AU707672B2

AU707672B2 - High speed data link

Info

Publication number: AU707672B2
Application number: AU23745/97A
Authority: AU
Inventors: Stephen Baker; John James Douglass; Con Nakos; Angelo Romano Sarti
Original assignee: Commonwealth of Australia
Current assignee: Commonwealth of Australia
Priority date: 1996-04-30
Filing date: 1997-04-30
Publication date: 1999-07-15
Anticipated expiration: 2017-04-30
Also published as: AU2374597A

Description

WO 97/41450 PCT/AU97/00255 1 TITLE: HIGH SPEED DATA LINK This invention is for a method and apparatus for the transfer of information or data between two locations wherein the information is to be transferred by remote means.

In particular this invention is for a method and apparatus for the transfer of information between at least two locations when at least one of the locations is subject to positional change, such as a moving vehicle.

BACKGROUND OF THE INVENTION The transfer of information, data or signals from a moving vehicle or target, 1 0 moving either at a constant or variable velocity, requires that the information or data be transferred by electromagnetic radiation. To do this effectively at high rates of data transfer requires high effective radiated power (ERP). One effective way to provide this high ERP is by the use of high gain antennas in the high radio frequency range, and in particular in the microwave frequency range, although UHF and VHF could also be used. These antennas, such as dishes, have very narrow beamwidths and therefore must be accurately pointed at the vehicle. If the vehicle or target is moving, or periodically changes its position, the antenna must be re-aligned to track the vehicle or target for the high data rates to continue.

Various types of tracking are currently employed including Monopulse or split beam antennas, conically scanned antennas or beam switching techniques to derive positional data. Closed loop control systems are then used to steer the antenna. However, this system requires external input to set the system within its capture range and the precision and speed of the system are dictated by the requirements of the tracking system loop not by the main requirement, i.e.

the antenna beamwidth and relative target position. Furthermore these systems are complex and expensive to realise and are only required for non cooperative targets.

It is an object of this invention to overcome some of the above problems or to at least provide the public with a useful alternative.

WO 97/41450 PCT/AU97/00255 2 DISCLOSURE OF THE INVENTION This invention eliminates the requirement for expensive closed loop tracking systems for the antenna by relying on navigational aids on board a vehicle or target. In particular, by utilizing positional information derived from navigational aids, such as the global positioning satellite signals (GPS) the vehicle transmits its position via a low speed radio data link. This can be achieved by using relatively low ERP and is therefore suitable for omnidirectional antennas. The received positional information is then used to control a main high-gain microwave antenna by correctly pointing it towards 1 0 the vehicle or target.

This system provides the additional advantages that it: Eliminates complex radio frequency signal processing to derive positional information about the vehicle; Eliminates tracking errors and losses due to multipath signal effects on the received signal; Eliminates data corruption and loss due to tracking errors and jitter; Allows longer effective time for data transfer due to more effective tracking; Is simpler, lighter and lower in cost then previous systems.

Therefore in one form of the invention though this need not be the only or indeed the broadest form there is proposed a method of tracking a target by; calculating the position of said target with a first positioning means located on said target by use of navigational aids; transmitting the calculated position of said target by a transmitting means located on said target by use of a low speed radio data link; and receiving the transmitted position of the target on a receiver means and calculating the position of said target relative to an antenna by use of a calculating means and further calculating the pointing angles of said antenna necessary to effect tracking of said target.

In a further form of the invention there is proposed a method of tracking a target so as to enable data transfer from the target at a first location to an antenna at a second location by; calculating the position of said target with a first positioning means located on said target by use of navigational aids; WO 97/41450 PCT/AU97/00255 3 transmitting the calculated position of said target by a transmitting means located on said target by use of a low speed radio data link; and receiving the transmitted position of the target on a receiver means and calculating the position of said target relative to an antenna by use of a calculating means and further calculating the pointing angles of said antenna necessary to effect tracking of said target to enable data transfer from said target to said antenna to be transferred at a high data rate in the microwave frequency range.

In a yet further form of the invention there is proposed a target tracking 1 0 apparatus to enable data transfer from the target at a first location to an antenna at a second location by; a first positioning means located on said target being adapted to calculate its position by use of navigational aids; a transmitting means on said target adapted to transmit the calculated 1 5 position of the target calculated by the first positioning means by use of a low speed radio data link; a receiver means adapted to receive the transmitted position of the target and effect a received positional output; a calculating means adapted to input said positional output so as to calculate the relative position between said target and an antenna and further adapted to calculate the pointing angles of said antenna necessary to effect tracking of said target so that data transfer from said target to said antenna is transferred at a high data rate.

