Based on the uniform geometric diffraction theory method the asymptotic solutions are obtained for 3-D problems of diffraction of the fields radiated by the arbitrary oriented electric dipole Hertz and half-wave resonant vibrator on the thin ideally conducting plane screen of the rectangular form and on the finite size corner reflectors of a various configuration. The carried out experiments confirm the accuracy of calculated radiation patterns of analyzed systems. There are also calculated the optimal tilt angles, positions of the vibrator, placed above the rectangular screen, and the reflector dimensions for producing the circularly polarized radiation in the main observation planes with maximum directive gains.