RADAR CABLE DETECTION SYSTEM

• US 20100214152A1
• Filed: 05/29/2008
• Published: 08/26/2010
• Est. Priority Date: 05/29/2007
• Status: Active Grant

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Huang, Tom T., Chu, Samson, Kanagawa, Ronnie H., Choe, Yongsu B.
• Granted Patent: US 7,839,321 B2
• Time in Patent Office: Days
• US Class Current: 342/29
• CPC Class Codes: G01S 13/222 using random or pseudorandom pulse repetition frequency
• CPC Class Codes: G01S 13/288 phase modulated
• CPC Class Codes: G01S 13/933 of aircraft or spacecraft
• CPC Class Codes: G01S 7/025 involving the transmission of linearly polarised waves
• CPC Class Codes: G01S 7/414 Discriminating targets with respect to background clutter

Abstract

Ground clutter is effectively separated from true signals echoed by a cable in the flight path of an aircraft, by encoding a transmitted pulse wave in a radar system with at least one transmit (TX) coding sequence, so that received signals echoed by the cable on which the pulse is incident and associated ground clutter are orthogonal or separable from one another. The TX coding sequence is altered into two receive (RX) coding sequences one of which corresponds to the cable and the other to the ground clutter. The two RX coding sequences are then correlated with the received signals, thereby separating the true signals echoed by the cable from the associated ground clutter.

Claims

1. A process for separating ground clutter from signals echoed by a cable in the flight path of an aircraft having a radar system, comprising:

encoding a transmitted pulse wave in the radar system with at least one transmit (TX) coding sequence, so that received signals echoed by a cable on which the pulse is incident and associated ground clutter are orthogonal or separable from one another;

altering the TX coding sequence into two receive (RX) coding sequences one of which corresponds to the cable and the other to the ground clutter; and

correlating the two RX coding sequences with the received signals, thereby separating received signals echoed by the cable from the associated ground clutter.

2. The process of claim 1, including modulating the transmitted pulse wave according to a first TX coding sequence.

3. The process of claim 2, wherein the modulating step includes changing the phase of the transmitted pulse wave.

4. The process of claim 1, including switching the polarization of the transmitted pulse wave between horizontal and vertical according to a second TX coding sequence.

5. The process of claim 1, including modulating the transmitted pulse wave according to a first TX coding sequence, and switching the polarization of the transmitted pulse wave between horizontal and vertical according to a second TX coding sequence.

6. The process of claim 3, wherein the second TX coding sequence switches the polarization of the transmitted pulse wave so that the wave is coded to spread over the duration of the pulse, and received signals echoed by a cable on which the wave is incident have a different polarization spread than the associated ground clutter.

7. The process of claim 1, including extracting non-stationary structure in an echo correlation vector produced in the radar system to correspond with a target cable, and subtracting the non-stationary structure from the echo correlation vector, thereby improving a signal-to-noise ratio (SNR) for detection of a target cable having a relatively low radar cross section (RCS).

8. The process of claim 6, wherein the extracting step is performed by using a running median with adaptation on end bins.

9. The process of claim 1, including determining an approaching speed of a target cable according to received signals echoed by the cable.

10. The process of claim 1, including reducing false target detections by introducing a random time jitter between successive ones of the transmitted pulse waves.

11. The process of claim 1, including providing a radar altimeter as the radar system in the aircraft, mounting a forward looking antenna array on the aircraft, and coupling the antenna array to a RF port of the radar altimeter.

12. The process of claim 11, including coupling the antenna array to the radar altimeter through an up/down converter.

13. The process of claim 1, including radiating the transmitted pulse wave via a forward looking transmit antenna on the aircraft.

14. The process of claim 1, including receiving the signals echoed by a cable and the associated ground clutter via a forward looking receive antenna on the aircraft.

15. The process of claim 1, including radiating the transmitted pulse wave via a common forward looking system antenna on the aircraft, receiving the signals echoed by a cable and the associated ground clutter via the common system antenna, and isolating successive transmitted pulse waves and the received signals from one another.