| （英） |
It is well known that the unbalanced mode current flows on the outer conductor of the coaxial line, which is connected and fed to the antenna under test (AUT). In practice, the solution is to insert the ``balun'' at the feeding part. Conversely, until now, there has been little studies of quantitatively analyzing the excited ratio of the unbalanced mode to the balanced mode. So, the authors have proposed and evaluated the balanced and unbalanced mode analysis for the symmetric AUTs by introducing the mixed mode S parameters. And, the practical feeding in the balanced mode is simulated by using 180 deg. 3 dB hybrid coupler and the power ratio of the unbalanced mode to the balanced mode is also evaluated. In this report, the above analysis is extended to deal with the asymmetric AUTs. As a result, it is clear that the coupling between the balanced and unbalanced modes dominantly causes the existence of the unbalanced mode current. |