Application of the surface-charge distribution method to the interpretation of impedance measurements of a rocket-borne dipole antenna

摘要

In a companion paper [Béghin and Kolesnikova, this issue], we have presented the surface charge-distribution (SCD) method for modeling a complex devices's behavior in the radio frequency range around the plasma resonance. Here we give one application of this method to the interpretation of published experimental data of a sounding rocket experiment which was carefully designed to make the impedance measurements of a dipole antenna. The data were found by the authors of this experiment to agree generally well with theoretical predictions, including a hydrodynamic model for the ion sheath, except for a strong discrepancy in the antenna resistance below the plasma frequency. Using the SCD approach, which allows the determination of the charge distribution not only on the antenna itself but also on the rocket body, we show that the data can be remarkably well explained by feed end effects involving the gap region between the antenna and the rocket body. While these effects exist with the simple approach of mesh surfaces, the presence of an ion sheath is proved to magnify the mechanism. Thus we argue that the above discrepancy was due basically to the usual assumption of a triangular current distribution along the antenna.