The shielded spiral sheet antenna concept permits a small efficient antenna structure that is much smaller than the electromagnetic wavelength. In such small structures, the radiation usually goes almost all directions. A geometrical structure that shields the radiation from absorbers, and it directs the radiation in the opposite direction. This is difficult to achieve in very small radiators. At the same time, the shielded spiral sheet structure is more efficient than other antennas. Its radiation is shielded from an adjacent absorber by an asymmetric metallic border. The specifications of the asymmetric metallic border are given by an operational mathematical procedure.