Radome crosspolarisation on Intelsat standard ´A´ communication satellite antennas

The reduction in size of Intelsat standard ´A´ satellite communication antennas from 30.5 m to 15 m in diameter has necessitated the computation of depolarisation effects when the smaller antennas employ metal and dielectric space frame radomes for hardening and protection. Using the standard 15 m antennas enclosed by appropriately scaled-down metal and dielectric space frame radomes, the crosspolar discrimination (XPD) and the boresight shift (BS) have been computed close to antenna axis at 4 and 6 GHz. Comparison with the larger 30.5 m antennas enclosed by 45 m radomes have been made. It is reported that within 0.1 degrees of antenna boresight, the XPD introduced by the radomes does not exceed 33.0 dB as the worst case at 4 GHz. In particular, the Intelsat Specification of 30.7 dB for the XPD within the antenna´s tracking beamwidth in clear weather conditions for frequency re-use satellite communication systems is satisfied. The BS is negligibly low.