Guided missile calibration method

• US 5,808,578 A
• Filed: 12/20/1996
• Issued: 09/15/1998
• Est. Priority Date: 12/20/1996
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Davis, Michael A., Carmella, Jeffrey E., Barbella, Peter F., Crawford, Malcolm F., Kaupinis, William M.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/771,787
• Time in Patent Office: 634 Days
• Field of Search: 342/62, 342/77, 342/80, 342/141, 342/149, 342/174, 342/95, 342/97, 342/165, 342/166, 342/169, 342/170, 342/171, 244/3.15, 244/3.19
• US Class Current: 342/62
• CPC Class Codes: F41G 7/003 for seekers using radio waves
• CPC Class Codes: G01S 13/44 Monopulse radar, i.e. simultaneous lobing
• CPC Class Codes: G01S 7/4026 Antenna boresight
• CPC Class Codes: G01S 7/403 in azimuth, i.e. in the horizontal plane
• CPC Class Codes: G01S 7/4034 in elevation, i.e. in the vertical plane

Abstract

A method for calibrating the radar system includes the steps of: replacing stored statistically generated "average" error correction coefficients with error correction coefficients personal to a missile under test. More particularly, stored in the missile'"'"'s memory are: (a) first personalized error correction coefficients generated in response to test signals produced internal to the missile and injected into a monopulse arithmetic unit for the missile'"'"'s receiver/processor; and (b) a second set of personalized error coefficients generated in response to test signals external to the missile and injected through the missile'"'"'s antenna to the receiver/processor. The missile includes a radio frequency (R.F.) energy test signal generator for performing a test during the missile'"'"'s flight to determine "in-flight" personalized error correction coefficients. The test is performed in-flight by injecting the R.F. energy test signal generated internal to the missile during the missile'"'"'s flight into the monopulse arithmetic unit for the receiver/processor. The receiver/processor: (a) compares the first set of error correction coefficients with the "in-flight" error coefficients and adjusts the second set of error correction coefficients in accordance with such comparison; and, (b) if R.F. energy external to the missile is less than a predetermined threshold level, uses the adjusted second set of coefficients during the missile'"'"'s flight to produce boresight error signals; otherwise, the receiver/processor uses unadjusted first set of error correction coefficients.

Claims

1. A guided missile, comprising:

a radar system adapted to generate control signals to guide a missile in response to target radar return signals, such radar system having;

a monopulse antenna adapted to receive radar signals from the target;

a monopulse arithmetic unit coupled to the monopulse antenna for producing a sum signal, an elevation difference signal, and an azimuth difference signal from energy received by the antenna from the target; and

a monopulse receiver/processor for producing boresight error signals in accordance with the monopulse arithmetic unit produced signals and error correction coefficients stored in a memory disposed within the missile, the memory having stored therein;

(a) first personalized error correction coefficients generated in response to test signals produced internal to the missile and injected into the monopulse arithmetic unit for the receiver/processor; and

(b) a second set of personalized error coefficients generated in response to test signals external to the missile and injected through the missile'"'"'s antenna to the receiver/processor.

2. The missile recited in claim 1 including a radio frequency (R.F.) energy test signal generator for performing a test during the missile'"'"'s flight to determine "in-flight" personalized error correction coefficients.

3. The missile recited in claim 2 wherein the missile includes means for injecting the R.F. energy test signal during the missile'"'"'s flight into the monopulse arithmetic unit for the receiver/processor.

4. The missile recited in claim 3 wherein the receiver/processor is adapted to:

(a) compare the first set of error correction coefficients with the "in-flight" error coefficients and adjust the second set of error correction coefficients in accordance with such comparison; and

, (b) if R.F. energy external to the missile is less than a predetermined threshold level, use the adjusted second set of error correction coefficients during the missile'"'"'s flight to produce boresight error signals;

or otherwise, use unadjusted the first set of error correction coefficients.

5. A method for calibrating the radar system, comprising the steps of:

loading software into a memory of the missile, such software including tactical software and statistically generated "average" error correction coefficients;

transmitting a radar test signal through an antenna of the missile to a receiver/processor in the missile to produce "through-the-antenna" personalized error correction coefficients;

re-formatting the software previously loaded into the memory to include the calculated "through-the-antenna" personalized error correction coefficients software; and

loading the re-formatted software into the memory.

6. A method for calibrating the radar system comprising the steps of:

transmitting a radar test signal through a monopulse arithmetic unit internal to the missile to a receiver/processor in the missile to produce personalized error correction coefficients;

writing over previously stored personalized error correction coefficients with the produced internal/factory personalized error correction coefficients.

7. A method for up-grading tactical software in a missile, such missile having stored in a memory therein prior to up-grading previous tactical software stored in a protected, non-externally readable file thereof, and stored in a non-protected, externally readable file thereof personalized error correction coefficients, comprising the steps of:

reading external of the missile the personalized error correction coefficients stored in the memory;

re-formatting up-graded tactical software with the externally read personalized error correction coefficients; and

storing the re-formatted software in the memory.