In preference the navigational aids makes use of global positioning satellite signals (GPS).

In preference the target is an aircraft, while the antenna is a high gain antenna located on the ground and data is transferred from said aircraft to the high gain antenna in the microwave frequency range. However, the antenna could very well be positioned on another platform, such as a vehicle or a satellite.

3 0 In preference the low speed radio data link is effected by use of an omnidirectional antenna with low effective radiated power positioned on said target.

In preference the receiver means is located closely to the high gain antenna WO 97/41450 PCT/AU97/00255 4 whose position is known. However, the receiver means could be co-located with the high gain antenna eliminating the need for further control data transmissions between the target and the high gain antenna.

In a yet further form of the invention there is proposed a target tracking apparatus to enable data transfer from the target at a first location to an antenna at a second location by; a first positioning means located on said target being adapted to calculate its position by use of navigational aids; a transmitter means located on said target adapted to transmit the 1 0 calculated position of the target calculated by the first positioning means by use of a low speed radio data link; a second positioning means located on said antenna being adapted to calculate its position by use of navigational aids; a receiver means located at said antenna adapted to receive the 1 5 transmitted position of the target from the first positioning means and the position of the antenna from the second positioning means and effect a received output; a calculating means adapted to input said received output so as to calculate the relative position between said target and antenna and further adapted to calculate the pointing angles of said antenna necessary to effect tracking of said target so as to enable data transfer from said target to said antenna to be transferred at a high data rate.

In a yet further form of the invention there is proposed a target tracking apparatus to enable data transfer from the target at a first location to an antenna at a second location by; a first positioning means located on said target being adapted to calculate its position by use of navigational aids; a first transmitting means located on said target adapted to transmit the position of the target calculated by the first positioning means by use of a low 3 0 speed radio data link; a second positioning means located on said antenna being adapted to calculate its position by use of navigational aids; a second transmitting means located on said antenna adapted to transmit the position of the antenna calculated by the second positioning means by use of a low speed radio data link; a receiver means adapted to receive the transmitted position of the WO 97/41450 PCT/AU97/00255 target from the first positioning means and the position of the antenna from the second transmitting means and effect a received output; a calculating means adapted to input said received output so as to calculate the relative position between said target and antenna and further adapted to calculate the pointing angles of said antenna necessary to effect tracking of said target so as to enable data transfer from said target to said antenna to be transferred at a high data rate.

BRIEF DESCRIPTION OF THE DRAWINGS To further aid in the description of the invention reference is now made to the figures in which Fig 1 is a schematic diagram showing one preferred embodiment of the invention for the transfer of data between an aircraft and a stationary dish antenna; Fig 2 is a schematic diagram showing another embodiment of the invention for the transfer of data between a variable ground position and an aircraft; Fig 3 is a block diagram showing another embodiment of the invention for the transfer of data between two aircraft; Fig 4 is a block diagram showing another preferred embodiment of the invention for the transfer of data between two ground positions by the use of an aircraft.

DESCRIPTION OF THE PREFERRED

EMBODIMENT

Turning now to the drawings in detail there is shown in Fig 1 an aircraft which is adapted to calculate its position by the use of signals 11 from the Global Positioning Satellites (GPS) navigational aid network. That positional information is then relayed from the aircraft 10 via an omni-directional low speed datalink 12 to a receiver 13. Suitable processors 14 then calculate the direction of the aircraft 10 relative to an antenna 15 and use that information for track control data 16 which is used to point the antenna 15 in the direction 17 of aircraft WO 97/41450 PCT/AU97/00255 6 Once the antenna 15 is pointing in the direction 17 of the aircraft 10 large data rates 20 can be achieved between aircraft 10 and antenna 15 in the microwave frequency range. Once data has been transferred, say from the aircraft 10 to the antenna 15 then it is fed to a central communications computer 25. Of course data could just as well be uploaded from the antenna to the aircraft once the antenna is pointing in the direction of the aircraft.

