FEA of a Typical C/Ku-Band Earth Station Antenna Foundation System

Soil structure interaction studies for C / Ku band Earth Antenna structure foundations are imperative by virtue of stringent Pointing Error (PE) and Tracking Error (TE) specifications (a few milli-degrees) for the antenna reflectors. For Tracking Antennas there are semi-resonance issues of the antenna holistic system with respect to antenna Servo frequencies. This paper highlights the estimation of relevant dynamic soil parameters, in situ, using MASW approach and the detailed soil-structure interaction studies and FE analysis of the foundation system for a typical 18.0 m dia C band & 13.5 m dia. Ku -band antennae respectively. FE analyses have been carried out for the operational wind speed to meet the PE specifications using NISA and COSMOS/M, commercial FEA packages. Analysis has also been carried out in the Eigen value domain for the simulated system of antenna mass along with the RCC raft and soil portion. The study brings out the importance of holistic analysis and influence of the soil parameters on the antenna behaviour. Important conclusions have been derived and novel techniques implemented in the design with a view to improve the soil parameters at the site of both the antennae in order to meet the stringent design specifications.