8. A method for calibrating a radar system adapted to generate control signals for a guided missile, such radar system having:

a monopulse antenna adapted to receive radar signals;

a monopulse arithmetic unit coupled to the monopulse antenna for producing a sum signal, an azimuth difference signal, and an elevation difference signal;

a monopulse receiver/signal processor fed by the sum, azimuth and elevation signals for producing boresight error signals in accordance with such monopulse arithmetic unit produced signals and in accordance with error correction coefficients stored in a memory disposed within the missile, comprising the steps of;

loading software into the memory, such software including tactical software and statistically generated "average" error correction coefficients;

transmitting a radar test signal through the antenna to the receiver/processor;

reading external of the missile, signals produced by the receiver/processor in response to the transmitted test signal and the statistically generated "average" error coefficients stored in the memory;

calculating personalized error correction coefficients for the missile in response to the read signals;

re-formatting the software previously loaded into the memory to include the calculated personalized error correction coefficients software and the tactical software;

loading the re-formatted software into the memory by the loaded software writing over the initially loaded software.

9. A method for calibrating a radar system adapted to generate control signals for a guided missile, such radar system having:

a monopulse antenna adapted to receive radar signals;

a monopulse arithmetic unit coupled to the monopulse antenna for producing a sum signal, an elevation difference signal, and an azimuth difference signal; and

a monopulse receiver/processor producing boresight error signals in accordance with such monopulse arithmetic unit produced signals and error correction coefficients stored in a memory disposed within the missile, comprising the steps of;

loading software into the memory, such software including tactical software and statistically generated default error correction coefficients;

transmitting a radar test signal through the antenna disposed;

reading external of the missile, signals produced by the receiver in response to the transmitted test signal and the statistically generated default error coefficients stored in the memory;

calculating "through-the-antenna" produced personalized error correction coefficients for the missile in response to the read signals;

generating a radar test signal internal to the missile and injecting such test signal into the monopulse arithmetic unit;

measuring signals produced by the receiver in response to the internal test signal;

calculating internally generated personalized error coefficients in response to the internal test signal;

reformatting the software previously loaded into the memory to include the calculated "through-the-antenna" and internally personalized error correction coefficients and the tactical software;

loading the reformatted software into the memory by writing over the initially loaded software.

10. A method for calibrating a radar system adapted to generate control signals for a guided missile, such radar system having:

a monopulse antenna adapted to receive radar signals;

a monopulse arithmetic unit coupled to the monopulse antenna for producing a sum signal, an azimuth difference signal, and an elevation difference signal; and

a monopulse receiver/processor for producing a boresight error signal from the monopulse arithmetic unit produced signals error correction coefficients stored in a memory disposed within the missile, such memory storing tactical software in a protected, non-externally readable section of the memory and non-protected data in an externally readable section of the memory, the error coefficients being stored in the externally readable section of the memory, comprising the steps of;

initiating loading of updated software including updated tactical software into the memory to write over the tactical software previously stored in the memory;

externally reading from the memory the externally readable data from the memory;

storing the error coefficients read from the memory;

re-formatting the updated software with the stored error coefficients; and

loading the re-formatted software into the memory, such loaded software writing over the software stored in the memory.

11. A method for operating a radar system adapted to generate control signals for a guided missile, such radar system having:

a monopulse antenna adapted to receive radar signals from a target;

a monopulse arithmetic unit coupled to the monopulse antenna for producing a sum signal, an elevation difference signal, and an azimuth difference signal from energy received by the antenna from the target; and

a monopulse receiver/processor for producing boresight error signals in accordance with the monopulse arithmetic unit produced signals and error correction coefficients stored in a memory disposed within the missile, comprising the steps of;

performing a first test to determine personalized error coefficients using test signals injected internal to the monopulse arithmetic unit to the receiver/processor and storing such as a first set of personalized error coefficients and performing a second set to determine personalized error coefficients using test signal injected through the antenna to the receiver/processor and storing such as a second set of personalized error coefficients;

performing a test during the missile'"'"'s flight to determine in-flight personalized error coefficients using the test signals internal to the missile injected into the monopulse arithmetic unit to the receiver/processor;

comparing the first set of error correction coefficients with the in-flight error coefficients and adjusting the second set error correction coefficients in accordance with such comparison; and

,

using the adjusted coefficients during the missile'"'"'s flight.

12. A guided missile, comprising:

(a) a radar system adapted to generate control signals to guide such missile in response to target radar return signals, such radar system, comprising;

(i) a monopulse antenna adapted to receive radar signals from the target;

(ii) a monopulse arithmetic unit coupled to the monopulse antenna for producing a sum signal, an elevation difference signal, and an azimuth difference signal from energy received by the antenna from the target;

(iii) a monopulse receiver/processor for producing boresight error signals in accordance with the monopulse arithmetic unit produced signals and error correction coefficients stored in a memory disposed within the missile, such memory having stored therein;

first personalized error coefficients generated in response to test signals injected internal to the monopulse arithmetic unit to the receiver/processor and a second set to determine personalized error coefficients using test signal injected external to the missile through the antenna to the receiver/processor;

(b) test equipment for performing a test during the missile'"'"'s flight to determine in-flight personalized error coefficients using the test signals internal to the missile injected into the monopulse arithmetic unit to the receiver/processor; and

(c) wherein the receiver/processor compares the first set of error correction coefficients with the in-flight error coefficients and adjusting the second set error correction coefficients in accordance with such comparison; and

uses the adjusted coefficients during the missile'"'"'s flight to produce the boresight error signals.