Abstract:
An apparatus and method for protecting against incoming projectiles comprising transmitting two radar waveforms, the first waveform comprising a pulsed continuous wave waveform, and the second waveform comprising a pulsed linear chirp waveform over a bandwidth, and based on returned radar data, causing deployment of a defense mechanism to intercept a detected incoming projectile.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of the filing of U.S. Provisional Patent Application Ser. No. 60/985,336, entitled “Electronic Curtain for Vehicle Protection”, filed on Nov. 5, 2007, and the specification and claims thereof are incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     Not Applicable. 
     COPYRIGHTED MATERIAL 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention (Technical Field) 
     The present invention relates to methods and apparatuses for protecting vehicles or other targets from projectiles such as rocket-propelled grenades. 
     2. Description of Related Art 
     There is a pressing need for anti-Rocket Propelled Grenade protection systems. Some system components are available, including a low velocity pellet defense system that is cued by an optical sensor. It can give good directional information, but has no provision to give the accurate range information needed to generate the very precise timing signal to work correctly. The present invention provides a millimeter wave electronic curtain based on radar with much reduced signal processing requirements to provide this signal. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is of an apparatus and method for protecting against incoming projectiles, comprising: transmitting two radar waveforms, the first waveform comprising a pulsed continuous wave waveform, and the second waveform comprising a pulsed linear chirp waveform over a bandwidth; and based on returned radar data, causing deployment of a defense mechanism to intercept a detected incoming projectile. In the preferred embodiment, deployment occurs on detection of an amplitude peak distinct from that of ground clutter. Preferably, the waveforms are interleaved, the first waveform employs high pulse repitition frequency, and the bandwidth is at least approximately 500 MHz (most preferably about 500 MHz). 
     Further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings: 
         FIG. 1  is a schematic diagram of the apparatus and method of the invention; and 
         FIG. 2  is a plot of range versus velocity versus amplitude showing a ridge clearly separated from stationary clutter and thus readily detectable. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is of a method and apparatus for detecting a high velocity projectile and, upon detection, taking active countermeasures. The invention preferably employs a dual waveform implemented in digitally controlled adaptable radar. The first waveform is preferably a pulsed continuous wave (CW) waveform providing detection and velocity measurement capability over a wide variation in initial range to the target, but with only moderate range resolution. The second waveform detects targets only over a very narrow variation in range, but provides extremely accurate range resolution to control fusing. The purpose of the dual waveform is to implement both detection and precise fusing the same low cost radar. Multiple polarizations are preferably used to help discriminate targets from clutter. 
     Tracking is ordinarily required to assure that a proximity fuse is not triggered by other objects entering its field of regard. The proximity fuse detonates the warhead at the correct time when the tracked target reaches a precisely calculated range. 
     The present invention takes advantage of highly flexible digital waveform control to preferably implement both functions in one piece of hardware. The initial waveform, a high pulse repitition frequency (HPRF), pulsed CW waveform, detects and identifies the target, providing initial range, velocity, acceleration, and estimated time and speed of arrival. With this information, tracking of the target becomes unnecessary. The second waveform, preferably a pulsed linear chirp waveform over a wide bandwidth (typically 500 MHz or more), sets up an “electronic curtain” at a desired range. This waveform detects a target over a very narrow set of ranges only, but provides very precise range and velocity information on targets entering this set of ranges. When the desired target “pierces the curtain”, this velocity information in conjunction with the previous estimates of time and velocity at arrival are used to assure that it is the correct target and to trigger the weapon&#39;s warhead. Because one only needs to examine a small range swath and the target always has a very high velocity, one can use very narrow filters and very small data sets to detect the approaching projectile. 
       FIG. 1  shows the invention  10  in schematic form, with optional distances indicated. Radar system  24  generates the waveforms and detects and processes the return signals. A radar window  16  is established, capturing incoming projectiles (such as from a rocket-propelled grenade launcher  12  and passing through optional break screen  14  along a flight path  26  with positive velocity  18 . Upon detection of a signal  34  such as shown in  FIG. 2  (distinguished from ground clutter  32 ), the radar system can direct deployment of one or more active countermeasures  22  (such as pellets ejected with negative velocity  20 ). 
     Countermeasures other than deployment of pellets include those now known or known in the future in the art, including firing of a high-powered laser, firing of an intercepting missile (with or without explosive effect), deployment of a physical barrier, deployment of electronic countermeasures, and firing of a pulsed energy weapon. 
     Note that in the specification and claims, “about” or “approximately” means within twenty percent (20%) of the numerical amount cited. 
     Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference.