Systems and methods for segmenting a satellite field of view for detecting radio frequency signals

• US 9,331,774 B2
• Filed: 06/09/2010
• Issued: 05/03/2016
• Est. Priority Date: 06/09/2010
• Status: Active Grant

• Current Assignee: Exactearth Ltd (Honeywell International Inc.)
• Original Assignee: Exactearth Ltd (Honeywell International Inc.)
• Inventors: Chen, Weiguo, Macikunas, Arunas Gabriel
• Primary Examiner(s): Adams, Tashiana
• Assistant Examiner(s): Mull, Fred H
• Application Number:
  US12/797,066
• Publication Number:
  US 20110304502A1
• Time in Patent Office: 2,155 Days
• US Class Current: 1/1
• CPC Class Codes: G08G 3/02 Anti-collision systems
• CPC Class Codes: H01Q 3/00 Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system means for positioning H01Q1/125
• CPC Class Codes: H04B 7/1851 Systems using a satellite or space-based relay H04B7/18508, H04B7/18521 take precedence; providing specific services H04B7/18523 - H04B7/18576

Abstract

A satellite system for detecting radio frequency signals from space including at least two sensors, a processing unit and at least one receiver. Each sensor receives a plurality of radio frequency signals containing messages and outputs a sensor signal that is representative of the plurality of radio frequency signals. The processing unit selects a predetermined number of mathematical combinations of the sensor signals and combines the sensor signals into the predetermined number of mathematical combinations to produce a plurality of zone signals. The characteristics of each zone signal are undefined at the time the predetermined number of mathematical combinations is selected. The receiver extracts the messages contained in the zone signals.

Claims

1. A satellite system for detecting radio frequency signals from space, the system comprising:

a) at least two sensors, each sensor configured to;

(i) receive a plurality of radio frequency signals, each radio frequency signal comprising at least one message; and

(ii) output a sensor signal that is representative of the plurality of radio frequency signals;

b) a controller configured to;

(i) select a predetermined number of mathematical combinations of the sensor signals;

c) a processing unit that;

(i) receives the sensor signals; and

(ii) produces a plurality of zone signals based on the sensor signals and the predetermined number of mathematical combinations, each zone signal covering a zone that is a portion of the field of view of the satellite system;

d) at least one receiver configured to extract the at least one message contained in the zone signals; and

e) a screening unit coupled to the at least one receiver, the screening unit comprising a processor, with memory and instructions, configured to eliminate duplicate messages and decimate non-duplicate messages from the same source.

2. The satellite system of claim 1, wherein each of the zone signals is at least partially statistically independent from the other zone signals.

3. The satellite system of claim 1, wherein the controller is further configured to adaptively select the mathematical combinations based on (1) at least one of the following:

(a) total signal power of at least one zone signal, (b) bandwidth variations of at least one zone signal, (c) the amplitude distribution of at least one zone signal, (d) the phase distribution of at least one zone signal, (e) an eye diagram of at least one zone signal, (f) the phase trajectory of at least one zone signal, (g) cross-correlation of at least two zone signals, (h) cross covariance of at least two zone signals, and (i) coherency analysis of at least one zone signal, (2) selected time segments of the zone signal, representing one or more message segments, (3) the number of messages extracted from at least one zone signal, and (4) the error rate of at least one zone signal.

4. The satellite system of claim 1, wherein the controller is further configured to select the mathematical combinations from a predefined list of mathematical combinations.

5. The satellite system of claim 1, wherein the screening unit is further configured to select a particular duplicate message for elimination based on the bit error rate of the particular duplicate message.

6. The satellite system of claim 1, wherein the screening unit is further configured to select a particular duplicate message for elimination based on historical data related to the source of the duplicate message.

7. The satellite system of claim 1, further comprising a memory unit configured to store the zone signals prior to sequential processing of the zone signals by the at least one receiver.

8. The satellite system of claim 7, further comprising at least one analog to digital converter configured to convert the zone signals into digital zone signals, the digital zone signals being stored in the memory unit.

9. The satellite system of claim 1, further comprising a plurality of receivers, each receiver configured to extract the at least one message contained in one of the zone signals.

10. The satellite system of claim 1, wherein the at least two sensors have different polarizations.

11. The satellite system of claim 1, wherein the at least two sensors have a field of view and the coverage of each zone signal is less than the field of view of the satellite.

12. The satellite system of claim 1, wherein each sensor is configured to receive radio frequency signals that are automatic identification system (AIS) signals.

13. The system of claim 12, wherein each zone of the zone signals produced by mathematically combining the sensor signals have a number of ships less than a receiver detection threshold.

14. The system of claim 13, wherein the receiver detection threshold is in a range of 800 to 1000 ships.

15. The satellite system of claim 1, wherein the at least two sensors are chosen from monopole antennas, patch antennas, helical antennas or a combination thereof.

