this antenna. A board shows, for each of these laws, the total power radiated by an antenna of a given radius. We can notice that the uniform illumination law allows the largest power radiated for the smallest aperture. On the contrary, for tapered illumination laws, the radius of the transmitting antenna must be all the bigger as the level of the illumination law on the edges of the aperture is smaller. In spite of that, the increase of the radius does not prevent a slight decrease of the power radiated. Figure 3 [after (1)] shows the radiation patterns corresponding to those different laws. In order to compare them to one another, the level is normalized, in all cases, to 0 dB in the axis. For each of these laws, a board shows which is the percentage of the total power which is kept in the main lobe. Choice of the Optimal Illumination Law The illumination law of the transmitting antenna must be chosen after three criteria: 1. The obtaining of the largest possible ratio between the power radiated and the diameter of the antenna. 2. To keep in the main lobe a maximal percentage of the total power radiated. 3. To have the lowest possible level of the side lobes. There is no illumination law which can at the same time answer these criteria. Indeed,
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