Abstract
As a follow-on to the 2002 digital television (DTV) broadcast demonstration from a solar-powered stratospheric flying wing, a prototype stratospheric airship was used for a more realistic DTV broadcast demonstration in 2004, albeit at a lower altitude. The DTV signal was occasionally lost at the receiver directly below the airship during the demonstration. Adverse antenna-vehicle integration effects were investigated using a commercially available antenna simulation software, because the radiation pattern of the antenna on the airship could not be measured directly. The ground handling bars on the airship gondola were found to introduce deep and sharp nulls into the radiation pattern of the broadcast antenna. Some mitigation techniques that would have fitted within the constraints of the time are discussed. Changing to nonconductive ground handling bars and a multiturn helical antenna would have avoided the problem, according to the simulation results.
Highlights
Aircraft flying in the stratosphere offers numerous advantages as communications platforms compared to present day terrestrial and satellite infrastructure [1,2,3,4]
The far field radiation pattern of the helical antenna model in FEKO was in reasonable agreement with the radiation pattern of the actual digital TV (DTV) broadcast antenna measured in an anechoic chamber on the gain compliance ground plane
The remainder of this paper presents simulation results for various means of mitigating null formation in the radiation pattern of the helical antenna installed on the gondola
Summary
Aircraft flying in the stratosphere offers numerous advantages as communications platforms compared to present day terrestrial and satellite infrastructure [1,2,3,4]. Freeflight or partially steered weather balloons, despite being low cost and readily available, are considered to only be applicable to scientific and low-data-rate missions due to lack of precise flight control [4, 6, 7]. Manned aircraft are another mature technology, having been developed over the last 55 years for military surveillance applications, but are limited to a maximum of about 6 hours on station due to pilot endurance. Several possible mitigation techniques and alternative antenna designs which would have fitted within the constraints of the 2004 demonstration were compared
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