Subterranean image generating device and associated method

• US 8,917,199 B2
• Filed: 04/13/2011
• Issued: 12/23/2014
• Est. Priority Date: 04/13/2011
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Samaniego, Raymond, Pilcher, Christopher M., Tomich, John L.
• Primary Examiner(s): Brainard, Timothy A
• Application Number:
  US13/086,107
• Publication Number:
  US 20120262324A1
• Time in Patent Office: 1,350 Days
• Field of Search: 342/22, 342/25
• US Class Current: 342/22
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 13/9043 Forward-looking SAR
• CPC Class Codes: G01S 7/04 Display arrangements
• CPC Class Codes: H01Q 1/3258 using the gutter of the vehicle; Means for clamping a whip aerial on the edge of a part of the vehicle
• CPC Class Codes: H01Q 21/064 using horn or slot aerials slotted waveguides arrays H01Q21/005

Abstract

In certain embodiments, a subterranean imaging apparatus comprises at least two receive channels configured on a land-based vehicle and a synthetic aperture radar (SAR) system. The at least two receive channels are operable to generate electrical signals according to electromagnetic radiation reflected from a subterranean target below a ground surface. The SAR system is operable to receive the electrical signals from the at least two receive channels, generate raw images from the received electrical signals, generate a weighting according to phase statistics of pixels in the raw images, and combine the raw images using the weighting to generate a refined image of the subterranean target.

Claims

1. A subterranean imaging apparatus comprising:

an antenna array comprising a plurality of elements, the plurality of elements configured on a land-bases vehicle; and

a synthetic aperture radar (SAR) system coupled to the antenna array and operable to;

receive electrical signals from the antenna array;

transmit electromagnetic radiation from a first subset of the plurality of elements to a subterranean target below a ground surface, wherein the antenna array has a depression angle selected to generate and transmit the electromagnetic radiation as air waves, lateral waves, and ground waves, wherein the lateral waves are bounded by the ground surface and a critical angle defined by an interface of the ground waves and the lateral waves;

receive electromagnetic radiation reflected from the subterranean target on a second subset of the plurality of elements having a polarity similar to the polarity of the first subset, the electromagnetic radiation having a frequency that ranges from 0.1 to 2.0 Gigahertz;

generate raw images from the electrical signals;

generate a weighting according to phase statistics of pixels in the raw images; and

combine the raw images using the weighting to generate a refined image of the subterranean target,

wherein the antenna array is operable to generate the electrical signals according to the electromagnetic radiation reflected from the subterranean target,

wherein the SAR system is operable to generate the raw images by combining a plurality of the electrical signals at differing positions of the antenna array relative to the subterranean target to determine a position of the subterranean target and positions of features other than the subterranean target below the ground surface.

2. A subterranean imaging apparatus comprising:

at least two receive channels configured on a land-based vehicle; and

a synthetic aperture radar (SAR) system operable to;

receive electrical signals from the at least two receive channels;

generate raw images from the electrical signals;

generate a weighting according to phase statistics of pixels in the raw images; and

combine the raw images using the weighting to generate a refined image of a subterranean target below a ground surface,

wherein the at least two receive channels are operable to generate the electrical signals according to electromagnetic radiation reflected from the subterranean target,

wherein an antenna array comprises the at least two receive channels and the antenna array has a depression angle selected to generate and transmit electromagnetic radiation as air waves, lateral waves, and ground waves, wherein the lateral waves are bounded by the ground surface and critical angle defined by an interface of the ground waves and the lateral waves,

wherein the SAR system is operable to generate the raw images by combining a plurality of the electrical signals at differing positions of the antenna array relative to the subterranean target to determine a position of the subterranean target and positions of features other than the subterranean target below the ground surface.

