Spherical dipole antenna using optical/electrical converter

Abstract

AbstractA spherical dipole antenna is studied as a standard electromagnetic emission source in the EMI measurement. Its radiation characteristics are discussed both theoretically and experimentally. One of the antenna elements of a spherical dipole antenna is constructed in the shape of a shield case in which the electronic circuit is installed. Hence, the electromagnetic analysis can be carried out without considering the shape of the electronic circuit into the boundary of the analysis. It is pointed out that the electromagnetic field in not only the far region but in the near region can be computed numerically with high accuracy by means of the mode matching technique.By using a nonmetallic optical fiber instead of a coaxial cable as the signal line, the disturbance of the electromagnetic field by the cable can be neglected. Based on the numerical results, a spherical dipole antenna was fabricated and the radiation characteristics were measured at 30 to 1000 MHz. It was confirmed that the measured data and the numerical results agree within 1.9 dB for the vertical polarization and 1.7 dB for the horizontal polarization. From these results, it is clear that a spherical dipole with radiation characteristics as numerically computed can be realized.