Sensing system and method with integral sensor locating capability

• US 8,570,150 B1
• Filed: 01/07/2009
• Issued: 10/29/2013
• Est. Priority Date: 01/07/2009
• Status: Active Grant

• Current Assignee: L3 Technologies, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Giallorenzi, Thomas R., Lake, Matt, Kingston, Sam, Bowen, Doug
• Primary Examiner(s): Wu, Daniel
• Assistant Examiner(s): BAMERT, JOHN J
• Application Number:
  US12/350,074
• Time in Patent Office: 1,756 Days
• Field of Search: 342/355, 342/422, 342/423, 342/424, 342/444, 342/463, 342/465, 340/8.1, 348143-160
• US Class Current: 340/8.1
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

A sensing system includes integrated sensor locating capability. Sensors can transmit spread spectrum encoded data pulses which are received at mobile nodes. Based on time of arrival information and known locations of the mobile nodes, locations of the sensors can be determined.

Claims

1. A system comprising:

a plurality of sensors, each sensor comprising a transmitter configured to transmit sensor data using a spread spectrum encoded pulse comprising modulated spread sensor data, wherein each sensor further comprises a direct sequence layered spreader configured to output a nested multi-level layered pseudo-noise spreading code that is a product of a first pseudo-noise code multiplied by a second pseudo-noise code, the sensor further comprising a multiplier configured to multiple sensor data by the nested multi-level layered pseudo-noise spreading code to produce the spread sensor data;

a plurality of mobile nodes, wherein each of the plurality of mobile nodes has a known location and comprises a spread spectrum receiver configured to receive spread spectrum encoded pulses and determine a time of arrival of the spread pulse; and

a location calculation unit in communication with each of the plurality of mobile nodes and configured to determine a location of any one of the plurality of sensors using time of arrival information of a transmission from the any one of the plurality of sensors wherein the transmission is received by at least three of the plurality of mobile nodes wherein the spread spectrum receiver of each of the plurality of mobile nodes comprises a layered despreader,

wherein the direct sequence layered spreader comprises;

an A code generator configured to generate, at a clock rate equal to a chip rate of the first pseudo-noise code, the first pseudo-noise code having a length of P_A chips;

a B code generator configured to generate at a clock rate equal to 1/P_A of the chip rate of the first pseudo-noise code, the second pseudo-noise code having a length of P_B chips, wherein “

\”

is mathematical division.

2. The system of claim 1, wherein the sensor is mobile.

3. The system of claim 1, wherein the sensor has no radio frequency receiver.

4. The system of claim 1, wherein the direct sequence layered spreader provides a spread factor of 40 dB or greater.

5. The system of claim 1, wherein the sensor is configured to transmit using a duty cycle of less than 1 percent.

6. The system of claim 1, wherein the sensor is configured to transmit using a duty cycle of less than 0.01 percent.

7. The system of claim 1, wherein the sensor is configured to transmit using a chipping rate of at least 100 MHz.

8. The system of claim 1, wherein the location calculation unit is disposed on one of the plurality of mobile nodes.

9. The system of claim 1, wherein the location calculation unit is configured to perform at least one of multilateration and triangulation.

10. The system of claim 1, wherein the direct sequence layered spreader further comprises a multiplier configured to multiply the first pseudo-noise code by the second pseudo-noise code to produce the nested multi-level layered pseudo-noise spreading code.

11. The system of claim 1, wherein the direct sequence layered spreader further comprises:

a C code generator configured to generate, at a clock rate equal to 1/(PA*PB) of the chip rate of first pseudo-noise code, a third pseudo-noise code having a length of P_C chips; and

multipliers configured to multiply the first pseudo-noise code by the second pseudo-noise code and the third pseudo-noise code to produce the nested multi-level pseudo-noise spreading code,

wherein “

\”

is mathematical division and “

*”

is mathematical multiplication.

12. A system for determining a sensor location comprising:

means for transmitting a spread spectrum encoded pulse from a sensor, the spread spectrum encoded pulse comprising modulated spread sensor data, wherein the means for transmitting comprises a direct sequence layered spreader configured to output a nested multi-level layered pseudo-noise spreading code that is a product of a first pseudo-noise code multiplied by a second pseudo-noise code, the means for transmitting further comprising a multiplier configured to multiple sensor data by the nested multi-level layered pseudo-noise spreading code to produce the spread sensor data;

means for receiving the pulse at a plurality of different, varying locations, the locations being known;

means for determining a time of arrival of the pulse at each of the plurality of different, varying locations; and

means for computing a location of the sensor based on the time of arrival of the spread pulse at each of the plurality of different, varying locations,

wherein the direct sequence layered spreader comprises;

an A code generator configured to generate, at a clock rate equal to a chip rate of the first pseudo-noise code, the first pseudo-noise code having a length of P_A chips;

a B code generator configured to generate at a clock rate equal to 1/P of the chip rate of the first pseudo-noise code, the second pseudo-noise code having a length of P_B chips, wherein “

\”

is mathematical division.

