The electric-field components parallel to the x, y and z-axes are shown in (a), (b) and (c), respectively. The intensity and phase distributions measured with the optical electric-field probe agreed with the calculated distributions very well, except for the intensity distribution of the electric field parallel to the zaxis and the phase distribution of the electric field parallel to the y-axis. In the intensity of the electric field parallel to the zaxis, asymmetric distributions were measured over the Vivaldi antenna and the radial balun, which was not observed in the simulation. The phase parallel to the y-axis could not be measured out of the circuit because the intensity of the electricfield radiating for the -x direction is too small to be detected with the calculated with the electric-field components parallel to optical electric-field probe, whereas the results fairly agree well on the planar circuit. These results indicate that near-field measurement using the metal-free electric-field probe is useful for intuitively diagnosing the radiation performance when designing antenna circuits.
EMC’14