Method of and device for detecting the presence of a living being of a particular species in a space monitored by a doppler sensor

• US 5,760,687 A
• Filed: 02/21/1997
• Issued: 06/02/1998
• Est. Priority Date: 02/21/1996
• Status: Expired due to Fees

• Current Assignee: Legrand (Legrand SA), Legrand Snc (Legrand SA)
• Original Assignee: Legrand (Legrand SA), Legrand Snc (Legrand SA)
• Inventors: Cousy, Jean-Pierre
• Primary Examiner(s): Hofsass, Jeffery A.
• Assistant Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US08/803,747
• Time in Patent Office: 466 Days
• Field of Search: 340/554, 367/93, 367/94, 342/27, 342/28
• US Class Current: 340/554
• CPC Class Codes: G01S 13/56 for presence detection presence detection using near field arrangements G01V3/00, e.g. G01V3/08, G01V3/12; burglar, theft or intruder alarms with electrical actuation G08B13/22 - G08B13/26
• CPC Class Codes: G01S 7/415 Identification of targets based on measurements of movement associated with the target

Abstract

The signal delivered by a Doppler sensor is treated after amplification, filtering and digitization by: means for determining the global energy of the digitized signal; autocorrelation test means for showing up a dominant frequency; a filter for rejecting that frequency; comparators for eliminating signals having energy less than a threshold; a filter for isolating a particular frequency band; and means for intercorrelation with a reference signal held in memory.

Claims

1. A method of detecting the presence of a living being of a particular species, in a monitored space in which there is disposed a microwave Doppler sensor supplying a low-frequency signal produced by beating between a transmitted wave and a reflected wave frequency shifted by the Doppler-Fizeau effect by a moving target in the monitored space, wherein said signal from said sensor, after any necessary amplification and filtering, is digitized and processed to show up in the frequency spectrum of said signal peculiarities specific to the species of said living being in order to recognize the presence of a being of that species, and wherein the processing of said digitized signal comprises the following steps:

a) determining the overall energy of said digitized signal and eliminating signals with energy less than a threshold energy;

b) applying to the signal produced by step (a) at least one autocorrelation test adapted to detect the presence of a dominant frequency;

c) filtering said digitized signal by means of an adaptive filter adjusted to reject said dominant frequency detected in step (b);

d) determining the global energy of said signal produced by said filtering step (c) and eliminating signals having energy less than a threshold energy;

e) filtering the signal from step (d) to isolate a particular frequency band that is stable and specific to movements of the particular species of said living being;

f) applying to the signal from step (e) a test of temporal intercorrelation with a reference signal specific to the particular species of said living being and held in memory to define an interspectral energy and emitting at least one two-state signal corresponding to interspectral energies respectively greater than and less than a threshold energy.

2. The method claimed in claim 1 wherein said autocorrelation test in step (b) is a double autocorrelation test.

3. The method claimed in claim 2 wherein steps (b) and (c) are reiterated until dominant frequencies are eliminated before advancing to step (d).

4. The method claimed in claim 1 wherein, between steps (a) and (b), there is inserted a step (a'"'"') in which the global energy of said signal is normalized.

5. The method claimed in claim 1 wherein between steps (d) and (e) there is inserted a step (d'"'"') in which the global energy of said signal is normalized.

6. The method claimed in claim 1 wherein in step (e) said signal is passed through an appropriately adjusted filter.

7. The method claimed in claim 1 wherein between steps (e) and (f) there is inserted a step (e'"'"') in which the global energy of said signal is normalized.

13. The method claimed in claim 1, wherein said living being is a human being.

8. A device for detecting the presence of a living being of a particular species, in a monitored space, of enhanced selectivity, including a microwave Doppler sensor adapted to supply a low-frequency signal dependent on movements of a target relative to the sensor and produced by beating between a transmitted wave and a wave reflected by a moving target in said monitored space, means for digitizing said signal from said sensor after any necessary amplification and filtering, processor means including a microprocessor with associated programs and at least one memory, for appropriately formatting and comparing said digitized signal with reference signals to detect in the frequency spectrum of said signal from said sensor peculiarities specific to the particular species of said living being, which device comprises:

(m)--means for determining the energy of said digitized signal and eliminating signals with energy less than a threshold energy,

(n)--means for applying to the signal from the previous means at least one autocorrelation test adapted to show up the presence of a dominant frequency,

(p)--an adaptive first filter receiving at its input said digitized signal and adjusted to reject said dominant frequency detected by said autocorrelation test,

(q)--comparator means for determining the global energy of the signal filtered by said adaptive first filter and capable of eliminating signals with global energy less than a threshold,

(r)--a second filter receiving said signal from said comparator means and adjusted to isolate a particular frequency band that is stable and specific to movements of the particular species of said living being, and

(s)--means for applying to said signal, reduced to said particular frequency band, a temporal test of intercorrelation with a reference signal held in memory and specific to the particular species of said living being, the test defining an interspectral energy, and for emitting at least one two-state signal corresponding to an interspectral energy respectively greater than and less than a threshold.

9. The device claimed in claim 8 wherein said energy determining and signal elimination means, said autocorrelation test means, said first filter, said comparator means, said second filter and said temporal autocorrelation test means are implemented in the form of appropriate computation programs associated with said microprocessor and executed in sequence.

10. The device claimed in claim 8 wherein said Doppler sensor (1) emits at the frequency of 9.9 GHz.

11. The device claimed in claim 8 wherein said reference signal corresponds to lateral displacement of a human being at a distance of 3 m from said Doppler sensor at a speed of 1.4 m/s.

12. An application of a device as claimed in claim 8 to detecting the intrusion of a person into a protected space.

14. The device claimed in claim 8, wherein said living being is a human being.