TARGET IDENTIFICATION METHOD FOR A SYNTHETIC APERATURE RADAR SYSTEM

• US 20100277364A1
• Filed: 06/19/2007
• Published: 11/04/2010
• Est. Priority Date: 06/20/2006
• Status: Active Grant

• Current Assignee: Telespazio SPA (Leonardo S.p.A.)
• Original Assignee: Telespazio SPA (Leonardo S.p.A.)
• Inventors: Ronzitti, Lorenzo, Saitto, Antonio, Mazzenga, Franco
• Granted Patent: US 8,405,539 B2
• Time in Patent Office: Days
• US Class Current: 342/25R
• 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
• CPC Class Codes: G01S 13/9029 specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time

Abstract

In a synthetic aperture radar system (1) monitoring an area containing at least one moving target (2) for identification, the target (2) is equipped with an identification device (3), which receives the radar signal (RS) transmitted by the radar system (1), and transmits a processed radar signal (ES) obtained by modulating the incoming radar signal (RS) with a modulating signal (MODS) containing target (2) information (ID, MSG), such as identification (ID) and status (MSG) information, and by amplifying the modulated radar signal (RS); the radar echo signal (RES) reflected by the monitored area and containing the processed radar signal (ES) is received and processed by a control station (8) of the radar system (1) to locate the target (2) on a map of the monitored area, and to extract the target (2) information (ID, MSG) to identify the target (2).

Claims

1. ) A target (2) identification method for a synthetic aperture radar system (1), the method comprising:

equipping the target (2) with an identification device (3);

receiving, by the identification device (3), a radar signal (RS) transmitted by the radar system (1);

processing, by the identification device (3), the incoming radar signal (RS) to obtain a processed radar signal (ES);

transmitting the processed radar signal (ES) by the identification device (3);

receiving, by the radar system (1), a radar echo signal (RES) comprising the processed radar signal (ES); and

processing the radar echo signal (RES) by the radar system (1) to locate the target (2);

the method being characterized in that processing the incoming radar signal (RS) by the identification device (3) comprises;

assigning target (2) information (ID, MSG) to the incoming radar signal (RS).

2. A method as claimed in claim 1, wherein processing the radar echo signal (RES) by the radar system (1) comprises:

extracting said target (2) information (ID, MSG) from the radar echo signal (RES) to identify the target (2).

3. ) A method as claimed in claim 2, wherein assigning target (2) information (ID, MSG) to the incoming radar signal (RS) by the identification device (3) comprises:

modulating the incoming radar signal (RS) with a modulating signal (MODS) comprising said target (2) information (ID, MSG);

extracting the target (2) information (ID, MSG) from the radar echo signal (RES) by the radar system (1) comprising;

demodulating the radar echo signal (RES).

4. ) A method as claimed in claim 3, wherein processing the incoming radar signal (RS) by the identification device (3) comprises:

amplifying the incoming radar signal (RS).

5. ) A method as claimed in claim 4, wherein the incoming radar signal (RS) is modulated before the incoming radar signal (RS) is amplified.

6. ) A method as claimed in any one of the foregoing claims, wherein processing the incoming radar signal (RS) by the identification device (3) comprises:

encrypting said target (2) information (ID, MSG) by means of a programmable key;

extracting the target (2) information (ID, MSG) from the radar echo signal (RES) by the radar system (1) comprising;

decrypting the target (2) information (ID, MSG) by means of the programmable key.

7. ) A method as claimed in claim 6, wherein said target (2) information (ID, MSG) is encrypted by the identification device (3) before the incoming radar signal (RS) is modulated.

8. ) A method as claimed in claim 6 or 7, wherein said target (2) information (ID, MSG) is decrypted by the radar system (1) after the radar echo signal (RES) is demodulated.

9. ) A method as claimed in any one of claims 3 to 8, wherein processing the incoming radar signal (RS) by the identification device (3) comprises:

detecting the presence of the radar signal (RS); and

only activating modulation of the incoming radar signal (RS) in the presence of the radar signal (RS).

10. ) A method as claimed in any one of the foregoing claims, wherein said target (2) information (ID, MSG) comprises at least an identification code (ID) unequivocally identifying the target (2).

11. ) A method as claimed in any one of the foregoing claims, wherein said target (2) information (ID, MSG) comprises at least one status message (MSG) relative to the status of the target (2).

12. ) A method as claimed in claim 11, wherein said target (2) information (ID, MSG) comprises at least a message sequence comprising a said identification code (ID) and at least one said status message (MSG) following the identification code (ID).

13. ) A method as claimed in claim 12, wherein said target (2) information (ID, MSG) comprises a number of successive repetitions of said message sequence.

14. ) A method as claimed in any one of claims 11 to 13, wherein said identification code (ID) is coded by a respective first sequence of a given first number (NID) of binary digits, each of a given first digit duration (DID);

and said status message (MSG) is coded by a respective second sequence of a given second number (NMSG) of binary digits, each of a given second digit duration (DMSG).

