Method and system for through-the-wall imaging using sparse inversion for blind multi-path elimination

Patent metadata

Field	Value
Publication number	US-9335408-B2
Application number	US-201313947426-A
Country	US
Kind code	B2
Filing date	Jul 22, 2013
Priority date	Jul 22, 2013
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

Targets are detected in a scene behind a wall by first transmitting a pulse through the wall. Then, a primary impulse response is detected by a sparse regularized least squares inversion applied to received signals corresponding to the reflected pulse. A delay operator that matches the primary impulse response to similar impulse responses in the received signals is also determined. A distortion of the pulse after the pulse passes through the wall but before the pulse is reflected by the target can also be determined. The distortion is used in an iterative process to refine the detection of the target and to suppress ghosting artifacts.

First claim

I claim:

1. A system for detecting a target in a scene behind a wall, comprising:
an antenna array arranged approximately parallel to a front of the wall;
a transmitter configured to transmit a pulse through the wall;
a receiver configured to receive received signals reflected by the target through the wall in response to transmitting the pulse;
means for detecting a primary impulse response by a sparse regularized least squares inversion based on the pulse and the received signals; and
means for determining a delay operator that matches the primary impulse response to similar impulse responses in the received signals.

2. The system of claim 1 , wherein a distortion of the pulse is estimated after the pulse passes through the wall but before the pulse is reflected by the target.

3. The system of claim 1 , wherein the pulse is an ultrawide band signal, and the received signals are received by a linear array of antenna elements, wherein one or more elements of the array are used to transmit the pulse.

4. The system of claim 3 , wherein the antenna elements are subsampled randomly with as many as 80% of the antenna array elements randomly switched OFF.

5. The system of claim 1 , wherein the received signals include the primary impulse response received via a direct path, and secondary impulse responses received by multi-paths.

6. The system of claim 1 , wherein the scene behind the wall is sparse in an image domain, and the primary response is sparse in a time domain, and wherein the image domain is incoherent with the time domain.

7. The system of claim 1 , wherein the target is imaged using the primary pulse and the delay.

8. The system of claim 1 , wherein the delay operator is a sequence of weighted Dirac delta functions.

9. The system of claim 1 , wherein clutter induced by internal wall reflections is removed without knowledge of physical properties or geometric characteristics of the scene and wall.

10. The system of claim 1 , wherein the primary impulse response is detected in an image domain and the delay operator is determined in a time domain.

11. The system of claim 1 , wherein the delay operator identifies multipath reflections corresponding to secondary impulse responses.

Assignees

• Mitsubishi Electric Res Lab

Inventors

• Mansour Hassan

Classifications

• G01S3/74

  Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals (systems in which the directions of different signals are determined sequentially and displayed simultaneously G01S3/04, G01S3/14) · CPC title

• G01S13/888 Primary

  through wall detection · CPC title

• G01S7/292

  Extracting wanted echo-signals · CPC title

• G01S13/89

  for mapping or imaging · CPC title