Imaging radar suitable for material penetration

• US 5,900,833 A
• Filed: 07/28/1997
• Issued: 05/04/1999
• Est. Priority Date: 04/16/1996
• Status: Expired due to Fees

• Current Assignee: Zircon Corporation
• Original Assignee: Zircon Corporation
• Inventors: Sunlin, William M., Heger, Charles E.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/901,470
• Time in Patent Office: 645 Days
• Field of Search: 342/22, 342/21, 342/25
• US Class Current: 342/22
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 13/89 for mapping or imaging

Abstract

A ground penetrating impulse radar system provides three-dimensional images of targets. A moving array of transmitting and receiving antennas provides narrow beamwidths and high gain by real and synthetic aperture beam processing. Narrow pulsewidth impulse signals are utilized to obtain high resolution. Round trip time is calculated for each three-dimensional pixel in a search volume, and is used to process three dimensional imagery. Analog to digital conversion can be utilized, so all signal processing is accomplished digitally. The radar system is applicable to detecting small objects near the surface by using very narrow pulses, and also can be applied to detect large, deep objects by wider pulses.

Claims

1. An impulse radar system comprising:

a timer;

at least one impulse generator coupled to the timer;

at least one transmitting antenna connected to the at least one impulse generator;

at least one receiving antenna spaced apart from the at least one transmitting antenna;

an analog to digital converter coupled to the at least one receiving antenna;

a signal processor coupled to the analog to digital converter; and

a display coupled to the signal processor.

2. The radar system of claim 1, wherein the signal processor performs synthetic aperture beam processing by motion of the transmitting antenna and receiving antenna relative to a target.

3. The radar system of claim 1, wherein each impulse generator transmits pulses independently by an associated transmitting antenna, and a signal reflected from a target is collected by the receiving antenna.

4. The radar system of claim 1, wherein a received signal from a target is processed by the signal processor by integrating a received signal from all the receiving antennas through time correlation.

5. The radar system of claim 1, wherein a sampler is coupled between the at least one receiving antenna and the analog to digital converter.

6. The radar system of claim 1, wherein the timer has a pulse repetition rate which varies randomly.

7. The radar system of claim 1, further comprising a recorder for storing received signals from the receiving antennas for later processing.

8. The radar system of claim 1, wherein the transmitting antenna transmits radar pulses which penetrate at least one of water, earth, and structures.

9. The radar system of claim 1, wherein the system is a mobile system.

10. The radar system of claim 1, wherein the system is a human portable system.

11. The radar system of claim 1, wherein the system is an airborne system.

12. The radar system of claim 1, wherein there is more than one receiving or transmitting antenna.

13. The radar system of claim 1, further comprising a variable delay circuit coupled between the timer and the impulse generator.

14. The radar system of claim 1, further comprising:

a locator coupled to the signal processor for determining a location of the transmitting and receiving antennas.

15. The radar system of claim 14, wherein the signal processor determines an instantaneous position of the transmitting antenna and receiving antenna from the locator, thereby to determine the signal path length to a particular pixel in the search volume.

16. The radar system of claim 1, wherein the signal processor forms a three dimensional image of the search volume.

17. The radar system of claim 1, wherein the signal processor identifies a return signal from the search volume received by the receiving antenna from each pixel in the search volume as the radar system moves relative to the search volume, and sums the return signals received from each pixel.

18. The radar system of claim 1, further including a second transmitting or receiving antenna, thereby defining a plurality of transmitting-receiving antenna pairs, wherein the signal processor identifies a return signal from the search volume received by each receiving antenna from each pixel in the search volume, and the signal processor sums the return signals for all the transmitting-receiving antenna pairs.

19. The radar system of claim 1, wherein the signal processor calculates a signal path length to each of a plurality of pixels in three dimensions in a search volume, and forms an image of the search volume on the display.

20. A method for detecting a target in a search volume comprising:

transmitting impulse radar pulses from an antenna array including at least one receiving and at least one transmitting antenna spaced apart from the receiving antenna;

receiving a return of the transmittal pulse reflected from the target at the antenna array; and

for each of a plurality of pixel locations in the search volume, accumulating a digital signal representing the return from that location over all the antenna pairs while translating the antenna array across the search volume, thereby providing an indication of a location of the target.

21. The method of claim 20, wherein translating the antenna array includes at least one of manually transporting the antenna array, carrying the antenna array in an aircraft, and carrying the antenna array in a vehicle.

22. The method of claim 20, wherein the accumulating includes sampling the return.

23. The method of claim 20, wherein the transmitting includes randomly varying a repetition rate of the radar pulses.

24. The method of claim 20, wherein the search volume indicates at least one of a volume of earth, water, and a structure.

25. The method of claim 20, wherein there is more than one receiving or transmitting antenna in the array.

26. The method of claim 20, further comprising the providing a variable delay to one of the steps of transmitting or receiving.

27. The method of claim 20, wherein the search volume is a three dimensional search volume.

28. The method of claim 20, wherein the providing an indication of a location of the target further comprises calculating a signal path length to each of the locations in the search volume for each antenna pair, collecting and digitizing a signal representing the path length, and summing the digitized signals for all the antenna pairs.

29. The method of claim 28, wherein the antenna array includes a second transmitting or receiving antenna, thereby defining a plurality of transmitting-receiving antenna pairs.