Multiple beams can therefore be created by using an antenna illumination function which is the complex sum of the individual beam illumination tapers. In the SPS antenna, the electronics proposed for phasing a single beam could be adapted to process multiple beams although the complexity would be increased. The pilot beam signal from each rectenna would have a unique pseudonoise code for identification. The RF receiver in each power module or subarray would simultaneously receive and process each pilot beam signal. The vector addition of these signals would be used for phasing the power tube(s) associated with the RF receiver. SUBARRAY EFFECTS AND GRATING LOBES The multiple beams are scaled by the subarray pattern factor, E„.s/A, and small losses occur because the subarrays (or power modules) cannot be pointed directly at the rectennas. As an example, for rectangular subarrays of dimensions, Lx and Ly, the ground pattern for a single subarray is (5, Eq. 25) Grating lobe effects also need to be considered since the array pattern, E„.array, in Eq. 8 gives a concentrated peak at the mainbeam location (rectenna) and equivalent peaks at each grating lobe location. The array pattern (for the simple case of uniform illumination) may be written (5, Eq. 29)
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