generated. Examples of optimal single beam and multiple (four) beam tapers are compared in Fig. 4 with the original 10 dB Gaussian reference taper. The optimum taper gives the vector amplitude for the electric field at each subarray or power module site. The vector phase angle is then calculated, compensating for the pathlength variations to the different rectennas from each power module in the antenna. The vectors from the rectennas are added, as would be done in each RF receiver, to form a composite vector which is unique for a particular subarray or power module. The composite vectors form the multiple beam amplitude/phase taper. For the computer analysis, the antenna is divided into either a 100 x 100 matrix representing large subarrays or power modules (approximately 13 m on a side) or a 300 x 300 matrix for small subarrays (4.2 m on each side). Although the 300 x 300 subarray matrix is more representative of an SPS antenna, the additional computations require significant run times on the Univac 1110 computers. The 100 x 100 matrix gives valid results except for antenna tilt conditions where degradations in beam performance due to operating off the subarray pattern boresight are magnified. THEORETICAL RESULTS Beam Patterns The ground beam pattern(s) for four multiple beams with the optimized taper in Fig. 4 are shown in Fig. 5. The main beam at each rectenna has a 23 mW/cm2
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