16. A method for detecting radio frequency signals from space using a satellite, the method comprising:

a) each of a plurality of sensors receiving a plurality of radio frequency signals, each radio frequency signal comprising at least one message;

b) each of the plurality of sensors outputting a sensor signal representative of the received plurality of radio frequency signals;

c) selecting by a controller a predetermined number of mathematical combinations of the sensor signals;

d) combining by a processing unit the sensor signals into the predetermined number of mathematical combinations to produce a plurality of zone signals, each zone signal covering a zone that is a portion of the field of view of the satellite system;

e) extracting by a receiver the at least one message contained in the zone signals; and

f) decimating non-duplicate messages from the same source.

17. The method of claim 16, wherein each of the zone signals is at least partially statistically independent from the other zone signals.

18. The method of claim 16, wherein the mathematical combinations are adaptively selected based on (1) at least one of:

(a) total signal power of at least one zone signal, (b) bandwidth variations of at least one zone signal, (c) the amplitude distribution of at least one zone signal, (d) the phase distribution of at least one zone signal, (e) an eye diagram of at least one zone signal, (f) the phase trajectory of at least one zone signal, (g) cross-correlation of at least two zone signals, (h) cross covariance of at least two zone signals, and (i) coherency analysis of at least one zone signal, (2) selected time segments of the zone signal, representing one or more message segments, (3) the number of messages extracted from at least one zone signal, and (4) the error rate of at least one zone signal.

19. The method of claim 16, wherein the mathematical combinations are selected from a predefined list of mathematical combinations.

20. The method of claim 16, further comprising eliminating duplicate messages.

21. The method of claim 20, wherein a particular duplicate message is selected for elimination based on the bit error rate of the particular duplicate message.

22. The method of claim 20, wherein a particular duplicate message is selected for elimination based on historical data related to the source of the duplicate message.

23. The method of claim 16, wherein the zone signals are sequentially processed by a single receiver to extract at least one message contained therein.

24. The method of claim 16, wherein the zone signals are concurrently processed by a plurality of receivers to extract the at least one message contained therein.

25. The method of claim 16, wherein the at least two sensors have different polarizations.

26. The method of claim 16, wherein the satellite has a field of view and the coverage of each zone signal is less than the field of view of the satellite.

27. The method of claim 16, wherein the radio frequency signals are automatic identification system (AIS) signals.

28. The method of claim 27, wherein each zone of the zone signals produced by mathematically combining the sensor signals have a number of ships less than a receiver detection threshold.

29. The method of claim 28, wherein the receiver detection threshold is in a range of 800 to 1000 ships.

30. The method of claim 16, wherein the plurality of sensors are chosen from monopole antennas, patch antennas, helical antennas or a combination thereof.

31. A satellite system for detecting radio frequency signals to produce a plurality of zone signals, the system comprising:

a) at least two sensors, each sensor configured to;

(i) receive a plurality of radio frequency signals, each radio frequency signal comprising a plurality of messages, the radio frequency signals being automatic identification system (AIS) signals sent by ships; and

(ii) output a sensor signal that is representative of the received plurality of radio frequency signals;

b) a processing unit that;

(i) receives the sensor signals;

(ii) produces a plurality of zone signals representing zones that segment the field of view of the satellite system based on the sensor signals and an initial set of mathematical combinations of the scanned signals; and

(iii) produces a plurality of zone signals representing zones having adjusted characteristics based on the sensor signals and adjusted mathematical combinations of the scanned signals;

c) a controller configured to;

(i) adaptively select the adjusted mathematical combinations based on characteristics of the zone signals produced by the processing unit; and

(ii) output a control signal relaying the adaptively selected adjusted mathematical combinations to the processing unit; and

d) at least one receiver configured to extract one or more of the plurality of messages contained in the zone signals produced by combining the sensor signals into the adjusted mathematical combinations;

wherein each zone of the zone signals that are produced by mathematically combining the sensor signals have a number of ships less than a receiver detection threshold.

32. The satellite system of claim 31, wherein the controller is configured to adaptively select the adjusted mathematical combinations based on at least a number of messages extracted from at least one zone signal.

33. The satellite system of claim 31, wherein the controller is configured to adaptively select the adjusted mathematical combinations based on at least one of a number of messages extracted from at least one zone signal;

total power of the zone signals;

bandwidth variations of at least one zone signal, amplitude distribution of at least one zone signal;

time slot boundaries;

phase distribution of at least one zone signal;

error rate of at least one zone signal;

an eye diagram of at least one zone signal;

phase trajectory of at least one zone signal;

cross-correlation of at least two zone signal;

cross covariance of at least two zone signals; and

coherency analysis of at least one zone signal.

34. The system of claim 31, wherein the at least two sensors are chosen from monopole antennas, patch antennas, helical antennas or a combination thereof.

35. The system of claim 31, wherein the receiver detection threshold is in a range of 800 to 1000 ships.