Method and apparatus for through-the-wall motion detection using CW radar
AssigneeBAE Systems Information and Electronic Systems Integation Inc.
InventorsPaul D. Zemany, Eldon M. Sutphin
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Abstract
A CW radar (10) is used to detect motion of objects (22) behind a wall (20) by projecting a radar beam through the wall and by measuring the returns from the objects behind the wall, with a change in the phase difference between the transmitted and received CW signals providing an indication of motion behind the wall and thus the presence of an individual.
Claims19
A method for detecting the presence of an individual behind a wail, comprising the steps of:
- projecting CW radar signal through a wall;
- detecting portions of the CW radar signal returned by an object behind the wall;
- determining the phase difference between projected and returned CW radar signals to generate a phase difference signal;
- sampling the phase difference signal;
- thresholding the sampled signal;
- and,
- detecting when the sampled signal exceeds the threshold, thus to indicate the presence of a moving individual, whereby individuals moving behind the wall can be detected.
Apparatus for the detection of a moving individual behind a wall, comprising:
- a frequency source;
- a power divider coupled to said frequency source for outputting as a first output a CW signal of one predetermined magnitude for forming a radar beam and for outputting as a second output a CW signal of a diminished magnitude;
- a circulator coupled to said first output;
- an antenna coupled to said circulator for transmitting a CW radar beam towards said wall and for detecting radar returns from objects behind said wall;
- a mixer coupled to said second output and said circulator for deriving a phase difference signal representing the phase difference between transmitted and returned signals at said antenna;
- a sampling circuit for sampling the said phase difference signal;
- a thresholding circuit for thresholding said sampled signal;
- a detector for detecting when said sampled signal exceeds said threshold, thus to indicate the presence of a moving object behind said wall;
- and,
- a transmitter for transmitting the fact of the detection of a moving object to a remote location.
A system of determining the presence of an individual behind a wall, comprising:
- a CW radar having a directional antenna adapted to project CW radar energy through said wall, and detecting returns from objects behind said wall;
- a phase difference detector for detecting when the phase difference between CW energy directed through said wall and energy returned from objects behind said wall exceeds a predetermined threshold indicating the presence of a moving object behind said wall,
- a transmitter for transmitting the fact of threshold exceedance to a remote location.
Dependencies are inferred from the claim text.