| Popis: |
It has been shown previously that a symmetric antenna such as a dipole driven via a balun from a coaxial transmission line can be represented as a 3-terminal, 2-port network and that for vertically-polarized antennas operated near ground this network is asymmetric. An experimental approach for the determination of the values of the elements in this network representation has also previously been given. Although reasonably good agreement between simulation and experiment was obtained, the experimental procedure required three 1-port measurements and could not accommodate full error correction in the vector network analyzer (VNA) calibration. Therefore, we consider an alternative experimental approach for determining the network components of the 2-port antenna model. The new approach involves connecting both ports of the antenna simultaneously to the 2-port VNA via a dual coaxial cable and fully exploits the capabilities of a VNA including calibration and adapter removal. Both approaches are presented in detail and compared. Finally, the effect of ferrite choke beads on the coaxial feed transmission line on the equivalent network is investigated. |
