Detector of objects by microwave frequency echo analysis

• US 7,259,571 B2
• Filed: 05/17/2006
• Issued: 08/21/2007
• Est. Priority Date: 05/24/2005
• Status: Expired due to Fees

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Lehureau, Jean-Claude, Millet, Nicolas
• Primary Examiner(s): Benson; Walter
• Application Number:
  US11/435,281
• Publication Number:
  US 20070001689A1
• Time in Patent Office: 461 Days
• Field of Search: 324/639, 324/637
• US Class Current: 324/639
• CPC Class Codes: G01N 22/00 Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more G01N3/00 - G01N17/00, G01N24/00 take precedence
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G01V 8/005 operating with millimetre waves, e.g. measuring the black losey radiation

Abstract

The field of the invention is that of devices for detecting non-metallic objects concealed on human subjects. These devices are more particularly dedicated to the surveillance and protection of reserved access areas, such as airport areas. The device according to the invention comprises a portable detector comprising a transmitter and a receiver of microwave frequency signals disposed in an enclosure of chaotic geometry including a plurality of measurement holes. The microwave frequency signal measured by this detector depends on the nature of the objects disposed under the holes. A processing device linked to this detector is used to correlate the measured signals with prerecorded signals. When the correlation exceeds a certain threshold corresponding to the presence of suspect objects, an alarm is generated.

Claims

1. A device for detecting dielectric objects on a human body comprising:

a detector with an enclosure in which are disposed a wave transmitter transmitting a microwave frequency signal and a microwave frequency receiver, said enclosure including a measurement surface intended to be positioned in the vicinity of said human body, wherein said enclosure is highly reflective to the waves transmitted by the transmitter, has a chaotic type geometry for said waves and wherein the measurement surface includes at least two holes, wherein the dimensions of the cavity of the enclosure measuring a few centimeters.

2. The detection device as claimed in claim 1, wherein the structure includes a single transmitter also serving as the receiver.

3. The detection device as claimed in claim 1, wherein the enclosure has essentially flat walls.

4. The detection device as claimed in claim 3, wherein flat reflectors are disposed inside the enclosure.

5. The detection device as claimed in claim 4, wherein a dielectric guide links the transmitter and the receiver so as to provide a reference signal to the receiver.

6. The detection device as claimed in claim 3, wherein a dielectric guide links the transmitter and the receiver so as to provide a reference signal to the receiver.

7. The detection device as claimed in claim 1, wherein waveguides are disposed in line with the holes to facilitate the leakage of the waves transmitted by the transmitter towards the outside of the enclosure.

8. The detection device as claimed in claim 1, wherein the structure is portable and includes, a handle.

9. The detection device as claimed in claim 1, wherein the spectrum of the transmitted signal is located in the 18 to 40 gigahertz frequency range.

10. The detection device as claimed in claim 1, wherein the device also includes a data processing system comprising:

memorizing means prerecording signals corresponding to the various open or closed states of the holes;

acquiring means for receiving the signals received by the detector;

processing means for processing said received signals;

correlating means for correlating said processed signals with the various prerecorded signals;

warning means for warning when the correlation ratio between a processed signal and at least one of the prerecorded signals exceeds a critical threshold, said warning means being audible or visual.

11. A method of detecting dielectric objects on a human body from a detection device as claimed in claim 10, comprising the following steps:

producing of prerecorded received signals S_PE corresponding to the different open or closed states of the holes;

positioning of the detector in the vicinity of a human body to be analyzed;

acquising of the received signal corresponding to this location of the detector and processing of said received signal;

correlating of said processed signal with the various prerecorded signals S_PE,

transmitting of a warning signal when the correlation ratio between the processed signal and at least one of the prerecorded signals exceeds a critical threshold.

12. The detection method as claimed in claim 10, wherein said producing step includes the following substeps:

with the holes of the enclosure all open, transmission of a frequency ramp by the transmitter;

recording of the received signal denoted enclosure-frequency-signal S_PE corresponding to said transmission signal;

with at least one of the holes closed, transmitting of a frequency ramp by the transmitter;

recording of the received frequency signal denoted hole-frequency-signal S_FTcorresponding to said transmission signal;

calculating of a prerecorded signal S_PE obtained by subtraction of the enclosure-frequency-signal S_FE from the hole-frequency-signal S_FT;

executing said transmitting, recording and calculating steps for the various open or closed states of the holes so as to obtain the various prerecorded signals.

13. The detection method as claimed in claim 12, wherein the third step includes the following substeps:

transmitting of a frequency ramp by the transmitter;

recording of the received frequency signal called measurement-frequency-signal corresponding to said transmission signal;

calculating of the processed signal obtained by subtraction of the enclosure-frequency-signal from the measurement-frequency-signal.

14. The detection method as claimed in claim 11, wherein the third step includes the following substeps:

transmitting of a frequency ramp by the transmitter;

recording of the received frequency signal called measurement-frequency-signal corresponding to said transmission signal;

calculating of the processed signal obtained by subtraction of the enclosure-frequency-signal from the measurement-frequency-signal.