System and method for obtaining precise missile range information for semiactive missile systems

• US 6,204,801 B1
• Filed: 08/14/1998
• Issued: 03/20/2001
• Est. Priority Date: 08/14/1998
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Meltzer, Harvey J., Sharka, David
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US09/134,024
• Time in Patent Office: 949 Days
• Field of Search: 342/62, 342/73, 342/82, 342/83, 342/84, 342/85, 342/86, 342/87, 342/88, 342/90, 342/97, 342/98, 342/99, 342/103, 342/105, 342/106, 342/109, 342/112, 342/114, 342/115, 342/119, 342/128, 342/129, 342/130
• US Class Current: 342/62
• CPC Class Codes: F41G 7/2266 Systems comparing signals received from a base station and reflected from the target
• CPC Class Codes: F41G 7/2286 using radio waves
• CPC Class Codes: F42C 13/045 using transmission of F.M. waves
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems

Abstract

A system (10) for determining the range between a missile (14) and a target (18) adapted for use with a semi-active missile system. The system (10) includes a first circuit (12) for generating a periodic signal (24) that is periodically frequency modulated. A second circuit (16) determines a closing rate at which the missile 14 is approaching the target 18 via the periodic signal 24. A third circuit (16) determines a value containing information corresponding to the range and the closing rate via the periodic signal. A fourth circuit (16) determines the range from the closing rate and the value. In a specific embodiment, the first circuit (12) includes an illumination system (12). The illumination system (12) includes a periodically modulated carrier signal generator (32) that generates the periodic signal (24). The periodically modulated carrier signal generator (32) includes a frequency source, a frequency modulator, and an illumination system computer. The illumination system computer runs software for adjusting the modulation parameters of the frequency modulator. The second, third and fourth circuits (16) are included in a receiver system (16) onboard the missile (14). The receiver system (16) includes a front receiver located near the front of the missile and a rear receiver located near the rear of the missile (14). A receiver system computer runs software that implements the fourth circuit (16). The receiver system (16) includes a local oscillator for providing a reference frequency for the receiver system. The local oscillator derives the reference frequency from the periodic signal provided by the first circuit. In illustrative embodiment, the fourth circuit (16) runs computer software that subtracts the closing rate from the combination of closing rate and range and provides the range in response thereto.

Claims

1. A system for determining the distance between a missile and a target comprising:

first means for generating a periodic signal, said signal frequency modulated at a predetermined rate;

second means for determining a closing rate at which said missile is approaching said target via said periodic signal;

third means for determining a value containing information corresponding to said distance and said closing rate via said periodic signal; and

fourth means for determining said distance from said closing rate and said value.

2. The invention of claim 1 wherein said first means includes an illumination system.

3. The invention of claim 2 wherein said periodic signal is a radio frequency signal.

4. The invention of claim 2 wherein said illumination system is a microwave illumination system.

5. The invention of claim 2 wherein said illumination system includes a periodically modulated carrier signal generator for generating said periodic signal.

6. The invention of claim 5 wherein said periodically modulated carrier signal generator includes a frequency source, a frequency modulator, and an illumination system computer.

7. The invention of claim 5 wherein said illumination system computer runs software for adjusting the modulation parameters of said frequency modulator.

8. The invention of claim 1 wherein said second means includes Doppler means for measuring a Doppler shift representative of said closing rate based on a first portion of said periodic signal, said first portion characterized by a first frequency.

9. The invention of claim 1 wherein said third means includes time shift means for measuring a time delay between the reception of a second portion of said periodic signal by a receiver system in said missile and the reception by said receiver system of said second portion after reflection from said target, said second portion characterized by a second frequency.

10. The invention of claim 9 wherein said value is proportional to said time delay.

11. The invention of claim 9 wherein said receiver system includes a front receiver located near the front of said missile and a rear receiver located near the rear of said missile.

12. The invention of claim 11 wherein said missile system further includes a computer.

13. The invention of claim 12 wherein said computer runs software for implementing said fourth means.

14. The invention of claim 12 wherein said computer is a pre-existing missile borne computer.

15. The invention of claim 11 wherein said receiver system includes a local oscillator for providing a reference frequency for said receiver system.

16. The invention of claim 15 wherein said reference frequency is derived by said local oscillator from said periodic signal provided by said first means.

17. The invention of claim 15 wherein said local oscillator includes a phase-locked loop for locking to said periodic signal and providing said reference signal in response thereto.

18. The invention of claim 1 wherein said fourth means includes computer software for subtracting said closing rate from said value and providing said distance in response thereto.

19. The invention of claim 1 wherein said missile includes a receiver system.

20. The invention of claim 19 wherein said receiver system includes a computer in communication with a rear receiver and a rear local oscillator.

21. The invention of claim 20 wherein said rear local oscillator includes a phase-locked loop.

22. The invention of claim 20 wherein said rear receiver and said rear local oscillator are connected to a downconverter in said receiver system.

23. The invention of claim 22 wherein a front receiver and said rear receiver provide input to said downconverter.

24. The invention of claim 23 wherein said rear local oscillator provides a reference frequency to said downconverter, said downconverter outputting a downconverted signal in response thereto.

25. The invention of claim 24 wherein a Fast Fourier Transform circuit receives said downconverted signal and outputs a processed signal in response thereto to said computer.

26. The invention of claim 1 wherein said first means includes an illumination system having a computer in communication with a frequency source and a frequency modulator.

27. The invention of claim 26 wherein said frequency source is a radio frequency source.

28. The invention of claim 26 wherein outputs of said frequency source and said frequency modulator are input to a combiner the output of which is connected to a transmitter.

29. The invention of claim 28 wherein said computer runs software for controlling the frequency of said frequency source, and modulation parameters of said frequency modulator.

30. A system for determining the distance between a missile and a target comprising:

first means for generating a periodic signal, said periodic signal having a first component of a first constant frequency and a second component of a second varying frequency;

second means for determining a closing rate at which said missile is approaching said target from said first component; and

third means for determining a value containing information corresponding to said distance between said missile and said target and said closing rate via said second component; and

fourth means for determining said distance from said closing rate and said value.

31. A method for determining the distance between a missile and a target comprising the steps of:

generating a periodic signal frequency modulated at a predetermined rate;

measuring a closing rate at which said missile is approaching said periodic signal;

determining a value containing information corresponding to said distance between said missile and said target and said closing rate via said periodic signal; and

calculating said distance from said closing rate and said value.

32. A semi-active missile system capable of accurately determining the distance between a missile and a target comprising:

an illumination source for outputting a first periodically modulated carrier signal;

a receiver system located on said missile and having a front and rear receiver for receiving a reflected periodically modulated carrier signal, and said first periodically modulated carrier signal, respectively;

a first software routine running on a computer, said first software routine for calculating a missile target closing rate from a non-modulated portion of said first periodically modulated carrier signal, and a non-modulated portion of said reflected periodically modulated carrier signal received by said receiver system;

a second software routine running on said computer, said second software routine for obtaining a value representative of a combination of missile target closing rate and said distance from a modulated portions of said first periodically modulated carrier signal and said reflected periodically modulated carrier signal received by said receiver system;

a third routine running on said computer for extracting said distance from said value using said missile target closing rate;

a missile propulsion system;

a missile steering system;

a guidance processor for controlling said missile propulsion system and said missile steering system to guide said missile, said guidance processor utilizing said distance to optimize missile performance; and

an intercept arm function for using said distance to selectively activate the arming of said missile in response to said distance being within a predetermined distance threshold.