Communications: directive radio wave systems and devices (e.g. – Radar for meteorological use
Reexamination Certificate
2002-10-28
2004-01-13
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Radar for meteorological use
C342S092000, C342S093000, C342S159000, C342S162000
Reexamination Certificate
active
06677886
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable.
FIELD OF THE INVENTION
The present invention relates generally to air traffic control radar systems and more specifically to a method of suppressing weather and other airborne clutter in radar results.
BACKGROUND OF THE INVENTION
It has traditionally been difficult to tune a radar system parameter for high sensitivity while still keeping the false alarm rate low. The source of false alarms could be from system noise, weather clutter, surface clutter or airborne clutter. Weather clutter is rain, snow or hail, and shows up in radar readings. False alarms due to weather clutter are problematic because they can appear in large number of tracks affecting most parts of the radar display. This may also be the time when the radar is mostly needed for air traffic control and navigation. The weather clutter distracts and confuses the air traffic controller and reduces the usefulness of the radar system.
Most radar systems utilize a Moving Target Indication (MTI) technique to eliminate airborne and ground clutter. This technique takes advantage of the fact that the Doppler velocity of airborne clutter is relatively low in comparison with the Doppler velocity of aircraft. The MTI technique uses this difference in Doppler velocity to distinguish between aircraft and airborne clutter. A drawback associated with the MTI technique is that the MTI technique is not sufficient to isolate slow helicopters from fast moving weather.
A radar reading may show one or more detection clusters which have been detected by the radar system. Each detection cluster represents an aircraft, ground clutter, airborne clutter or the like. Existing Airport Surveillance Radars (ASR) use only one of a detection cluster shape's dimensions, such as amplitude, to distinguish between aircraft and clutter. The determination method is usually a simple threshold comparison of the detection cluster shape's dimension to determine whether the detection cluster represents aircraft or weather clutter. Accordingly, known ASR systems have not been able to provide a high degree of sensitivity while still limiting the amount of false alarms.
In view of the foregoing it would be desirable to provide a method for determining the presence of airborne clutter and to distinguish the occurrence of non-aircraft airborne weather clutter from the detection of airborne vehicles while limiting the amount of false alarms.
SUMMARY OF THE INVENTION
With the foregoing background in mind, it is an object of the present invention to provide a method of determining the presence of an airborne clutter in a radar system. The method includes determining the presence of a detection cluster or detection clusters in a radar scan, and characterizing the detection cluster(s). Confidence factors are calculated from the characterization of a detection cluster and a determination is made from the confidence factor whether the detection cluster represents airborne clutter.
In accordance with another aspect of the present invention, a radar tracking system for determining the presence of airborne clutter is presented. The radar system includes a Doppler filter, a constant false-alarm rate (CFAR) circuit, a binary integrator, a plot extractor and a tracker. The plot extractor includes a detection cluster classifier which is utilized to whether detection clusters represent airborne clutter.
In accordance with another aspect of the present invention, a computer product is provided. The computer program product comprises a computer useable medium having computer readable program code embodied thereon with instructions for providing a method of determining the presence of a weather clutter in a radar detection system. The computer program product includes instructions for determining the presence of a detection cluster in a radar scan, and characterizing the detection cluster. The computer program product further includes instructions wherein confidence factors are determined from the characterization of a detection cluster and a determination is made from the confidence factors whether the detection cluster represents airborne clutter.
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Daly, Crowley & Mofford LLP
Raytheon Company
Sotomayor John B.
LandOfFree
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