composed of the same radiation modules as those of an antenna array with uniform polarization (Fig. 2), the modules being arranged as ring bands (Fig. lb). The electric field at the radiation module is uniformly polarized and the field amplitude at the modules in each band is constant. For a field with the above structure to be received one can use an antenna composed of receiving-rectifying modules arranged in a similar way. Preliminary analysis reveals a number of advantages to such a system over the MPTS with a uniformly polarized field at the antenna. Using radiation modules of 10-100 wavelengths (i. e. 1-10 m with a wavelength of 10 cm) the suggested arrangement allows the level of the antenna array diffraction (far) lobes to be reduced considerably, solving a serious problem with the SPS microwave power transmission system using uniform polarization [10], Also it should be noted that the axial symmetry (Fig. 1) eliminates the requirement for the receiving and the transmitting antennas to be mutually oriented in azimuth angle, which is important for antennas with uniform polarization (Fig. 2). What values of the collection efficiency will correspond to antennas with a radially polarized field? It can be shown that the maximum efficiency value, as in the case of uniform polarization, will provide a quadratic phase distribution focusing a beam at the center of the receiving antenna. In our paper the amplitude distributions providing the maximum value of collection efficiency between antennas with radial polarization were obtained [8]. Fig. 3 represents the maximum value of the collection efficiency and the transmitting and receiving antenna power coefficients Wa and Wr (the ratio of the average power density to the maximum power density) versus the wave parameter r for antennas with uniform and radial polarization [8].
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