Prospect of 40–170GHz band spherical antenna

In this paper, the feasibility of a spherical antenna has been conducted by simulation. First, a basic model for spherical antenna is made, which consists of a 10 mm-dia sphere and a 600 mm-dia disk. It is shown that the surface current on the sphere is unidirectional, propagating from the feeding point to the zenith. The broadband feature is considered to originate in the nature of traveling wave antenna. Second, the length of the sphere stem, which is extended the coaxial lead to the sphere, is varied, and at 1.4 mm the maximum bandwidth of 5.1-22 GHz. Third, as a recent result the spherical antenna using a thicker stem gives broader bandwidth of 5.2-39.5 GHz. Finally, the structure is reduced by one-eighth, resulting in 40-320 GHz. The radiation pattern in azimuth angle is omnidirectional, and the gain is 3.1 dBi at 50 GHz, 4.9 dBi at 100 GHz and 4.2 dBi at 200 GHz.