System and methods for detecting change in a monitored environment

• US 7,733,220 B2
• Filed: 10/05/2006
• Issued: 06/08/2010
• Est. Priority Date: 10/05/2006
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Libby, Vibeke
• Primary Examiner(s): GOINS, DAVETTA WOODS
• Application Number:
  US11/543,551
• Publication Number:
  US 20080084295A1
• Time in Patent Office: 1,342 Days
• Field of Search: 340/539.1, 340/539.22, 340/539.23, 340/541, 340/561, 340/565, 340/566, 340/567, 340/501, 340/511, 340/506, 340/517
• US Class Current: 340/539.1
• CPC Class Codes: G08B 13/2494 by interference with electro-magnetic field distribution combined with other electrical sensor means, e.g. microwave detectors combined with other sensor means
• CPC Class Codes: G08B 26/007 Wireless interrogation

Abstract

Systems and methods are provided for detecting changes in a monitored environment. One aspect of the invention relates to a system that comprises a plurality of radio frequency (RF) sensors distributed about the monitored environment, such that each RF sensor configured to respond to an interrogation signal with a unique identifier and a radio frequency (RF) interrogator that transmits interrogation sequences of interrogations signals over a plurality of different frequency bands at one or more power levels. The system also includes a response pattern analyzer that determines response patterns for each of the plurality of RF sensors to the interrogation sequences and transmits a change detection indicator if at least one of the determined response patterns vary outside a predetermined background baseline.

Claims

1. A system for detecting changes in a monitored environment, the system comprising:

a plurality of radio frequency (RF) sensors distributed about the monitored environment, each RF sensor configured to respond to an interrogation signal with a unique identifier;

a radio frequency (RF) interrogator that transmits interrogation sequences of interrogations signals over a plurality of different frequency bands at one or more power levels; and

a response pattern analyzer that determines response patterns for each of the plurality of RF sensors to the interrogation sequences and transmits a change detection indicator if at least one of the determined response patterns vary outside a predetermined background baseline.

2. The system of claim 1, the RF interrogator transmits interrogation sequences of interrogations signals employing spread spectrum frequency hopping to generate pseudo-random frequency bands over different interrogation sequences.

3. The system of claim 1, the predetermined background baseline comprising a plurality of response pattern signatures associated with normal monitoring conditions of the monitored environment, the response pattern analyzer transmits a change detection indicator if the determined response patterns vary outside predetermined thresholds of the plurality or response pattern signatures.

4. The system of claim 1, the predetermined background baseline comprising a plurality of predetermined change thresholds determined based on response patterns received during normal monitoring background conditions of the monitored environment.

5. The system of claim 1, wherein each response pattern is a binary sequence based on valid reads and failed reads for one or more interrogation sequences at one or more power levels.

6. The system of claim 1, wherein the response pattern analyzer comprises:

an RF sensor response pattern storage for storing RF sensor response patterns from the RF interrogator; and

a RF sensor response pattern comparator that compares the stored RF sensor response patterns with the predetermined background baseline.

7. The system of claim 1, wherein the response pattern analyzer transmits a request to the RF interrogator to increase a rate of transmitting interrogation sequences upon detecting a change in the monitored environment.

8. The system of claim 1, wherein the response pattern analyzer tracks movement of an intruder entering the monitored environment upon detecting a change in the monitored environment.

9. The system of claim 1, wherein the response pattern analyzer tracks movement of an intruder entering the monitored environment upon detecting a change in the monitored environment by maintaining and comparing multiple temporary background baselines to determine if the intrusion has ceased if a final background baseline matches a last temporary background baseline.

10. The system of claim 9, wherein the response pattern analyzer compares a last temporary background baseline to the predetermined background baseline to determine if a change has occurred to the monitored environment as a result of the intrusion.

11. The system of claim 1, further comprising one or more movable dithering reflecting plates located between the RF interrogator and at least one of the plurality of RF sensors, and configured to move over different positions to modify the transmission distance, receipt power and/or alter the multi-path effects of the interrogation signals of the RF interrogator and/or response patterns of the at least one of the plurality of RF sensors.

12. A security system for detecting changes in a monitored environment, the system comprising:

a plurality of means for responding to an interrogation signal with a unique identifier, the plurality of means for responding being distributed about the monitored environment;

means for transmitting interrogation sequences of interrogations signals over a plurality of different frequency bands at a plurality of power levels;

means for determining response patterns for each of the plurality of RF sensors to the interrogation sequences;

means for determining if response patterns vary outside a predetermined background baseline; and

means for providing an indication if response patterns vary outside the predetermined background baseline.

13. The system of claim 12, the means for transmitting the interrogation sequences of interrogations signals employing spread spectrum frequency hopping to generate pseudo-random frequency bands over different interrogation sequences.

14. The system of claim 12, the predetermined background baseline comprising a plurality of response pattern signatures associated with normal background monitoring conditions of the monitored environment.

15. The system of claim 12, the predetermined background baseline comprising a plurality of predetermined change thresholds determined based on response patterns received during normal background monitoring conditions of the monitored environment.

16. The system of claim 12, wherein each response pattern is a binary sequence based on valid reads and failed reads for one or more interrogation sequences at one or more power levels.

17. A method for detecting changes in a monitored environment, the method comprising:

distributing a plurality of radio frequency (RF) sensors about the monitored environment, each RF sensor configured to respond to an interrogation signal with a unique identifier;

repeatedly transmitting interrogation sequences of interrogations signals over a plurality of different frequency bands at one or more power levels for a given time period;

determining response patterns for each of the plurality of RF sensors to the interrogation sequences to determine a background baseline;

determining and storing change thresholds from the determined background baseline;

repeatedly transmitting the interrogation sequences of interrogations signals over the plurality of different frequency bands at one or more power levels during a security monitoring time period to determine changes in the monitored environment; and

transmitting a change detection indicator if at least one of the determined response patterns vary outside the change thresholds.

18. The method of claim 17, the site background baseline comprising a plurality of response pattern signatures associated with normal background monitoring conditions of the monitored environment, the change thresholds being associated with variances from the plurality of response pattern signatures.

19. The method of claim 17, the site background baseline comprising a plurality of predetermined change thresholds determined based on response patterns received during normal monitoring conditions of the monitored environment.

20. The method of claim 17, further comprising transmits a request to increase a rate of transmitting interrogation sequences upon detecting a change in the monitored environment.

21. The method of claim 17, further comprising:

tracking movement of an intruder entering the monitored environment upon detecting a change in the monitored environment by maintaining and comparing multiple temporary background baselines to determine if the intrusion has ceased if a final background baseline matches a last temporary site background baseline; and

comparing a last temporary background baseline to the background baseline to determine if a change has occurred to the monitored environment as a result of the intrusion.

22. The method of claim 17, wherein repeatedly transmitting interrogation sequences of interrogations signals over a plurality of different frequency bands at one or more power levels for a given time period further comprises moving at least one reflecting dithering plate to different positions during the interrogation sequences to modify the transmission distance, receipt power and/or alter the multi-path effects of the interrogation signals and/or response patterns of the at least one of the plurality of RF sensors.