Moving multi-polarization multi-transmitter/receiver ground penetrating radar system and signal processing for buried target detection

Patent metadata

Field	Value
Publication number	US-9395437-B2
Application number	US-201313911134-A
Country	US
Kind code	B2
Filing date	Jun 6, 2013
Priority date	Jun 6, 2013
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

A moving ground penetrating radar is comprised of multiple transmitters and receivers with multiple, e.g., Horizontal and Vertical, polarizations to detect buried targets with standoff capability. Novel signal and imaging techniques are used to form high quality radar imagery with low artifacts that are due to various sources of self-induced resonances, e.g., transmitter-receiver coupling, calibration errors, and motion errors in the multi transmitter/receiver channels of the radar system. The irradiated target area image is formed via exploiting both the spatial diversity of the physical multi-transmitter and multi-receiver array and synthetic aperture/array that is generated by the motion of the platform that carries the radar system. The images that are formed from the multiple polarizations are combined to remove surface targets/clutter and, thus, enhance signatures of buried targets.

First claim

What is claimed is:

1. A method of standoff detection for surface and buried targets in or on the road side of a ground vehicle using RF impulse signal, the method comprising the steps of:
transmitting a sequence of RF impulse signals by using at least one impulse generator paired with a respective transmit antenna while the vehicle moves forward on the road, said transmit antenna being placed at the center of an antenna frame in either horizontal or vertical polarization, the antenna frame being mounted on an articulable telescope boom of the vehicle to enable the radar to be configured for different scanning modes;
receiving the return of impulse RF signals using an array of Vivaldi notch antennas, each regularly disposed as either horizontal or vertical polarization with respect to the antenna frame;
converting the impulse signals received from the Vivaldi notch antennas in analog format to digital format using a digitizer to digitize the analog signal as radar data;
interleaving the converted radar data with header and trailer to incorporate GPS information with the radar data;
processing the stream of radar data along with the GPS information to produce radar images for storage in computer memory as multi-transmitter/receiver channel images; and
calibration of said multi-transmitter/receiver channel images based on:
a system model for uncalibrated reconstructed images in a multi-transmitter and multi-receiver radar on a moving platform, wherein
ƒ lM ( x m ,y n ,φ l )=ƒ l ( x m −x ls ,y n −y ls )exp( jφ l ),

where (x ls , y ls ) represents an unknown shift in a spatial domain, and φ l is an unknown phase; and
an iterative correlation-based phase and time-delay estimation algorithm to calibrate multi-transmitter/receiver images using a reference image that is generated from the mean value of the multi-transmitter/receiver images in each iteration.

2. A method of standoff detection for surface and buried targets in or on the road side of a ground vehicle using RF impulse signal, the method comprising the steps of:
transmitting a sequence of RF impulse signals by using at least one impulse generator paired with a respective transmit antenna while the vehicle moves forward on the road, said transmit antenna being placed at the center of an antenna frame in either horizontal or vertical polarization, the antenna frame being mounted on an articulable telescope boom of the vehicle to enable the radar to be configured for different scanning modes;
receiving the return of impulse RF signals using an array of Vivaldi notch antennas, each regularly disposed as either horizontal or vertical polarization with respect to the antenna frame;
converting the impulse signals received from the Vivaldi notch antennas in analog format to digital format using a digitizer to digitize the analog signal as radar data;
interleaving the converted radar data with header and trailer to incorporate GPS information with the radar data;
processing the stream of radar data along with the GPS information to produce radar images for storage in computer memory; and
multi-transmitter/receiver image enhancement via t-score weighting that generates an enhanced full-resolution image based on t-score weighting of a mean reconstructed image.

3. A method of standoff detection for surface and buried targets in or on the road side of a ground vehicle using RF impulse signal, the method comprising the steps of:
transmitting a sequence of RF impulse signals by using at least one impulse generator paired with a respective transmit antenna while the vehicle moves forward on the road, said transmit antenna being placed at the center of an antenna frame in either horizontal or vertical polarization, the antenna frame being mounted on an articulable telescope boom of the vehicle to enable the radar to be configured for different scanning modes;
receiving the return of impulse RF signals using an array of Vivaldi notch antennas, each regularly disposed as either horizontal or vertical polarization with respect to the antenna frame;
converting the impulse signals received from the Vivaldi notch antennas in analog format to digital format using a digitizer to digitize the analog signal as radar data;
interleaving the converted radar data with header and trailer to incorporate GPS information with the radar data;
processing the stream of radar data along with the GPS information to produce radar images for storage in computer memory;
optimizing signal returns for surface and buried targets based on:
placing the transmit antennas in either horizontal or vertical polarization for transmitting impulse RF signal,
using two different sets of Vivaldi antennas for receiving the returned impulse RF signals, the first set of Vivaldi antennas, which has the frequency range from 200 MHz to 3000 MHz, is oriented in the vertical polarization, the second set of Vivaldi antennas, which has frequency range from 500 MHz to 3000 MHz, is oriented in the horizontal polarization,
interleaving the location of the receive Vivaldi antennas, wherein the first antenna in the array is from the first set, and the second antenna is from the second set, and wherein the pattern of configuration is repeated for the rest of the receiving antennas in the antenna array, and
collecting antenna data output for image processing, wherein the transmit and two types of receive antennas are spatially-diversified, some of which have H polarization and others with V polarization, wherein
coherent complex four images that are formed from four polarizations, that is, VV, VH, HV and HH, are fused via an adaptive filtering method to suppress the surface targets/clutter while enhancing the signatures of buried targets, the adaptive filtering method comprising:
a continuous-domain multidimensional signal model and its discrete version to relate multi-polarization;
a localized adaptive filtering method based on LSSP to calibrate two images at different polarizations;
a forward and backward LSSP approach to create a difference image or SSD image, that represents changes or buried targets in the two images at different polarizations; and
a spatially-varying version of LSSP, global signal subspace processing, to calibrate two images at different polarizations using a 2D spatially-varying filter that produces an SSD image that does contain boundary artifacts between the subpatches that are used in LSSP.

4. The method of standoff detection according to claim 3 , wherein said continuous-domain multidimensional signal model and its discrete version to relate multi-polarization via a two-dimensional linear spatially-varying are for VV and VH images.

5. The method of standoff detection according to claim 3 , comprising:
simultaneously transmitting two different and uncorrelated pulses or waveforms using radar transmitters with different polarizations; and
matched filtering to separate the resultant echoes that are generated via illumination of the target area with the two uncorrelated transmissions at the Horizontal and Vertical polarizations.

6. The method of standoff detection according to claim 5 , wherein said two different and uncorrelated pulses or waveforms have horizontal and vertical polarizations.

7. The method of standoff detection signal processing module according to claim 5 , wherein said pulses are uncorrelated in time such that their cross-correlation is zero for all relative time delays of the two pulses.

Assignees

• Us Army

Inventors

• Ton Tuan T
• Wong David C
• Soumekh Mehrdad

Classifications

• G01S13/867

  Combination of radar systems with cameras · CPC title

• G01S13/86

  Combinations of radar systems with non-radar systems, e.g. sonar, direction finder · CPC title

• G01S7/4004

  of parts of a radar system · CPC title

• G01S13/0209

  Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband · CPC title

• G01S13/885 Primary

  for ground probing (prospecting or detecting using electromagnetic waves G01V3/12) · CPC title