Method and system for detecting radar signals

• US 8,179,825 B2
• Filed: 12/23/2005
• Issued: 05/15/2012
• Est. Priority Date: 05/12/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Smith, Adrian, Steer, David
• Primary Examiner(s): Ton, Dang T
• Assistant Examiner(s): O CONNOR, BRIAN T
• Application Number:
  US11/315,292
• Publication Number:
  US 20060258296A1
• Time in Patent Office: 2,335 Days
• Field of Search: 370/310, 370/329, 370/332, 370/338, 370/343, 370/431, 370/445, 445/63.1, 445/67.13, 342/57, 342/159
• US Class Current: 370/310
• CPC Class Codes: G01S 7/021 Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals
• CPC Class Codes: H04K 2203/36 including means for exchanging jamming data between transmitter and receiver, e.g. in forward or backward direction
• CPC Class Codes: H04K 3/224 with countermeasures at transmission and/or reception of the jammed signal, e.g. stopping operation of transmitter or receiver, nulling or enhancing transmitted power in direction of or at frequency of jammer
• CPC Class Codes: H04K 3/226 Selection of non-jammed channel for communication spectrum sharing arrangements H04W16/14; selection of wireless resources by user or terminal H04W72/02
• CPC Class Codes: H04K 3/822 by detecting the presence of a surveillance, interception or detection
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks

Abstract

A method and system for detecting RADAR signals in a radio communications system is provided. A detection system includes a pulse examination. Based on the result from the examination/analysis, a RADAR pulse is detected. The examination/analysis may include a correlator for correlating received pulses with themselves or samples previously obtained.

Claims

1. A system for detecting a RADAR signal in a communications network which utilizes signals different from the RADAR signal, the system comprising:

a receiver for receiving a first pulse;

a self-correlator for measuring a self-correlation of the first pulse with a non-zero time offset copy of the first pulse;

a comparator for comparing the self-correlation measurement with a threshold that is set from expected correlation of receiver noise; and

a detector for determining that the first pulse is a RADAR pulse when the self-correlation measurement is lower than the threshold that is set from expected correlation of receiver noise.

2. A system according to claim 1, further comprising:

a correlator for measuring the correlation of the first pulse with predefined pulses,

the RADAR pulse being detected based on the self-correlation measurement and the correlation measurement.

3. A system according to claim 1, wherein the self-correlator correlates samples of the first pulse with themselves at a pluriaty of non-zero time offsets, the average of the self-correlation measurements at the plurality of non-zero time offsets being compared with the threshold by the comparator.

4. A system according to claim 1, further comprising:

a memory circuit for logging a newly received pulse for later use in searching for periodicities corresponding to a RADAR signal.

5. A system according to claim 1, wherein a plurality of communications nodes form the communications network, with at least two of the communications nodes having the self-correlator, the detector or a combination thereof.

6. A system according to claim 2, further comprising:

a memory system for storing one or more pulse sequences including an externally detected pulse sequence, the pulse sequence being used as the predefined pulses.

7. A system according to claim 3, wherein a self-correlation at a zero time offset is measured by the self-correlator, a ratio of the non-zero time offset average to the self-correlation measurement at the zero time offset being compared with the threshold by the comparator.

8. A system according to claim 5, wherein the system further comprises:

a processor for determining an action of the communications nodes in response to the detection of the RADAR pulse.

9. A system according to claim 6, further comprising:

a circuit for examining one or more characteristics of the first pulse,

wherein the detector detects the RADAR pulse based on the output from the comparator, or the output from the comparator and the one or more characteristics.

10. A system according to claim 7, wherein the memory system includes:

a selector for selectively storing the pulse sequence into the memory system.

11. A system according to claim 6, wherein the memory system includes:

an encryption module for encrypting the pulse sequence before storing, and

a decryption module for decrypting data stored in the memory system for the correlation.

12. A system according to claim 6, wherein the first pulse is stored in the memory system when its self-correlation measurement is low.

13. A system according to claim 8, wherein the detection of the RADAR pulse is exchanged between the communications nodes for channel sharing.

14. A system according to claim 9 wherein the detector coordinates the actions of the self-correlator, the circuit and the memory system.

15. A system according to claim 9, further comprising:

a correlator for measuring the correlation of the first pulse with externally obtained pre-defined pulses.

16. A system according to claim 9, wherein the circuit includes:

a measurement module for measuring the one or more characteristics of the first pulse, and/or

a header detector for detecting a header or a standardized signature signal that identifies the format of a communications transmission.

17. A system according to claim 9, wherein the circuit includes:

a circuit for implementing pattern matching to the first pulse.

18. A system according to claim 11, wherein the memory system comprises:

a first memory section for storing encrypted data, and

a second memory section for storing data other than the encrypted data.

20. A system according to claim 15, wherein the self-correlator, the correlator or a combination thereof is enabled based on the examination result.

21. A system according to claim 9, further comprising:

a memory system having a memory for storing information for the pattern matching.

19. A system according to claim , wherein the memory system uses a key selector for randomly selecting one or more keys from the pulse received at the receiver.

22. A system according to claim 19, wherein the memory system includes a key storage for storing the one or more keys.

23. A method of detecting a RADAR signal in a communications network which utilizes signals different from the RADAR signal, the method comprising the steps of:

receiving a first pulse by a receiver;

measuring a self correlation of the first pulse with a non-zero time offset copy of the first pulse;

comparing the self-correlation measurement with a threshold that is set from expected correlation of receiver noise;

when the self-correlation measurement is lower than the threshold that is set from expected correlation of receiver noise, determining that the first pulse is a RADAR pulse.

24. A method according to claim 23, further comprising the step of:

examining one or more characteristics of the first pulse,

the self-correlation measurement being implemented based on the examination result.

25. A method according to claim 23, further comprising the step of:

logging a newly received pulse for later use in searching for periodicities corresponding to a RADAR signal.

26. A method according to claim 23, further comprising:

correlating the first pulse with pre-defined RADAR pulses in a memory.

27. A method according to claim 23, wherein a plurality of communications nodes form the communications network, and further comprising the step of:

at a communications node, initiating a new action of the communications node in response to the detection of the RADAR pulse.

28. A method according to claim 23, wherein a plurality of communications nodes form the communications network, and further comprising the step of:

among the communications nodes, exchanging the self-correlation measurement, the detection of the RADAR pulse, or a combination thereof.

29. A method according to claim 24, further comprising:

measuring a self-correlation of the first pulse at a plurality of non-zero time offsets and calculating the average of the self-correlation measurements at the plurality of non-zero time offsets;

measuring a self-correlation of the first pulse at a zero time offset and calculating a ratio of the non-zero time offset average to the self-correlation measurement at the zero time offset,

the determining step implementing the determination based on the comparison between the average or the ratio and the threshold.

30. A method according to claim 26, further comprising:

examining one or more characteristics of the first pulse.

31. A method according to claim 29, further comprising the step of:

storing the first pulse in a memory when the self-correlation measurement is low.

32. A method according to claim 30, wherein the step of correlating the first pulse with pre-defined RADAR pulses is implemented based on the examination result.