Method and system for locating a target in an interrogation-response system (IFF)

• US 8,441,392 B2
• Filed: 12/11/2009
• Issued: 05/14/2013
• Est. Priority Date: 12/30/2008
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Descharles, Cyril, Triconnet, Thierry
• Primary Examiner(s): Sotomayor, John B
• Application Number:
  US13/142,724
• Publication Number:
  US 20110309966A1
• Time in Patent Office: 1,250 Days
• Field of Search: 342/42, 342/45, 342/80, 342/125, 342/133, 342139-140, 342146-147, 342149-154, 342/194
• US Class Current: 342/45
• CPC Class Codes: G01S 13/4445 amplitude comparisons monopulse, i.e. comparing the echo signals received by an antenna arrangement with overlapping squinted beams
• CPC Class Codes: G01S 13/4463 using phased arrays
• CPC Class Codes: G01S 13/78 discriminating between different kinds of targets, e.g. IFF-radar, i.e. identification of friend or foe G01S13/75, G01S13/79 take precedence

Abstract

A method and system for locating a target, of azimuth A_estimated^target and of elevation angle S_estimated^target, in space by a carrier uses at least one first antenna array with electronic scanning ARRAY_H and at least one second antenna array with electronic scanning ARRAY_B. The target emits a signal in response to an interrogation from the carrier, each of said antenna arrays includes at least one antenna and the total number of antennas used is at least equal to three.

Claims

1. A method for locating in space, from a carrier, a target of azimuth A_estimated^target and of elevation angle S_estimated^target using at least one first linear antenna array with electronic scanning ARRAY_H comprising at least one individual antenna and at least one second linear antenna array with electronic scanning ARRAY_B comprising at least two individual antennas, said target emitting a signal in response to an interrogation from the carrier, the method comprising:

step 1;

creating a third combined linear antenna array ARRAY_C by coupling at least one individual antenna of the antenna array ARRAY_H and at least one individual antenna of the antenna array ARRAY_B,

step 2;

determining the monopulse angle Ψ

_Rx^H(A,S) or Ψ

_Rx^B(A,S), so as to define a first response acceptance zone ZAR₁, by a measurement on the signal emitted by the target and received on one of the antenna arrays ARRAY_H or ARRAY_B, with A and S being the potential azimuth and elevation angle values of said target,

step 3;

determining the monopulse angle Ψ

_Rx^C(A,S), so as to define a second response acceptance zone ZAR₂, by a measurement on the signal emitted by the target and received on the combined antenna array ARRAY_C, said zone being formed by one or more windows in the plane (A,S),

step 4;

forming, from at least the information items Ψ

_Rx^H(A,S) and Ψ

_Rx^C(A,S) or Ψ

_Rx^B(A,S) and Ψ

_Rx^C(A,S), a third response acceptance zone ZAR₃ equal to the intersection of the two zones ZAR₁ and ZAR₂ defined previously and making it possible to locate the target from its coordinates (A_estimated^target, S_estimated^target).

2. The method according to claim 1, further comprising:

step 5;

forming a fourth response acceptance zone ZAR₄ by eliminating the secondary windows from the zone ZAR₂ by comparison of the signal level received on the antenna array ARRAY_H with that received on the antenna array ARRAY_B via an amplitude discrimination method.

3. The method according to claim 1, further comprising:

step 6;

accurately determining a measurement of the elevation angle S_estimated^target of the target based on the monopulse angles (Ψ

_Rx^K(A,S) Ψ

_Rx^C(A,S)), in which k is to be replaced by B or H, using the following equation;

4. The method according to claim 1, further comprising:

step 7;

accurately determining a measurement of the azimuth A_estimated^target of the target based on the monopulse angles (Ψ

_Rx^K(A,S), Ψ

_Rx^C(A,S)) and on a measurement of the elevation angle S_estimated^target of the target, in which k is to be replaced by B or H, using the following equation;

A_estimated^target=a_(Air,Sir)^kS_estimated^target+b_(Air,Sir)^k(Ψ

_Rx^k(A,S))

in which a_(Air,Sir)^k are parameters dependent on the direction of pointing of the antennas and calculated on the basis of the patterns of said individual antennas used to form the antenna arrays ARRAY_H or ARRAY_B ,

in which b_(Air,Sir)^k(Ψ

_Rx^k(A,S)) are parameters obtained by a polynomial modeling of the trend of the monopulse angle as a function of the azimuth for a fixed elevation angle value, or as a function of the elevation angle for a fixed azimuth value, with k=B or H.

5. The method according to claim 1, wherein the antenna arrays ARRAY_H and ARRAY_B are located on the nose cone of said carrier and that the antenna array ARRAY_H is located vertically to the antenna array ARRAY_B.

6. The method according to claim 1, wherein the interrogation mode from the carrier to the target is an identification friend or foe (IFF) mode.

7. A system for locating a target by a carrier equipped with a primary radar and a secondary radar, the system comprising:

an interrogation-response system which comprises at least a first antenna array a second antenna array, a switching matrix, a beam combiner, a receiver and a computer suitable for implementing the characteristics of the elevation angle and azimuth locating method according to claim 1.