A Digital Broadcasting Experiment Using an Autonomous Stationary-keeping Airship

Abstract

A broadcasting system using a stratospheric platform,which is an air vehicle capable of remaining stationary at an altitude of 20 km,has been studied.Advantages of such a system are that it has a wider line-of-site area than a terrestrial system and a shorter propagation distance than a satellite system.However,such air vehicles have not been realized yet.An experiment in which a broadcasting signal is transmitted from a stationary airship at an altitude of 4 km is presented.The service area was defined as an area where the angle of elevation to the airship exceeded 10 degrees.A helical antenna was developed to provide higher gain in the oblique direction to distribute power uniformly.Received power was measured and reception using off-the-shelf receivers was verified in two flight tests.Stable reception was confirmed at several receiving points in the service area despite instability immediately below the airship.