This dissertation investigates the leaky wave properties of planar periodic corrugated metallic antennas with novel analysis and design techniques, as well as novel antennas of this type with improved farfield performance. For the first time, the dispersion analysis of one-dimensional corrugated metallic designs with gaps larger than half-wavelength is presented. A novel analytical periodic method based on a transverse resonance is developed. Additionally, a full-wave unit cell dispersion analysis tool and the matrix pencil method are employed for the leaky wave analysis of a standard corrugated design. The analytical calculation of the radiation patterns of a finite size antenna evaluates the leaky wave analysis when compared to simulated patterns. Subsequently, the improvement of the farfield performance of a practical corrugated antenna is achieved with novel antenna design techniques. The matching bandwidth of a corrugated antenna at the low THz spectrum is extended with the substitution of the typical subwavelength feeding aperture with an open-ended and, next, a tapered waveguide aperture. The 3-dB gain bandwidth of such an antenna at low THz is also enhanced, by introducing a dual-depth corrugation concept. A suitable leaky wave analysis reveals the expected characteristics of a finite size dual-depth antenna in the farfield region. Fabricated prototypes and measured results are available for the aforementioned proposed models. The final part of this thesis introduces new corrugation types at microwave frequencies towards the goal of antenna bandwidth enhancement. Such corrugations are able to produce on their own extraordinary radiation characteristics, namely flat high gain response, extended 3-dB bandwidth and improved radiation patterns
