The Evolution From Metal Horns to Metahorns: The development of EM horns from their inception to the present day

The development of horn antennas is described from their inception in the 1890s to the present. Our main objective is to describe the advancement of their fundamental features, which are often driven by applications. The horn antennas discussed here were selected based on their significant concept advancements and are listed in chronological order within each class based on their first publication. Until the 1960s, only metal horns were used. In the 1970s, horns with dielectric loading were developed and resulted in several new and advanced horn designs. The latest renaissance in horn technology was fueled by the advent of metamaterials over the last 15 years, enabling horns with metasurfaces (metahorns) and horns with metalenses in particular. We now have air-filled, dielectric-loaded, and metamaterial-loaded horns; from inception, we have seen the transformation from metal horns to metahorns. More details will be supplied in the following sections.