3. The subterranean imaging apparatus of claim 2, wherein the antenna array includes a plurality of elements.

4. The subterranean imaging apparatus of claim 3, wherein the SAR system is operable to:

transmit a first set of electromagnetic radiation from a first subset of the plurality of elements to the subterranean target; and

receive a first set of electromagnetic radiation reflected from the subterranean target on a second subset of the plurality of elements, the second subset of elements having a polarity similar to the first subset of elements; and

subsequently transmit a second set of electromagnetic radiation from the second subset of elements according to the first set of electromagnetic radiation reflected from the subterranean target; and

receive a second set of electromagnetic radiation reflected from the subterranean target on the first subset of elements.

5. The subterranean imaging apparatus of claim 2, wherein the electromagnetic radiation has a frequency that ranges from 0.1 to 2.0 GigaHertz.

6. The subterranean imaging apparatus of claim 5, wherein the SAR system is operable to:

alternatively transmit the electromagnetic radiation at multiple frequencies within the range of frequencies.

7. The subterranean imaging apparatus of claim 2, wherein the SAR system is operable to:

perform a range gating technique in which the reflected electromagnetic radiation is filtered according to a specified level of latency from transmission of the electromagnetic radiation.

8. The subterranean imaging apparatus of claim 2, further comprising a resistive element coupled between the at least two receive channels and the SAR system, the resistive element operable to reduce the effective Q-factor of the at least two receive channels.

9. The subterranean imaging apparatus of claim 2, wherein the SAR system is operable to:

determine a type of the subterranean target by comparing one or more characteristics of the received electromagnetic radiation with each of a plurality of signatures stored in a memory, each signature comprising the one or more characteristics associated with the type of the subterranean target.

10. A subterranean imaging method comprising:

receiving electrical signals from at least two receive channels configured on a land-based vehicle;

generating raw images from the electrical signals;

generating a weighting according to phase statistics of pixels in the raw images; and

combining the raw images using the weighting to generate a refined image of a subterranean target below a ground surface,

wherein the at least two receive channels are operable to generate the electrical signals according to electromagnetic radiation reflected from the subterranean target,

wherein an antenna array comprises the at least two receive channels and the antenna array has a depression angle selected to generate and transmit electromagnetic radiation as air waves, lateral waves, and ground waves, wherein the lateral waves are bounded by the ground surface and a critical angle defined by an interface of the ground waves and the lateral waves,

wherein a SAR system is operable to generate the raw images by combining a plurality of the electrical signals at differing positions of the antenna array relative to the subterranean target to determine a position of the subterranean target and positions of features other than the subterranean target below the ground surface.

11. The subterranean imaging method of claim 10, wherein receiving the electrical signals from the at least two receive channels comprises receiving the electrical signals from the antenna array, wherein the antenna array includes a plurality of elements.

12. The subterranean imaging method of claim 11, further comprising:

transmitting a first set of electromagnetic radiation from a first subset of the plurality of elements to the subterranean target; and

receive a first set of electromagnetic radiation reflected from the subterranean target on a second subset of the plurality of elements having a polarity similar to the polarity of the first subset of elements; and

subsequently transmitting a second set of electromagnetic radiation from the second subset of elements according to the first set of electromagnetic radiation reflected from the subterranean target; and

receiving a second set of electromagnetic radiation reflected from the subterranean target on the first subset of elements.

13. The subterranean imaging method of claim 10, wherein receiving the electrical signals comprises receiving the electrical signals at a frequency in the range of 0.1 to 2.0 GigaHertz.

14. The subterranean imaging method of claim 13, further comprising:

transmitting electromagnetic radiation at multiple frequencies within the range of frequencies.

15. The subterranean imaging method of claim 10, further comprising:

performing a range gating technique in which the reflected electromagnetic radiation is filtered according to a specified level of latency from transmission of the electromagnetic radiation.

16. The subterranean imaging method of claim 10, further comprising reducing the effective Q-factor of the at least two receive channels using a resistive element coupled between the at least two receive channels and the SAR system.

17. The subterranean imaging method of claim 10, further comprising:

determining a type of the subterranean target by comparing one or more characteristics of the received electromagnetic radiation with each of a plurality of signatures stored in a memory, each signature comprising the one or more characteristics associated with the type of subterranean target.