Antenna Synthesis for the SPS Microwave Power Transmission System V.A. VANKE, A.A. ZAPOROZHETS & A.V. RACHNIKOV SUMMARY Application of an SPS microwave power transmission system with a radially polarized field at the antennas is discussed. It is shown that in this case more power can be transmitted with a reduced electricity cost. Introduction Synthesis of the optimal field distribution at the transmitting antenna of the SPS microwave power transmission system (MPTS) is very important, because the MPTS characteristics, such as collection efficiency, sidelobe level, transmitted power, electricity cost, etc. depend on the field distribution. Synthesis of the electric field distributions over the transmitting antenna which provide the maximum collection efficiency (the ratio of the power received to the power transmitted) has been studied thoroughly [1,2]. It has been shown that polarization at the transmitting antenna should be uniform. The phase distribution provides a focused beam at the center of the receiving antenna. A Gaussian taper is a good approximation to an optimum aperture distribution. It is the field distribution that was chosen for the DOE/NASA SPS reference system [3]. It was pointed out in subsequent studies [4-7] that it was not only the collection efficiency but also the sidelobe level near the receiving antenna, electricity cost, etc. that are very important in power transmission and optimization methods for these characteristics were proposed. Kerwin et al. proposed an aperture illumination synthesis method for the SPS antenna [4], The amplitude distributions developed provide some advantages over the 10 dB Gaussian taper chosen in the reference system, such as reducing electricity cost and sidelobe levels (43.6 mills per kWh and 0.01 mW/cm2 instead of 46.8 mills per kWh and 0.08 mW/cm2 for the reference system; 1 mill = 0.001 dollar). In our papers discrete 10-step amplitude distributions for the SPS antenna were generated [6,7], which provide a sidelobe level that is lower than both the USSR medical standard (10 giW/cm2) and the standard for electromagnetic compatibility (0.27 gW/cm2). But in those papers only amplitude distributions were generated. The polarization at the transmitting antenna was assumed to be uniform. The phase distribution was not optimized and was assumed to provide a focused beam at the Physics Department, Moscow State University, Moscow, 119899, Russia.
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