Far-Field Radiation Patterns of Terahertz Wire Waveguides

A formula for describing far-field radiation properties of metal wire waveguides is derived based on the Fresnel-Huygens diffraction theory. According to the formula, we find that the far-field patterns are the same for waveguides with different metal materials, and the amplitude of the electric field is in inverse proportion to the radiation distance. Furthermore, the far-field radiation properties versus the terahertz (THz) wave frequency and versus the metal wire diameter are investigated. Finally, we demonstrate that direction angles and shapes of the radiation lobes can be changed by using diaphragms with different aperture sizes.