Inmarsat

About: Inmarsat is a based out in . It is known for research contribution in the topics: Communications satellite & Geostationary orbit. The organization has 166 authors who have published 144 publications receiving 1642 citations. The organization is also known as: Inmarsat plc & Inmarsat-5.

Folded dipole microstrip antenna

Abstract: A folded dipole microstrip antenna is disclosed herein. The microstrip antenna includes a dielectric substrate for defining a first mounting surface and a second mounting surface substantially parallel thereto. A folded dipole radiative element is mounted on the second mounting surface. The microstrip antenna further includes a microstrip feed line, mounted on the first surface, for exciting the radiative element in response to an excitation signal. In a preferred implementation of the microstrip antenna an excitation signal is applied to the microstrip feed line through a coaxial cable. In such a preferred implementation the folded dipole radiative element includes a continuous dipole arm arranged parallel to first and second dipole arm segments separated by an excitation gap. The feed element is mounted in alignment with the excitation gap and is electrically connected to the continuous dipole arm. The antenna may additionally include a ground plane reflector separated from the folded dipole radiative element by a dielectric spacer for projecting, in a predetermined direction, electromagnetic energy radiated by the folded dipole radiative element. The thickness of the dielectric spacer between the ground plane reflector and the folded dipole radiative element is selected such that the impedance presented by the antenna to the coaxial cable is approximately fifty ohms.

Evolution of aeronautical communications for personal and multimedia services

Abstract: The demand to make air travel more pleasant, secure, and productive for passengers is one of the winning factors for both airlines and the aircraft manufacturing industry for which aeronautical communications is one of the enablers. This article describes current trends in the area of aeronautical passenger communication toward personal and wireless in-cabin communications and multimedia data networks. Technological challenges are summarized as well as market potentials and regulatory issues.

IMT-2000: service provider's perspective

Abstract: This article provides an overview of the important issues for the development of the next generation of wireless access systems from the service provider's perspective. The specifications for this future global wireless access system (IMT-2000) are currently being developed within the International Telecommunication Union (ITU).

Telemedicine and developing countries.

Abstract: A committee was established by the International Telecommunication Union in 1994 to study telemedicine, with particular reference to developing countries. A questionnaire was used to gather data. Fifty-eight responses were received, two-thirds from developing countries. In most developing countries the user did not pay for the telemedicine service, at least not directly. There were few instances of a commercial telemedicine service, and in most countries the telemedicine service was subsidized by the government or another party. The telemedicine 'value chain' describes how equipment suppliers, telecommunications operators and health-care professionals deliver their products or services to the client, who is eventually the ultimate user. Quite different configurations are conceivable, and an analysis of what could be a sustainable, cost-effective value chain in developing countries is required. It is clear that the rapidly growing interest in telemedicine challenges the leaders of the medical establishment to rethink the ways they provide their services and to address the medical needs of areas where such services are absent or in short supply.

The New Multichannel Radiospectrograph ARTEMIS-IV/HECATE, of the University of Athens

Abstract: We present the new solar radiospectrograph of the University of Athens operating at the Thermopylae Station since 1996. Observations cover the frequency range from 110 to 688 MHz. The radiospectrograph has a 7-meter parabolic antenna and two receivers operating in parallel. One is a sweep frequency receiver and the other a multichannel acousto-optical receiver. The data acquisition system consists of a front-end VME based subsystem and a Sun Sparc-5 workstation connected through Ethernet. The two subsystems are operated using the VxWorks real-time package. The daily operation is fully automated: pointing of the antenna to the sun, starting and stopping the obser- vations at pre-set times, data acquisition, data compression by 'silence suppression', and archiving on DAT tapes. The instrument can be used either by itself to study the onset and evolution of solar radio bursts or in conjunction with other instruments including the Nancay Decametric Array and the WIND/WAVES RAD1 and RAD2 low frequency receivers to study associated interplanetary phenomena.