5:15 PM - 6:30 PM
[PEM18-P15] Low frequency characteristics of a wire antenna with noise reduction shield
Keywords:wire antenna, effective length, rheometry experiment, noise reduction shield, satellite, quasi-electrostatic field
In this study, we analyzed the effect of a noise reduction shield in order to elucidate the effect of such an antenna structure further. In the many cases of actual satellite, the spacecraft body and near the base of wire are shielded, to prevent the antenna from being affected on its sensitivity by the artificial noise generated inside of the satellite. Therefore, we performed experiments for shielded wire antennas to analyze the frequency characteristics of the effective length.
According to the results of the experiments, we found that the output voltage becomes small compared to the case of non-shield one, when the frequency becomes higher. As the cause, there are two possible factors. One is the distortion of the potential distribution around the satellite which is caused by the shield. The other is the capacitance between the shield and the core wire. In order to analyze quantitatively, we analyzed potential distribution by computer simulations and calculated the output voltage theoretically by the equivalent circuit. As a result of simulation, we found that the potential distribution in the vicinity of the wire is non-linear, that is different from the linear distribution of the non-shield. And next, we made a theoretical calculation applying the potential distribution, which is the result of the simulation, to the equivalent circuit that includes the effect of the capacitance due to shield. Comparing the calculation result to the experimental results, the transition frequency in which the value of the effective length changes is very much consistent, and the difference of the output voltage value is below a few percent at all frequencies. From these results, it was clear that the capacitance between the shield and the core wire affects the impedance of the antenna, and it is the cause of decay of the output voltage when the frequency is high.
In our presentation, we will report the results of the experimental, the simulation and theoretical calculation in detail.