Communications: directive radio wave systems and devices (e.g. – Radar transponder system – Unique identity
Patent
1993-01-25
1994-08-23
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Radar transponder system
Unique identity
342 50, 342 46, G01S 1380
Patent
active
053411404
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a transponder system for monitoring the locations of objects over relatively large distances.
It is an object of the invention to provide such a system which can be made available at relatively low cost and which is arranged so that each transponder can, in response to the receipt of an interrogating signal, transmit to a monitoring station a response peculiar to that transponder, or a group of transponders, and which response can be easily altered to take account of changing circumstances.
BRIEF SUMMARY OF THE INVENTION
It is envisaged that a particularly advantageous application of invention might be to the monitoring of licenced fishing vessels, or to the monitoring of arms equipment, e.g. missiles and tanks.
WO/89/05460, for example, discloses a transponder system comprising an interrogating source of H.F. electromagnetic radiation and a plurality of transponders. The present invention is characterized in that each transponder includes a token reader unit to receive a removable token including on board data processing capability, the transponders, or a group of transponders, each being arranged when interrogated to transmit a unique H.F. response modulated by information carried upon the token.
Because of the H.F. signals used, typically between 4 and 28 MHz, the system is operative over large distances, say up to 3500 Km. Because of the token reader unit and the nature of the token, the transponders themselves can be made at relatively low cost and the information carried upon the token can be easily changed.
In the case of the fishing vessel application mentioned above, each vessel licenced under the scheme would be required to have a transponder. A token, e.g. a smart card, would be bought as a licence by the vessels operator and, in addition to the information identifying the particular vessel, could also have other information such as whether the token has expired encoded onto the token and that information additionally could be used to modulate the response.
The token may be replaced when updating is required, but preferably the token reader unit includes token writing means and the interrogating source is operative to transmit information to be written onto the token. In this way updating can be accomplished remotely.
One disadvantage of an H.F. radar system is its poor positional resolution, which means that it can be difficult to locate an identified object with any greater accuracy than about 10 Km or so.
Preferably each transponder is operatively connected to navigational satellite receiving means and is arranged when interrogated to transmit information indicative of the position of the transponder.
In this way, the monitoring station can be provided with information on the precise location of a vehicle so equipped even if its location cannot be accurately found using a reflected radar signal.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be well understood, embodiments thereof will now be described with reference to the diagrammatic drawings, in which:
FIG. 1 shows a diagrammatic representation of a transponder system;
FIG. 2 shows a schemmatic view of a transponder unit for use in the system FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
It will be appreciated that the transponder systems of the present invention are broadly applicable to cases where it is designed to continuously monitor and communicate automatically with one or more of a large number of mobile locations.
As previously discussed, one particular application for the invention is for a fishing vessel monitoring system. Fishing vessels often operate in large numbers over a very large area of sea, making monitoring difficult. In certain cases, where licencing schemes are operating, it is often difficult to locate or enforce licences, but the present invention is intended to overcome this problem.
In FIG. 1 an interrogating and, optionally, monitoring station IS may be ship or shore mounted and arranged to transmit an H.F. radar interrogating sig
GEC--Marconi Limited
Sotomayor John B.
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