13. The system of claim 12, wherein the layered direct sequence spreading code has a processing gain of at least 40 dB, a chipping rate of at least 10 MHz, and a duty cycle of less than 0.01 percent.

14. The system of claim 12, wherein the direct sequence layered spreader further comprises a multiplier configured to multiply the first pseudo-noise code by the second pseudo-noise code to produce the nested multi-level layered pseudo-noise spreading code.

15. The system of claim 12, wherein the direct sequence layered spreader further comprises:

a C code generator configured to generate, at a clock rate equal to 1/(PA*PB) of the chip rate of first pseudo-noise code, a third pseudo-noise code having a length of P_C chips; and

multipliers configured to multiply the first pseudo-noise code by the second pseudo-noise code and the third pseudo-noise code to produce the nested multi-level pseudo-noise spreading code,

wherein “

\”

is mathematical division and “

*”

is mathematical multiplication.

16. A method of determining a sensor location comprising:

generating in a sensor a nested multi-level layered pseudo-noise spreading code that is a product of a first pseudo-noise code multiplied by a second pseudo-noise code;

multiplying in the sensor data by the nested multi-level layered pseudo-noise spreading code to produce spread sensor data;

transmitting a spread spectrum encoded pulse from the sensor, the spread spectrum encoded pulse comprising the spread sensor data modulated for transmission;

receiving the spread spectrum encoded pulse at a plurality of mobile receivers, wherein each mobile receiver has a known location;

determining a time of arrival of the spread spectrum encoded pulse at each of the plurality of mobile receivers by correlating at each said mobile receiver the spread spectrum encoded pulse received at the mobile receiver;

computing a location of the sensor based on the time of arrival of the spread pulse at each of the plurality of mobile receivers; and

decoding the sensor data at at least one of the plurality of mobile receivers, wherein the receiving comprises performing a layered correlation.

17. The method of claim 16, wherein the layered direct sequence spreading code has an overall spreading factor of 40 dB or greater.

18. The method of claim 16, wherein the transmitting comprises transmitting a pulse having a duty cycle of less than 1 percent.

19. The method of claim 16, wherein the transmitting uses a chipping rate of at least 100 MHz.

20. The method of claim 19, wherein the determining a time of arrival is performed with an accuracy of 10 ns or better.

21. The method of claim 16, wherein the computing a location is performed with an accuracy of 3 meter or better relative to the locations of the mobile receivers.

22. The method of claim 16, wherein the sensor is mobile.

23. The method of claim 22, wherein the sensor has no knowledge of a current position of the sensor.

24. The method of claim 16, wherein the sensor has no knowledge of time of day.

25. The method of claim 16, wherein the computing a location of the sensor comprises performing multilateration using differences between the time of arrival of the spread pulse at each of the plurality of mobile receivers.

26. The method of claim 16, wherein the computing a location of the sensor comprises:

determining a propagation delay between the sensor and each of the plurality of receivers based on a transmission time of the spread spectrum encoded pulse; and

computing the location of the sensor using triangulation based on the propagation delay between the sensor and each of the plurality of receivers.

27. The method of claim 16, wherein the transmitting is initiated in response to a predefined sensor condition.

28. The method of claim 16, wherein the transmitting is repeated at a pseudorandom time interval.

29. The method of claim 16, further comprising using the location of the sensor to point an antenna toward the sensor.

30. The method of claim 16, further comprising using the location of the sensor to point a camera in the vicinity of the sensor.

31. The method of claim 16, wherein the generating step comprises:

generating at a clock rate equal to a chip rate of the first pseudo-noise code the first pseudo-noise code having a length of P_A chips;

generating at a clock rate equal to 1/P_A of the chip rate of first pseudo-noise code the second pseudo-noise code having a length of P_B chips, wherein “

\”

is mathematical division.

32. The method of claim 31, wherein the generating step further comprises multiplying the first pseudo-noise code by the second pseudo-noise code to produce the nested multi-level layered pseudo-noise spreading code.

33. The method of claim 31, wherein the generating step further comprises:

generating at a clock rate equal to 1/(PA*PB) of the chip rate of first pseudo-noise code a third pseudo-noise code having a length of P_C chips; and

multiplying the first pseudo-noise code by the second pseudo-noise code and the third pseudo-noise code to produce the nested multi-level pseudo-noise spreading code,

wherein “

\”

is mathematical division and “

*”

is mathematical multiplication.