GB2247379A

GB2247379A - Repeater buoy

Info

Publication number: GB2247379A
Application number: GB9018607A
Authority: GB
Inventors: David John Berry
Original assignee: STC PLC
Current assignee: STC PLC
Priority date: 1990-08-24
Filing date: 1990-08-24
Publication date: 1992-02-26
Anticipated expiration: 2010-08-24
Also published as: GB2247379B; GB9018607D0

Abstract

A free-floating, radio repeater buoy A for enhancing operation of a submarine master communication system by extending the communication range and/or changing the frequency or channel of communication. Conveniently the buoy is launched from the submarine prior to establishing a communication link via a towed transceiver B. Security is provided by frequency-hopping and broad-spectrum techniques. <IMAGE>

Description

REPEATER BUOY This invention relates to a communication link for use by submarines.

Submerged Submarines, when submerged, communicate with the outside world via a number of systems, one of which is a towed Buoyant Wire Antenna (BWA). In the near future other systems will be provided which will enable more deeply dived, faster submarines to communicate. Both of these examples are limited in the frequency bands in which they can operate due to size constraints. Physical size constraints also limit broadcast power. Furthermore these systems may not have the ability to receive satellite navigational data.

It is an object of the present invention to enhance the ability of the submarine to communicate when using a communications link such as those described in the examples above, and to allow the interrogation and capture of navigational data from satellite systems.

According to the present invention there is provided a submarine external communications system which uses a free-floating surface radio repeater buoy launched from the host submarine or from a supporting ship, aircraft, or separate submarine, to enhance the capabilities of the normally used submerged communications and navigation facilities of the submarine In one embodiment the equipment in the repeater buoy up- or down-converts the signal frequency to the frequency selected for onward transmission then re-transmits the signal on the selected frequency; the power of the transmission from the repeater buoy can be greater than the submarine systems radiated power. The repeater buoy may be dropped from a support ship or aircraft, or launched from the submarine.

In a similar way satellite navigation systems may be interrogated from the repeater buoy after receipt of instructions from the submarine via its communications system; the positional data then received by the buoy from the satellite would be transmitted to the submarine via the submarine communications system.

In order that the invention can be clearly understood reference will now be made to the accompanying drawings in which: Fig 1 shows an embodiment of the invention with the BWA.

Fig 2 shows another embodiment of the invention used with the future installation of Tethered Optical Fibre Buoy (TOF Buoy). Both figures use the same identifying letters for similar parts of the system.

Fig 3 shows a block diagram of one form of the repeater buoy suitable for use in either Fig 1 or Fig 2 systems.

The two embodiments to be discussed differ only in the frequencies that they normally use for communication, the towed antenna operating in the HF band while the future TOF buoy will probably operate in the UHF band. These two different systems may be catered for in the present invention either by incorporating equipment to handle both frequency bands, or by the provision of a separate module to be incorporated into the repeater buoy before launch, or by having separate repeater buoys for each master system. Essentially, however, the invention is not affected by the choice of master system or master to repeater radio link frequency. Furthermore, as mentioned above, a special frequency may be selected for the master to repeater link.The description which follows is common to both embodiments, and indeed to any other embodiments which other master systems not foreseen at this time may generate.

Referring to Figs 1 and 2 of the drawings, the subject of this invention is the repeater buoy A. In this embodiment it has been launched from a host submarine C by a suitable launcher such as a standard Submerged Signal Ejector tube with which all present submarines are fitted. The buoy ascends freely to the surface and is not linked to the submarine in any way.

The master communication system B may already be deployed, or may be deployed soon after the repeater buoy has reached the surface. Once the master system is deployed the submarine may communicate using any of the facilities available on the repeater buoy A. This is achieved by the master system transmitting to the repeater on a pre-arranged frequency selected for that type of system (in the figures: link path L1). This link will be made secure by any of the means currently available such as 'frequency hopping' or 'spread spectrum' techniques. The buoy will receive the signal and record all or part depending on message length, buoy memory size, and chosen link protocol, convert the signal to the required frequency and protocol for onward transmission, and transmit the signal on that frequency (link L4 in the figures).Simultaneous reception and transmission may be possible in certain circumstances.

Communication in the other direction is simply a reverse of this process. The repeater buoy A will receive signals at its selected operating frequencies, convert and reform them, and transmit them to the master system (link paths L3 and L2)/ Thus, for example a BWA master buoy B may communicate with the repeater buoy A by a low power HF band signal which the slave converts and boosts for onward transmission on a UHF satellite frequency.

