Method and apparatus for detecting individuals using electrical field sensors

• US 7,154,275 B2
• Filed: 06/09/2005
• Issued: 12/26/2006
• Est. Priority Date: 12/10/2002
• Status: Expired due to Fees

• 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: Sutphin, Eldon M., Zank, Paul A., Buchanan, David W., Succi, George P.
• Primary Examiner(s): DEB, ANJAN K
• Application Number:
  US11/148,499
• Publication Number:
  US 20060261818A1
• Time in Patent Office: 565 Days
• Field of Search: 324/457, 324/671, 324/686, 340/561
• US Class Current: 324/457
• CPC Class Codes: G01R 29/12 Measuring electrostatic fields or voltage-potential
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence
• CPC Class Codes: G08B 13/26 by proximity of an intruder causing variation in capacitance or inductance of a circuit
• CPC Class Codes: G08B 15/001 Concealed systems, e.g. disguised alarm systems to make covert systems
• CPC Class Codes: G08B 5/38 using flashing light

Abstract

A robust, easily deployable, covert, passive intrusion detection system uses one or more E-field sensors to detect the presence of a moving individual and to provide an indication of the presence of the individual adjacent the sensor based on E-field distortion produced by the individual. Single-ended and differential E-field sensors with noise canceling and a guarding circuit provide sufficient sensitivity, with filtering from 0.5 Hz to 8.0 Hz selecting only human intruders. Either visible or invisible flashing light sources at the sensor indicate the presence of a moving individual at the sensor, thus to provide intruder location without the necessity of providing a geolocation system.

Claims

1. A robust, easily deployable, covert, passive individual intrusion detection system, comprising:

a passive low-power E-field sensor including an ultra-high impedance antenna for sensing electrostatic field; and

,

a processor coupled to said E-field sensor for detecting when a change in sensed E-field exceeds a predetermined threshold, indicative of the presence of an individual adjacent said sensor.

2. The system of claim 1, wherein said E-field sensor is a single-ended sensor.

3. The system of claim 1, wherein said sensor includes two spaced-apart E-field sensors and a differential amplifier coupled to the output of said spaced-apart E-field sensors to develop a differential E-field output, thereby to provide noise-canceling for far-field AC sources.

4. The system of claim 3, and further including an additional pair of orthogonally-oriented E-field sensors having an associated differential amplifier for multi-access bearing detection.

5. The system of claim 1, and further including a light-emitting device at said sensor, said light-emitting device activated when said threshold is exceeded.

6. The system of claim 5, and further including a drive for said light-emitting device for causing said light-emitting device to pulse at a predetermined rate upon said threshold being exceeded.

7. The system of claim 6, wherein said drive activates said light-emitting device at a different pulse rate after said threshold has been first exceeded and then later the sensed change in E-field signal goes below said threshold, thus to indicate that an individual has passed the sensor.

8. The system of claim 5, wherein said light-emitting device emits light in the visible region of the electromagnetic spectrum.

9. The system of claim 5, wherein said light-emitting device emits light in the non-visible region of the electromagnetic spectrum.

10. The system of claim 1, and further including a passband filter coupled to said sensor for passing through E-field change signals having a frequency between 0.5 Hz and 8.0 Hz, thus to sense E-field change due to an individual moving with respect to said sensor and to eliminate detection of E-field change due to non-human sources.

11. The system of claim 1, wherein said sensor includes an antenna lead, and an ultra-high impedance amplifier coupled to said antenna lead, and further including a guarding circuit around said antenna lead, a portion of the output from said amplifier coupled to said guarding circuit such that there is no potential difference between said lead and said guarding circuit, whereby the input capacitance of said ultra-high impedance amplifier is not diminished by any stray capacitance from surrounding circuits or conductors, such that the input to said amplifier is matched to said pad.

12. The system of claim 1, and further including a signature detection circuit for determining from the output of said processor the presence of footsteps, whereby the presence of an individual is determinable and whereby the speed of movement of said individual is determinable.

13. The system of claim 1, and further including a transmitter for transmitting the fact of the exceedance of said threshold to a remote location.

14. The system of claim 1, wherein said sensor and processor are battery powered and further including means for alerting individuals to the presence of an intruder adjacent said sensor, said alerting means being in deep sleep mode until such time as said threshold is exceeded, whereby the operational lifetime of said sensor is increased by limiting current drain during the sensing operation.

15. The system of claim 1, and further including a dart having fins, said sensor and said processor being carried by said dart, such that said dart can be launched to an area to be surveilled, whereby multiple sensors can be readily launched toward and positioned across a surveilled area.

16. A method for determining the presence of an individual in a surveilled area, comprising the steps of:

providing a passive E-field sensor having an ultra-high impedance antenna in the surveilled area for detecting a change in the E-field due to the presence of a moving individual in the vicinity of the E-field sensor; and

,

providing a light-emitting device at the E-field sensor driven to emit light when the presence of an individual has been detected by the E-field sensor, whereby the location of the individual proximate to the sensor may be determined by detection of the position of the emitted light.

17. The method of claim 16, wherein said light-emitting device emits light in the non-visible region of the electromagnetic spectrum, thus to permit covert detection of the individual.

18. The method of claim 16, wherein said light-emitting device emits light in the visible region of the electromagnetic spectrum, thus to alert the individual that his presence has been detected.

19. The method of claim 16, wherein the light-emitting device is pulsed at a predetermined rate upon detection of the presence of an individual near the E-field sensor, thus to indicate the presence and position of the detected individual.

20. The method of claim 19, wherein the pulse rate at which the light-emitting device is driven is changed after detection of the presence of the individual, the changed pulsing drive persisting after the individual has been sensed and moves away from the sensor to indicate where the individual has passed.