The beginning of new millenium sees an important milestone in military aviation communication with the introduction of the first Super-High-Frequency (SHF) airborne satellite communication (Satcom) terminals, which are due to enter service on Nimrod maritime reconnaissance aircraft (MRA4). Satcom terminals using the Ultra-High-Frequency (UHF) band have been fitted to larger aircrafts for a number of years. Although relatively simple to install and comparatively inexpensive, UHF satcoms(240-270 & 290-320 MHz bands) suffers from very limited capacity (a few 25 KHz channels per satellite) and are prone to multipath & unintensional interference due to their poor antenna selectivity. SHF satcoms (7.25 ? 7.75 & 7.9-8.4 GHz) offer significantly increased bandwidths (hundreds of MHz) for high data rates or increased use of spread-spectrum techniques, together with localised coverage and adaptive antenna techniques for nulling unwanted signals or interference.
For airborne platforms, the advantages of SHF satcoms come at the expense of a significant additional burden in terms of antenna siting and pointing, particularly for smaller, highly agile aircrafts. Antenna should be large enough to support the desired data rate and to provide enough directivity to minimise interference with adjascent satellites and avoid detection by hostile forces. Another feature of satcoms, unique to aircraft, is the effect of unwanted modulation from moving parts such as helicopter rotor blades, propellers and jet engines.
This paper gives an overview of development of airborne SHF and also Extremely-High-Frequency (EHF) satcom techniques, and terminal demonstrators by DERA (Defence Evaluation and Research Agency). This research is aimed at providing affordable, secure and robust satcoms to a range of military aircraft, supporting ground attack and reconnaissance roles to surveillance, transport and tanker aircraft.
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Future satellite communication
ABSTRACT
This paper outlines some of the techniques being developed to provide affordable, reliable satellite communications suitable for a wide range of military aircraft, from agile platforms such as jets and helicopters to surveillance, tanker and transport aircraft. It also gives an overview of airborne SHF (Super High Frequency) and also EHF (Extremely High Frequency) satcom techniques. Although presently used UHF (Ultra High Frequency) satellite communication are relatively simple to install and comparatively inexpensive, suffer from very limited capacity and are prone to multipath and unintentional interference due to their poor antenna selectivity. Whereas, the SHF satcoms offer significantly increased bandwidth for high data rates or increased use of spread-spectrum techniques, together with localized (spot) coverage and adaptive antenna techniques “ for nulling unwanted signals or interference.
INTRODUCTION
The beginning of new millennium sees an important milestone in military aviation communication with the introduction of the first Super-High-Frequency (SHF) airborne satellite communication (Satcom) terminals, which are due to enter service on Nimrod maritime reconnaissance aircraft (MRA4). Satcom terminals using the Ultra-High-Frequency (UHF) band have been fitted to larger aircrafts for a number of years. Although relatively simple to install and comparatively inexpensive, UHF satcoms(240-270 & 290-320 MHz bands) suffers from very limited capacity (a few 25 KHz channels per satellite) and are prone to multipath & unintentional interference due to their poor antenna selectivity. SHF satcoms (7.25 “ 7.75 & 7.9-8.4 GHz) offer significantly increased bandwidths (hundreds of MHz) for high data rates or increased use of spread-spectrum techniques, together with localised coverage and adaptive antenna techniques for nulling unwanted signals or interference.
For airborne platforms, the advantages of SHF satcoms come at the expense of a significant additional burden in terms of antenna siting and pointing, particularly for smaller, highly agile aircrafts. Antenna should be large enough to support the desired data rate and to provide enough directivity to minimize interference with adjacent satellites and avoid detection by hostile forces. Another feature of satcoms, unique to aircraft, is the effect of unwanted modulation from moving parts such as helicopter rotor blades, propellers and jet engines.
This paper gives an overview of development of airborne SHF and also Extremely-High-Frequency (EHF) satcom techniques, and terminal demonstrators by DERA (Defence Evaluation and Research Agency). This research is aimed at providing affordable, secure and robust satcoms to a range of military aircraft, supporting ground attack and reconnaissance roles to surveillance, transport and tanker aircraft.
MILITARY PERSPECTIVE
The UK Ministry of Defence (MoD) currently operates a constellation of three geostationary military communication satellites collectively known as skynet. The current generation of skynet 4 satellites provides satellite communication for all types of armed services at both UHF and SHF bands. Demand for all types of military satcom is rising rapidly, due principally to the need for even more timely information to prosecute operations effectively. Another factor is the growing expectations of service personnel familiar with a world of instant global communication and rapid availability of information via internet-type services.
Satcoms can span distance, terrain and hostile forces to provide a global reach for dispersed mobile platforms such as aircraft, submarines, surface ships, vehicles and man-packs. Fig.1 illustrates schematically, the breadth of military aerial roles that satcom may be required to support in future, providing global beyond-line-sight communications between aircraft and commander in theatre. Information carried by satellite could include:
¢ Near-real-time command & control “ tasking, position, reporting etc.
¢ Data from reconnaissance & surveillance aircraft.
¢ Targeting data for stand-off weapons.
¢ Situation awareness.
¢ Transfer data from dissimilar and/or geographically separated line-of-sight (LOS) networks.