The studies of low-frequency discharge current oscillation phenomena in the 20 kHz range causing a deterioration of propulsive efficiency and operational instability are important to improve Hall thruster performance. A possibility that the amplitude of 20 kHz-range oscillation could be controlled by changing ionization-zone length was predicted in our previous work, based on experiments and theoretical analyses. 1) In this paper, the physical mechanisms of the ionization process in the acceleration channel are studied by using an unsteady one-dimensional numerical analysis; the methods of controlling oscillation amplitude are concretely discussed from the viewpoint of ionization-zone length. The numerical code generated in the present study would be an effective tool for the best design of a Hall thruster.

Abstract:In recent years, MIMO technology which uses multiple antennas has been introduced in mobile terminal to increase communication capacity. However, if MIMO antennas are put closely, a strong mutual coupling occurred. Then it causes decreasing radiation efficiency and channel capacity. Therefore, reducing the mutual coupling is required. In previous study, connecting MIMO antennas by inductor L or added branch elements to antennas instead of L. In this paper, we propose a novel decoupling method by using a short stub and confirm that proposed model performed decoupling, increased radiation efficiency.

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