Communications: directive radio wave systems and devices (e.g. – Radar ew
Reexamination Certificate
1999-10-12
2001-04-24
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Radar ew
C342S016000, C342S090000, C342S162000, C342S195000
Reexamination Certificate
active
06222479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to radar and sonar and more particularly to finding both conventional and stealth-modified targets by these means.
Radar and sonar equipment and techniques are well developed and widely used both militarily and otherwise, and the literature on these subjects abounds. Skolnik, for example, lists over one thousand references in his
Introduction to Radar Systems,
and his
Radar Handbook
covers the subject in even more detail.
Military and non-military applications differ, however, because enemy targets are attacked when detected and so best survive when they are hard to find, and are modified to make them so, while non-military targets survive best when they are deleted before there is any risk of collision, and are modified accordingly. While the most refined techniques for making military targets stealthy and the techniques for finding them despite stealth presumably have not been made public, it is clear that, at least with respect to detection of stealthcraft with prior art radars or sonars, this task becomes more difficult when these targets are absorbers rather than reflectors of the beams transmitted to find them, and this task has been made so, at least in part, by the conventional techniques used to suppress background returns.
SUMMARY OF THE INVENTION
According to the present invention, I have developed radar and sonar systems that are indifferent to whether the objects to be found are absorbers, reflectors or refractors of the beams transmitted to detect them.
According to one preferred embodiment of the invention, a dual-beam radar that can illuminate a reflective background such as earth, the sea, clouds, or the ionosphere is fitted with narrow transmit-beam antennas to radar-illuminate that background, receivers that monitor background illumination, processors responsive to local change in that illumination, and a display that highlights those changes. Thus, when a beam from this radar is absorbed, reflected, or refracted by a target, the resulting dark path in the background illumination pattern is displayed as a target.
In this dual-beam embodiment, targets are ranged by triangulation, and one important feature of this invention is a search process in which one beam follows conventional search patterns, and the second intersects with and scans the useful length of the first.
Another important feature of this invention is the way in which target-produced background illumination changes are distinguished from clutter. With conventional radars, the reflections from targets are the returns of interest and the returns from backgrounds are considered clutter, so that stealth-modified targets can hide in chaff or operate in such a way that their returns blend in with those from background, and so avoid detection. In this invention, however, the returns of interest are distinguished from clutter by the order in which they were transmitted, so that these target-masking techniques are ineffective here.
Yet another important feature of the dual-beam embodiment of this invention is a “false alarm” reduction process that does not compromise sensitivity.
This invention is also served by single beam embodiments, and in one such preferred embodiment, a transmitter with a broader beam antenna is dispatched to the far side of the target, the receiver tracking the silhouette of the target in that beam.
These and other features, modifications, and advantages of the radar systems of the present invention are applicable to sonar systems as well, and both radar and sonar embodiments of the present invention will be more fully described with reference to the annexed drawings of the presently preferred embodiments and some of the applications thereof.
REFERENCES:
patent: 4924448 (1990-05-01), Gaer
patent: 5657022 (1997-08-01), Van Etten et al.
patent: 5703593 (1997-12-01), Campbell et al.
patent: 5990822 (1999-11-01), Honigsbaum
“Aspects of UK air defence from 1914 to 1935: some unpublished Admiralty contributions”, Burns, R.W. Science, Measurement and Technology, IEE Proceedings A, vol.: 136 Issue: 6, Nov. 1989, pp. 267-278, 1998.*
“Change detection for target detection and classification in video sequences”, Donohoe, G.W., Acoustics, Speech, and Signal Processing, 1988. ICASSP-88., 1988 International Conference on, 1988, pp. 1084-1087 vol. 2, 1998.*
Introduction to Radar Systems, Skolnik, McGraw-Hill Book Co., (1980) pp. 26, 31, 33, 62-63, 101, 232, 264, 401, 470-3, 552-3.
Cohen & Pontani, Lieberman & Pavane
Sotomayor John B.
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