Introduction

Multipath, especially sea surface-reflected multipath, is a significant parameter to be considered in the design of an aeronautical mobile-satellite system in the 1.5/1.6 GHz bands. The new information contained in section 3 of this Report reconfirms the results of previous experiments and extends the multipath characterization investigations undertaken.

A number of factors related to the potential impact of sea-reflected multipath on aeronautical mobile-satellite communications made the characterization of this parameter a principal subject for early experimental investigation, which began in the early 1970s. The factors included:

1) the anticipated power level of the reflected signal relative to the direct path signal;

2) the characteristics of the multipath signal; and

3) the relative inability of aircraft antennas to discriminate the sea reflected signal (especially for low elevation angles and for broad beamwidth, relatively inexpensive low gain antennas).

Section 4 of this Report contains some early information on the operational performance of one phased array aircraft antenna installation with respect to the impact of sea surface multipath effects.