Communications: directive radio wave systems and devices (e.g. – Return signal controls radar system – Antenna control
Reexamination Certificate
1998-12-22
2001-10-02
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls radar system
Antenna control
C342S073000, C342S074000, C342S080000, C342S149000, C342S175000, C342S195000, C342S368000
Reexamination Certificate
active
06297763
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of optimizing the coverage area of a sensor, preferably a radar system, which is arranged on a mobile platform.
BACKGROUND
In the use of sensors, for example radar, it may be desirable to use a sensor to cover a greater area than the range of the sensor allows. A common way of achieving such increased coverage is to arrange the sensor on a mobile platform, the platform then being moved in such a manner that the desired area is covered. Aircraft, ships and cars may be cited as examples of platforms for sensors.
In the case of the above mentioned type of movement with a sensor platform, a problem arises regarding how the platform is to be moved in order to achieve the desired coverage. This problem may arise in particular if the range of the sensor is not symmetrical. If the sensor is a radar system, this problem may arise above all in connection with so-called group antennas, in other words antennas with an antenna pattern or pointing direction that is controlled electrically, since such antennas often have a range which is angle-dependent at least in one plane. The range of the sensor may, however, be symmetrical in the plane in which the range is angle-dependent.
U.S. Pat. No. 4,129,866 discloses a method of solving a similar problem for a radar system with its antenna arranged on top of an aircraft. In the solution that is described, the carrier aircraft is flown along a sinusoidal path in relation to the ground plane. This may be said to create disadvantages since the pointing direction of the antenna in the vertical direction will vary in an undesirable manner in connection with the turns of the aircraft.
Other known solutions are described in, inter alia, U.S. Pat. No. 5,097,267, U.S. Pat. No. 4,779,097 and U.S. Pat. No. 5,357,259. These specifications disclose methods of solving coverage problems in connection with group antennas mounted on aircraft. All the solutions described in these specifications comprise mechanical steering of the antennas in relation to the platform, which may be said to lead to complex and thus expensive solutions.
SUMMARY
The problem that is solved according to the invention is thus that of optimizing within a given area the coverage achieved by a sensor, preferably a radar, which area may itself contain a number of smaller part areas. In particular, the invention aims to solve the problem that arises if the area in question is greater than the coverage area of the sensor, and the sensor has a symmetrical but angle-dependent range in at least one plane and is arranged on a mobile platform, the main movement of which takes place in the plane in which the range of the sensor is symmetrical.
This problem is solved with the aid of an optimization method which comprises determining at least two movement directions for the sensor platform, determining a centre of movement for these two movement directions, and also determining the periods of time for which the sensor platform is to move in each of said two movement directions.
In a preferred embodiment, the optimization comprises minimizing the sum of the differences between the desired and the achieved range in azimuth (angle).
A fact that is made use of in the application of the invention is that the movement of the sensor platform in the great majority of cases is considerably smaller than the range of the sensor, which means that the sensor platform can, notwithstanding its movement, essentially be considered to be stationary.
In a preferred embodiment, the two movement directions form a closed contour, in which case their centre of movement constitutes the centre point of the contour. In another embodiment, in which the two movement directions do not form a closed contour but rather a continuous but not closed shape, the centre of movement forms a center line in this continuous shape.
In both the above cases, the centre of movement of the platform is preferably located within the search area.
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Bentland Benny
Thomson Ola
Burns Doane Swecker & Mathis L.L.P.
Gregory Bernarr E.
Telefonaktiebolaget LM Ericsson (publ)
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