A compact normal-mode VHF/UHF dual-band helical antenna for lunar microsatellite

This paper has proposed a novel compact VHF/UHF dual-band helical antenna, which was used onboard Longjiang-2, the first independent Earth-Moon-transfer microsatellite. As a critical component of the first amateur radio communication system for a lunar satellite, the antenna requires small size and omnidirectional beam coverage. The structure of the resulted antenna is a combination of a helix and a loaded monopole, and has achieved a 56% size reduction for axial height compared to a conventional normal-mode helical antenna. Moreover, parametric studies were performed to explore the resonant characteristics. The radiation patterns of the proposed antenna installed on the satellite were simulated, which indicated that the antenna achieved a good beam coverage of more than 99.9% in space. Measurements in anechoic chamber and in lunar orbit were carried out to verify the effectiveness of the design.