a traveling-wave antenna in which the phase velocity of an electromagnetic wave propagating along the antenna is less than the phase velocity of a plane wave propagating in free space; in addition, the strength of the field in the direction normal to the antenna decreases exponentially (such a wave is called a surface wave).
The delay structure of a surface-wave antenna is made in the form of a ribbed metallic surface or a plane metallic surface covered with a dielectric layer. The surface wave is usually excited with a horn antenna or an electric dipole. The major advantage of such an antenna is that it can be constructed in the form of an insert that barely projects from the supporting surface; this is of great importance in installations on aircraft. Surface-wave antennas are used chiefly in radio equipment that operates at centimetric and decimetric wavelengths.