Showing papers on "L band published in 1986"

Characteristics of L-band multipath fading due to sea surface reflection in aeronautical satellite communications

Abstract: For low G/T ship-based earth stations in future maritime satellite communications, the effect of multipath fading due to sea surface reflection will be very important at low elevation angles. However, a practical model of the L -band multipath fading for fade prediction has not been available so far. A practical fading model is presented based on the shadowed Kirchhoff approximation theory for the coherent and incoherent components of the scattered power as a function of sea surface conditions. Using this model, theoretical fading depths are presented as a function of elevation angle, wave height, and antenna gain. The results indicate that intense fading occurs for wave heights greater than 50 cm, and the dependence on wave height is small under these conditions at L -band frequencies. Theoretical results presented agree well with experimental results obtained by field experiments.

L-band antenna for mobile satellite broadcasting

Abstract: A slotted tube antenna is arranged vertically with respect to a highly conductive reflective plane to produce a conical, substantially circular-polarised polar diagram for a mobile L-band satellite radio; in this case, the cylindrical antenna tube, which is arranged vertically with respect to the reflective plane and has a specific length, is excited as a vertically polarised linear emitter, while at the same time, but separately therefrom, a longitudinal slot of predetermined length designed in the cylindrical antenna tube is excited as a horizontally polarised dipole at a specific height above the reflective plane. By suitable dimensioning of the antenna tube and of the slot designed therein, and by suitable arrangement of the antennal centre of gravity above the highly conductive reflective plane, an overall circular-polarised emitter is produced having an optimum radiation characteristic for mobile satellite radio, with a circular polar diagram in the azimuth plane and a beam in the elevation plane with maximum radiation of the main lobe at an elevation angle of approximately 30 DEG , which is satisfactory, for example, for the conditions in Europe.