Power Transfer in the Fresnel Zone at Mm-Wavelengths

The power transfer efficiency(ratio of received to transmitted power) between two elliptical antennas in the Fresnel zone is investigated experimentally. The design procedure for an optimum power transfer system is analyzed. Pyramidal horns in the foci of the ellipsoids enable an optimum phase illumination. Deviations from a Gaussian amplitude illumination (which is close to the optimum) cause a significant decrease of the efficiency, which however is still larger than it would be for a guided or a free path transmission in the far-field of two antennas.