Wave propagation in planar antennas at THz frequencies

Waves along metals at an air-dielectric interface tend to propagate at a velocity that is intermediate between the velocity of waves in the air and the velocity of waves in the dielectric; at frequencies below a few GHz the quasistatic approximation to the effective permittivity can be used to find the effective wavelength that propagates in the antenna. Above these frequencies the frequency dispersion of the effective permittivity must be taken into account. In order to find the effective permittivity and the effective wavelength of propagation at THz frequencies a numerical simulation of a planar dipole antenna is performed and compared to measurements made on similar devices. From the numerical results an empirical formula for the effective permittivity is obtained which accounts for the effect of the complex surface impedance of metals at THz frequencies.