Design objects and limitations of antenna for VSAT and USAT earth station

In this paper，antenna aperture division and equivalent diameter calculation are described simply for very small apreture terminal (VSAT) and ultra small aperture terminal (USAT) earth station antenna.Design objects of VSAT and USAT earth station antenna introduced systematically，side-lobe characteristic of antenna pattern，cross polarization characteristic of antenna，and characteristic of offaxis equivalent isotropically radiated power (EIRP).Limitations of design objects are pointed for VSAT and USAT earth station antennas，and recommendation of antenna pattern first side-lobe level request is put forward for VSAT and USAT earth station.