IDENTIFICATION FRIEND OR FOE (IFF) SYSTEM

• US 20100309039A1
• Filed: 06/03/2010
• Published: 12/09/2010
• Est. Priority Date: 06/03/2009
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Powell, Thomas H., Rivers, Cornelia F.
• Granted Patent: US 8,325,081 B2
• Time in Patent Office: Days
• US Class Current: 342/42
• CPC Class Codes: G01S 13/781 Secondary Surveillance Radar [SSR] in general

Abstract

A method and apparatus for reducing transponder responses to reflected signals utilizes data in an interrogator message to confirm that if two interrogations are received within a predetermined period of time and if the two interrogator signals correspond to a side lobe followed by a reflected main beam signal, the presence of multipath reflection can be correctly identified and the reply to the main beam interrogation can be suppressed.

Claims

1. A transponder comprising:

a linear receiver configured to receive one or more interrogator signals;

an analog-to-digital converter (ADC) having an input configured to receive an analog signal from said linear receiver and having an output at which a digital signal is provided;

a digital processor configured to receive digital signals provided thereto from said ADC and to utilize data in an interrogator signal to confirm that if two interrogator signals are received within a predetermined period of time and if the first interrogator signal corresponds to a side lobe interrogator signal and the second interrogator signal corresponds to a reflected main beam signal, said digital processor suppresses transmission of a reply signal by the transponder.

2. The transponder of claim 1 wherein the predetermined period of time is in the range of about 1 microsecond to about 14 microseconds and any two microsecond increment therebetween.

4. The apparatus of claim 1 wherein said signal processor for suppressing transmission of a reply signal comprises:

a detector for determining if two interrogator signals are received within a predetermined period of time;

a detector for determining if a first received interrogator signal corresponds to a side lobe interrogator signal and a second received interrogator signal corresponds to a reflected main beam signal corresponding to the first interrogator signal.

3. A transponder comprising:

(a) a receiver for receive one or more interrogator signals; and

(b) a signal processor for suppressing transmission of a transponder reply signal in response to two interrogator signals being received within a predetermined period of time with a first received interrogator signal corresponding to a side lobe interrogator signal and a second received interrogator signal corresponding to a reflected main beam signal.

5. A method for determining whether a transponder should reply to an interrogator signal, the method comprising:

(a) determining if two interrogator signals are received at the transponder within a predetermined period of time;

(b) determining if a first received interrogator signal corresponds to a side lobe interrogator signal and a second received interrogator signal corresponds to a reflected version of the first received signal.

6. The method of claim 5 wherein (a) is performed before (b).

7. The method of claim 5 further comprising determining if a second received interrogator signal corresponds to a reflected version of the first received signal.

8. The apparatus of claim 7 wherein the second interrogator signal corresponds to a reflected main beam signal.

9. The method of claim 7 wherein determining if a second received interrogator signal corresponds to a reflected version of the first received signal comprises determining if the first and second interrogator signals have the same wave form codes.