As these levels decrease when withdrawing from the center, it seems that the most severe norms (0.01 mW/cm2 after the Russian norms) are respected as soon as one is out of the reception site, that is beyond a 3.5 km wide ring surrounding the rectenna. III. CRITICISM OF THE HYPOTHESES FOR CALCULATING THE PATTERN The computations which gave the results suppose that the illumination law of the transmitting antenna is exactly that foreseen as well for the amplitude as for the phase. Now there are different causes for disturbing this ideal law: 1. There is no doubt that the 105 klystrons or the IO6 amplitrons feeding the antenna will not provide exactly the same power. Moreover, a non-negligible percentage of these tubes may badly work or even break down. There comes out of it disturbances in the amplitude variation. 2. A phase locking device is foreseen in order that the phase of the field radiated by each of the elementary arrays may be the same. Here also, bad working or a breakdown of this device concerning a certain percentage of elementary arrays may cause phase distortions. 3. Lastly, a part of the antenna may be damaged by a mechanical or thermic cause. The disturbances of the transmitting antenna ideal illumination law might cause in the radiation pattern: - a broadening of the main lobe, which would cause a decrease in the efficiency of the microwave transmission since the spill-over of the beam radiated outside the rectenna would increase. - a growing in the level of the side lobes which might be perceived in possibly inhabited zones situated at some tens or hundreds kilometers from the reception site. This last drawback is, of course, capital, for if one or several side lobes cause a power density superior to the limit acceptable by humans the working of the station will have to be stopped. Of course, such stops would deliberate the main advantage of the SPS which is to be able to convert solar energy into electricity 24 hours a day all the year round. It is therefore very important to know already the influence on the radiation pattern of the SPS antenna: - of random variations in the amplitude and phase of the illumination law. - of the breakdown of a part of the antenna. For this, it will be necessary to take a model of the transmitting antenna illumination law incompatible with the hypotheses (equiphase and with revolution symmetry law) which had allowed to compute the radiation patterns studied in Sec. II after formula [1]. IV. METHOD FOR COMPUTING THE ACTUAL PATTERNS The field radiated by an aperture in the far zone (Fig. la) in P(R,0,t^) is given by
RkJQdWJsaXNoZXIy MTU5NjU0Mg==