The applicability of such a system is quite large. It could for example be used for advanced telecommunications that require high data rates between an aircraft and a ground antenna. Alternatively, an aircraft could be used to scan 1 0 an area for enemy forces or even for mineral deposits and enable the collected and transferred data to be relayed directly to a central control room (not shown) and/or to a data recording means. The information being substantially instantaneous is a great improvement on current techniques which include the data being stored on magnetic media within an aircraft and 1 5 only accessible when the aircraft has landed and the data physically removed form the aircraft in its stored form. It thus allows decisions to be made based on current information. Thus if looking for mineral deposits, the aircraft could be directed to look at one area in particular with different imaging instrumentation or resolution.

If used for scouting enemy forces it must be remembered that an aircraft can scan up to several hundred kilometres away. The ability to relay that information another several hundred kilometres (limited by the Earths curvature) means that one can obtain vast quantities of information about a location up to 500 km away. This is a great strategical advantage.

In experimental trials it has been found that such a system reliably transfers data at rates of some 8 Mbytes per second.

In addition the processors 14 may include modelling algorithms which predict the position of the aircraft 10 based upon its speed, direction and previous position. Thus if information about the aircraft speed and direction is also 3 0 transmitted via the low speed datalink 12, the modelling means that data updates via the low speed datalink 12 need only occur every several seconds.

Because the antenna pointing error rates can be of the order of several degrees, an antenna tracking an aircraft that is some several hundred kilometres away allows the aircraft to be within a 2 kilometre cell. Even if the WO 97/41450 PCT/AU97/00255 7 aircraft is travelling at some 2000 km per hour, it only moves about 1100 meters in two seconds which is well within the 2 km error range. However, since data is usually updated much more frequently than every 2 seconds, it is virtually impossible to loose track of an aircraft by using this invention. The only time where there may be a problem with tracking an aircraft is where it flies directly overhead of an antenna. In such a scenario the antenna positioning motors would simply not be able to angularly move the antenna to keep up with the aircraft. Even so, in such an example the model could then predict the probable position of the aircraft (if its motion was constant) and 1 0 point the antenna to that direction.

Turning now to Figure 2 there is shown another embodiment of the invention when data 20 is to be transferred from both a moving aircraft 10 and an antenna 15 located on a vehicle 18. Both the aircraft 10 and the antenna then utilise signals 11 from the GPS system and relay information on their 1 5 position, speed and direction to the processors 14 via receiver 13. This information is relayed from the aircraft via the low speed data link 12 whilst it can simply be cabled to processors 14 (not shown) from antenna 15 if the receiver is co-located on the vehicle 18 with antenna 15. The processors then simply take into account not only the position of the aircraft 10 but also the position of antenna 15. This would not only overcome problems if the antenna was on a moving vehicle, it also solves the problem of having to update the processors if the antenna is of a quasi-permanent type and allows the system to be more robust.

Figure 3 shows another use of the invention if it is used for air-to-air data transfer. Obviously since these are high gain antennas they are necessarily large and may not be suitable for small aircraft. However, if there is a large transporter plane, for example 21, that is capable of housing a large dish antenna 22 say of some 10 feet in diameter, then this invention could very well be-used for large data transfer between two aircraft. It could even be used for 3 0 close ground inspections between a mother craft and a drone.

Similarly Figure 4 shows another use of the invention for transferring data at high rates between two ground stations by using an aircraft 10 as a transfer medium. This invention enables the use of an aircraft by enabling the aircraft to relay positional information to both antennae via a low speed datalink 12 which then tracks the aircraft.

WO 97/41450 PCT/AU97/00255 8 Throughout this specification various indications have been given as to the scope of this invention but the invention is not limited to any one of these but may reside in two or more of these combined together. The examples are given for illustration only and not for limitation.

Throughout this specification and the claims that follow unless the context requires otherwise, the words 'comprise' and 'include' and variations such as 'comprising' and 'including' will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

1. A method of tracking a target by; calculating the position of said target with a first positioning means located on said target by use of navigational aids; transmitting the calculated position of said target by a transmitting means located on said target by use of a low speed radio data link; and receiving the transmitted position of the target on a receiver means and calculating the position of said target relative to an antenna by use of a calculating means and further calculating the pointing angles of said antenna 1 0 necessary to effect tracking of said target.

2. A method of tracking a target so as to enable data transfer from the target at a first location to an antenna at a second location by; calculating the position of said target with a first positioning means located on said target by use of navigational aids; 1 5 transmitting the calculated position of said target by a transmitting means located on said target by use of a low speed radio data link; and receiving the transmitted position of the target on a receiver means and calculating the position of said target relative to an antenna by use of a calculating means and further calculating the pointing angles of said antenna necessary to effect tracking of said target to enable data transfer from said target to said antenna to be transferred at a high data rate in the microwave frequency range.

