beaming distance R = 80 m. We obtain the directivity D and the gain G of the antenna using the following relations: According to the definition of the angle [] the antenna gain on the surface of the half gain cone will be: Then we consider the power density on a rectenna within the distance R of an isotropic transmission antenna to be: where [] is emitted power [] here = [] Finally we obtain the power density of the real antenna on the target on the surface of the half gain cone: Considering a rectenna of 2x2 m^2, a power density of 0.0752 W/m^2 is obtained on the rectenna for each watt emitted by the transmitting antenna, which can be interpreted as a beaming efficiency of 7.5%. This value represents a worst case estimate. Actually the power density on the rectenna will be higher than on the surface of the half gain cone. Thus for an ideally pointed beam the efficiency could go up to about 15%.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==