Space and frequency correlation characteristics of L-band multipath fading due to sea surface reflection

When maritime satellite communication is conducted at low elevation angles, fading due to sea surface reflection becomes a problem. For suppression of the fading, space diversity and frequency diversity may be employed. The correlation characteristics of multipath fading due to sea reflection in the spatial and frequency domains in L-band operation are studied. This is important in investigating the diversity effect. First, from the theoretical model of sea surface reflection, the correlation scattering cross sections of the coherent and incoherent components of the reflected waves are obtained. Next, from numerical calculations, the correlation characteristics are obtained with the antenna elevation angle and the height over the sea as the parameters. It is found that in space diversity good diversity effects can be expected from two antennas separated in the vertical direction by about 40 cm. It is found that in space diversity good diversity effects can be expected from two antennas separated in the vertical direction by about 40 cm. it is also seen that fading reduction cannot be expected with frequency diversity in the case of narrowband communications such as in maritime satellite communications. The effects of various fading reduction measures in the up and down links are considered.