3. A method of tracking a target as in claim 1 or 2 wherein the navigational aids makes use of global positioning satellite signals (GPS).

4. A method of tracking a target as in any one of the above claims wherein the target is an aircraft, and the antenna is a high gain antenna located on the ground and data is transferred from said aircraft to the high gain antenna in the microwave frequency range.

A method of tracking a target as in any one of claims 1 to 3 wherein the 3 0 antenna is a high gain antenna located on a satellite.

6. A method of tracking a target as in any one of the above claims wherein the low speed radio data link is effected by use of an omnidirectional antenna with WO 97/41450 PCT/AU97/00255 low effective radiated power positioned on said target.

7. A method of tracking a target as in any one of the above claims wherein the receiver means is located closely to the high gain antenna whose position is known.

8. A method of tracking a target as in any one of claims 1 to 6 wherein the receiver means is co-located with the high gain antenna.

9. A target tracking apparatus to enable data transfer from the target at a first location to an antenna at a second location by; a first positioning means located on said target being adapted to 1 0 calculate its position by use of navigational aids; a transmitting means on said target adapted to transmit the calculated position of the target calculated by the first positioning means by use of a low speed radio data link; a receiver means adapted to receive the transmitted position of the 1 5 target and effect a received positional output; a calculating means adapted to input said positional output so as to calculate the relative position between said target and an antenna and further adapted to calculate the pointing angles of said antenna necessary to effect tracking of said target so that data transfer from said target to said antenna is transferred at a high data rate.

A target tracking apparatus to enable data transfer from the target at a first location to an antenna at a second location by; a first positioning means located on said target being adapted to calculate its position by use of navigational aids; a transmitter means located on said target adapted to transmit the calculated position of the target calculated by the first positioning means by use of a low speed radio data link; a second positioning means located on said antenna being adapted to calculate its position by use of navigational aids; 3 0 a receiver means located at said antenna adapted to receive the transmitted position of the target from the first positioning means and the position of the antenna from the second positioning means and effect a received output; a calculating means adapted to input said received output so as to WO 97/41450 PCT/AU97/00255 11 calculate the relative position between said target and antenna and further adapted to calculate the pointing angles of said antenna necessary to effect tracking of said target so as to enable data transfer from said target to said antenna to be transferred at a high data rate.

11. A target tracking apparatus to enable data transfer from the target at a first location to an antenna at a second location by; a first positioning means located on said target being adapted to calculate its position by use of navigational aids; a first transmitting means located on said target adapted to transmit the position of the target calculated by the first positioning means by use of a low speed radio data link; a second positioning means located on said antenna being adapted to calculate its position by use of navigational aids; a second transmitting means located on said antenna adapted to 1 5 transmit the position of the antenna calculated by the second positioning means by use of a low speed radio data link; a receiver means adapted to receive the transmitted position of the target from the first positioning means and the position of the antenna from the second transmitting means and effect a received output; a calculating means adapted to input said received output so as to calculate the relative position between said target and antenna and further adapted to calculate the pointing angles of said antenna necessary to effect tracking of said target so as to enable data transfer from said target to said antenna to be transferred at a high data rate.

12. A target tracking apparatus as in any one of claim 9 to 11 wherein the navigational aids makes use of global positioning satellite signals (GPS).

13. A target tracking apparatus as in any one of claims 9 to 12 wherein the target is an aircraft, and the antenna is a high gain antenna located on the ground and data is transferred from said aircraft to the high gain antenna in the microwave frequency range.

14. A target tracking apparatus as in any one of claims 9 to 12 wherein the antenna is a high gain antenna located on a satellite.

A target tracking apparatus as in any one of claims 9 to 14 wherein the low WO 97/41450 PCT/AU97/00255 12 speed radio data link is effected by use of an omnidirectional antenna with low effective radiated power positioned on said target.

16. A target tracking apparatus as in any one of claims 9 to 15 wherein the receiver means is located closely to the high gain antenna whose position is known.

17. A target tracking apparatus as in any one of claims 9 to 15 wherein the receiver means is co-located with the high gain antenna.

18. A method of tracking a target as described herein and with reference to the accompanying drawings.

19. A target tracking apparatus as described herein and with reference to the accompanying drawings.