Subsequently a weak HF signal might be detected by the repeater buoy, which has an antenna capable of better sensitivity and gain than that of the master system, which can be boosted and re-transmitted for reception by the master. In this mode the repeater buoy A acts as a simple re-generative repeater.

A further example for illustration is the future TOF buoy system, which because of size constraints can only contain limited services (perhaps only one channel) and limited power capability. In this example the master system would communicate with the repeater buoy which would then amplify and re-transmit the communication on any selected channel it is capable of.

In a final example the slave buoy A would be fitted with a Global Positioning System (GPS) module which would enable its position to be accurately fixed.

This position would be transmitted to the submarine either as raw data or after processing.

In a tactical situation where a number of TOF buoys are expended, a single repeater buoy might be used depending on the range of the radio equipment providing the link from the master to the slave and back. This aspect of repeater buoy use should result in system cost savings by allowing the deliberate selection of TOF buoys with limited communication services even in cases where the TOF buoys are not size constrained.

In the embodiment described, security would be provided in a number of ways: The radio link between the slave and master would be deliberately range limited and would use 'frequency hopping' or 'spread spectrum' techniques wherever possible. Data such as software keys and the message itself would be stored in the repeater buoy only for the short time necessary for transmission to to be completed. Physical security might suggest that the buoy memories can be further purged or the buoy destroyed should any attempt be made to remove it from the water. The buoy would be scuttled after used either after a pre-set time delay or on receipt of a coded signal from e.g. a host submarine. Alternatively, it my be configured to scuttle on consistent loss of the master to buoy link L1.

Referring now to Fig 3 there is shown one example of a repeater buoy A. The buoy comprises an aerial 1 used in common for reception and transmission.

A transmit/receive changeover switch 2 couples the aerial to the transmit or receive circuitry, as desired. A central control 3 provides control of the various functions, and the switch 2 remains in the position shown for the buoy to listen for incoming instructions in its idle state. It is configured to receive messages in a chosen band. The received message is amplified 4 band pass filtered 5, amplified 6 and decoded 7. The decoder 7 provides control word instruction 7A to the central control 3 from the received signal. The received signal is demodulated, 8, and stored temporarily in a store 9. Control centre 3 then determines where to re-transmit the received signals on the same or another band, and modulator 10 will modulate a chosen carrier frequency (oscillator) with the signals and re-transmit them, the modulated carrier being adjustably amplified (12) and amplified (13) and coupled to axial 1 via switch 2 which will be changed over to the transmit position by central control 3.

Central control 3 controls, by the various connections shown, the receive band (5A) and the transmit band (11A).

The block circuit diagram of the buoy A is only one example and suitable for UGF Satcomm and HF frequencies.

The shape of the buoy would be substantially cylindrical and of elongate form, and preferably carried by a submarine in addition to the submarine's own master communications system.

Claims

CLAIMS:

1. A submarine external communications system which uses a free-floating surface buoy launched from a host submarine or from a supporting ship, aircraft, or separate submarine, to enhance the capabilities of the normally used submerged communications and navigation facilities of the submarine.

2. A submarine antenna communications system comprising a tethered transceiver buoy via which communications to and/or from the submarine passes, and a free-floating transceiver buoy arranged to receive signals from and/or transmit signals to the tethered buoy so as to change the effective distance over which the submarine can communicate information or the frequency or channel on which the information is carried.

3. A free-floating radio repeater buoy comprising means for re-transmitting received radio signals for a submarine communicating through a tethered radio buoy, whereby to change the distance over which the submarine can communicate and/or the frequency or channel over which information is carried to and/or from the submarine.

4. A buoy as claimed in claim 3 which can receive signals on one frequency and transmit them on another.

5. A buoy as claimed in claim 3 or 4, which can communicate with existing satellite navigation systems such as GPS and transmit positional data to the submarine.

6. A buoy as claimed in any of claims 3 to 5 which can receive signals and re-transmit them at a greater radiated power than the original source.

7. A buoy as claimed in any of claims 3 to 6 which by reason of greater sensitivity than the normally used submarine systems can receive signals from the outside world which would normally be undetected, and re-transmit them to the host submarine.

8. A buoy as claimed in claim 4, comprising means to select a received radio signal, means to decode the signal, and means to store the signal before re-transmission.

9. A repeater buoy substantially as hereinbefore described with reference to the accompanying drawings.

10. A submarine equipped with a system as claimed in claim 1 or claim 2.