15. ) A method as claimed in claim 14, wherein said second digit duration (DMSG) equals said first digit duration (DID).

16. ) A method as claimed in claim 14 or 15, wherein said radar signal (RS) comprises at least one radar pulse of a given pulse duration (DSAR);

said first digit duration (DID) and said second digit duration (DMSG) being such that the total duration of the binary digits coding said target (2) information (ID, MSG) does not exceed the pulse duration (DSAR).

17. ) A method as claimed in any one of claims 14 to 17, wherein extracting the target (2) information (ID, MSG) from the radar echo signal (RES) by the radar system (1) comprises:

performing a succession of matched-filter demodulations of respective successive portions of the radar echo signal (RES) defined by the digit durations (DID, DMSG) of all the said binary digits coding said target (2) information (ID, MSG).

18. ) A method as claimed in claim 17, wherein assigning said target (2) information (ID, MSG) to the incoming radar signal (RS) by the identification device (3) comprises:

modulating the incoming radar signal (RS) with a modulating signal (MODS) comprising said target (2) information, to obtain a modulated signal (MS);

each of said matched filters being matched to a respective portion of the modulated signal (MS) defined by a corresponding one of said binary digits of said message sequence.

19. ) A target (2) identification device for a synthetic aperture radar system (1), the identification device (3) comprising receiving means (11;

26) for receiving a radar signal (RS) transmitted by the radar system (1);

amplifying means (17) for amplifying the incoming radar signal (RS); and

transmitting means (18;

26) for transmitting a processed radar signal (ES) supplied by said amplifying means (17);

the identification device (3) being characterized by comprising signal processing means (13, 19, 20, 21, 22) for assigning to the incoming radar signal (RS) target (2) information (ID, MSG) allowing identification of the target (2) by the radar system (1).

20. ) A device as claimed in claim 19, wherein said signal processing means (13, 19, 20, 21, 22) comprise modulating means (13) for modulating the incoming radar signal (RS) with a modulating signal (MODS) comprising said target (2) information (ID, MSG).

21. ) A device as claimed in claim 20, wherein said modulating means (13) are connected between said receiving means (11;

26) and said amplifying means (17).

22. ) vice as claimed in claim 20 or 21, wherein said signal processing means (13, 19, 20, 21, 22) comprise encryption means (21) for encrypting said target (2) information (ID, MSG) by means of a programmable key;

and memory means (22) for storing the programmable key.

23. ) A device as claimed in claim 22, wherein said encryption means (21) are connected to the input of said modulating means (13).

24. ) A device as claimed in any one of claims 20 to 23, wherein said signal processing means (13, 19, 20, 21, 22) comprise detecting means (19) connected to the output of said receiving means (11;

26) to detect the presence of the radar signal (RS); and

activating means (20) for connecting the receiving means (11;

26) to the input of said modulating means (13) when commanded by the detecting means (19) detecting the presence of the radar signal (RS).

25. ) A device as claimed in any one of claims 19 to 24, wherein said receiving and transmitting means (11, 18;

26) comprise antenna means (26);

the device comprising selecting means (27) for connecting the antenna means (26) selectively to the input of said signal processing means (13, 19, 20, 21, 22) to receive said radar signal (RS), and to the output of said amplifying means (17) to transmit said processed radar signal (ES).

26. ) A synthetic aperture radar system comprising transmitting means (5) for transmitting a radar signal (RS);

receiving means (6) for receiving a radar echo signal (RES) comprising a processed radar signal (ES) transmitted by an identification device (3) of the type claimed in any one of claims 19 to 25; and

processing means (10) connected to the receiving means (6) to process the radar echo signal (RES), and which are configured to process said processed radar signal (ES) to identify said target (2).

27. ) A system as claimed in claim 26, wherein the processing means (10) comprise demodulating means (24) for demodulating said radar echo signal (RES) to extract said target (2) information (ID, MSG).

28. ) A system as claimed in claim 26 or 27, wherein said processing means (10) comprise decryption means (25) for decrypting said target (2) information (ID, MSG) by means of a programmable key.

29. ). A system as claimed in claim 28, wherein said decryption means (25) are connected to the output of said demodulating means (24).

30. ) A system as claimed in any one of claims 26 to 29, wherein said modulating signal (MODS) comprises a sequence of binary digits for coding said target (2) information (ID, MSG);

the binary digits having respective digit durations (DID, DMSG); and

said demodulating means (24) comprising a number of matched filters, which operate in succession on respective successive portions of the radar echo signal (RES) defined by the digit durations (DID, DMSG).

31. ) A system as claimed in claim 30, wherein said modulating means (13) supply a modulated signal (MS);

each of said matched filters being matched to a respective portion of the modulated signal (MS) defined by the digit duration (DID, DMSG) of a corresponding said binary digit.