The present invention relates to an antenna system mounted on a mobile vehicle. In the present invention, a power distributor and a part of a high-frequency module that includes a frequency converter are placed in an external fixed unit that is placed outside a radome. In addition, an active cooler/cooling fin, a heater, and an air circulation fan are placed at an internal bottom plane of the antenna system, and a cooling fin and cooling fan are placed at an external bottom plane of the antenna system.