Analytical approaches for nano-plasmonic and micro-millimetric antennas

Antenna modelling approaches, based on suitable spherical harmonic expansions of the radiated electromagnetic field, are addressed and thoroughly investigated. Particular emphasis is put on the simultaneous transverse resonance diffraction (STRD) technique for plasmonic antennas. This method efficiently allows evaluation of the near-field distribution because of the interaction of optical sources, such as surface plasmon waves, with perfectly conducting wedges. The STRD technique based on the multipole expansion of Green´s function (MEG) is particularly suitable for the design and rigorous analysis of wireless nano-systems. On the other hand, the characterisation of electromagnetic radiation processes in millimetric/micrometric short-pulse electrical antennas can be conveniently carried out by means of the dedicated singularity-expansion-method(SEM)-based methodology detailed in the second part of this study. Together, the proposed new analytical approaches provide a powerful and complete tool for small antenna design GHz and THz frequency ranges.