Analysis of the Degree of Practically Achievable Superdirectivity using Poynting Streamline Method

Streamlines of Poynting vector fields and antenna effective area shapes provide a unique way to understand the physics of a receiving superdirective antenna. Superdirectivity is implemented by expanding the effective area shape from the border of the antenna physical aperture. Considering using a resonant structure in font of an aperture antenna, under the same resonant element density, the expanded distance of the effective area shape keeps the same for different antenna aperture sizes and shapes. Based on this assumption, superdirectivity is practical for electrically small and middle size antennas and electrically large antennas with a large aspect ratio. A superdirective horn antenna with 115% aperture efficiency was experimentally demonstrated.