FDTD analysis of reduced size substrate lens antennas

The input impedance and far-field radiation patterns of reduced size extended hemispherical lenses (fed by aperture-coupled microstrip patch antennas) have been investigated in the 47-50 GHz band, using the finite-difference time-domain (FDTD) technique. Good focusing capabilities and very interesting surface efficiencies have been found for some electrically small lenses. The effects of internal reflections have been quantified both in time and frequency domains. Diffraction and possible resonance effects have also been taken into account for an accurate analysis of radiating structures whose size is comparable to the operating wavelength.