System and method of radar detection of non linear interfaces

• US 20030179126A1
• Filed: 01/31/2002
• Published: 09/25/2003
• Est. Priority Date: 09/27/2000
• Status: Active Grant

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Ko, Harvey W, White, David M, Oursler, Douglas A, Jablonski, Daniel G., Smith, Dexter G
• Granted Patent: US 6,765,527 B2
• Time in Patent Office: Days
• US Class Current: 342/22
• CPC Class Codes: G01N 22/00 Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more G01N3/00 - G01N17/00, G01N24/00 take precedence
• CPC Class Codes: G01S 13/347 using more than one modulation frequency
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 7/41 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G01S 7/411 Identification of targets based on measurements of radar reflectivity G01S7/415 takes precedence

Abstract

A harmonic radar nonlinear junction detector system for detecting concealed weapons, electronics, and other man-made objects utilizing state-of-the art wireless technology, circuit fabrication, signal synthesis, and computer processing techniques to detect and characterize man-made objects possessing nonlinear junctions. The system transmits a pair of low power waveforms and a receiver within the system is coherently tuned to harmonics of the transmitted frequencies of the waveforms to detect man-made metal objects and electronics that contain non-linear junctions. The receiver is also capable of receiving inter-modulation products reflected from the man-made objects that are a result of using two incident signals. The system uses two signal sources generating user-definable waveforms of variable frequencies in order to provide enhanced discrimination and target identification abilities via the processing of returned inter-modulation products.

Claims

1. A system for detecting and characterizing man-made objects that possess nonlinear junctions in which incident signals are transmitted into free space, and upon contact with said man-made objects that possess nonlinear junctions, said man-made objects that possess nonlinear junctions will reflect new signals that can be received and characterized, said system comprising:

a first signal generator that generates a first incident signal, f₁;

a second signal generator that generates a second incident signal, f₂;

transmit circuitry that transmits said first signal, f₁, and said second signal, f₂;

receive circuitry that is tuned to receive signals that are exact harmonic multiples of said incident signals, f₁ and f₂, and is also tuned to receive inter-modulation products that are reflected from said man-made objects that possess nonlinear junctions as a result of said man-made objects being illuminated by said incident signals f₁ and f₂;

an antenna assembly coupled with said transmit and receive circuitry that assists in the transmission of said incident signals, f₁ and f₂, and the reception of reflected signals from said man-made objects that possess nonlinear junctions;

a signal processor that processes said received reflected signals from said man-made objects that possess nonlinear junctions, such that the man-made objects can be characterized according to their composition;

a master clock that synchronizes said first signal generator, said second signal generator, said receive circuitry, said transmit circuitry, and said signal processor; and

a data bus that couples said master clock, said first signal generator, said second signal generator, said receive circuitry, said transmit circuitry, and said signal processor together.

2. The system of claim 1 in which the antenna assembly is comprised of:

a high frequency directional array antenna; and

a low frequency omni-directional array antenna.

3. The system of claim 1 wherein said first signal generator generates a first incident signal, fl, having a frequency of approximately 1 GHz.

4. The system of claim 1 wherein said first signal generator generates a first incident signal, f₁, and said second signal generator generates a second incident signal, f2, having a frequency close to but different than that of f₁.

5. The system of claim 1 wherein said first signal generator generates a first incident signal, f₁, having a frequency within the range of 10-24 GHz.

6. The system of claim 1 wherein said first signal generator generates a first incident signal, f₁, and said second signal generator generates a second incident signal, f2, having a frequency much lower than that of f₁.

7. The system of claim 1 wherein a second system, having its master clock synchronized to the master clock of the original system via a common timing mechanism, is used to provide antenna aperture enhancement such that the spatial resolution of the systems is increased.

8. The system of claim 1 in which a synthetic antenna aperture enhancement is achieved by operating the system at two different locations at a known time interval with respect to a manmade object.

10. The system of claim 1 further including audio output capabilities for notifying an operator of the results of the signal processor with respect to man-made objects.

11. The system of claim 1 further including a user interface for controlling the frequency of the transmitted waveforms.

12. The system of claim 1 in which the system is implemented into a fixed portal.

13. The system of claim 1 in which the system is implemented as a portable wearable unit that can be discreetly worn by an individual and used while the individual moves about an area.

14. The system of claim 1 in which the system is implemented as a portable unit that can be used while moving about an area.

9. The system of cairn 1 further including an operator display for displaying results of the signal processor with respect to man-made objects.

15. A method of detecting and characterizing man-made objects that possess nonlinear junctions, said method comprising:

transmitting, into free space, a first incident signal, f₁, and a second incident signal, f₂;

receiving reflected signals from man-made objects that possess nonlinear junctions as a result of said man-made objects being illuminated by said incident signals f₁ and f₂; and

processing said received reflected signals from said man-made objects that possess nonlinear junctions, such that the man-made objects can be characterized according to their composition.

16. The method of claim 15 wherein the received reflected signals include exact harmonic multiples of said transmitted signal f₁.

17. The method of claim 15 wherein the received reflected signals include inter-modulation products of said transmitted signals f₁ and f₂.

18. The method of claim 15 further comprising displaying the results of the processing step with respect to said man-made objects that possess nonlinear junctions.

19. The method of claim 15 in which said transmitting and receiving steps utilize an antenna assembly that is comprised of a high frequency directional array antenna, and a low frequency omni-directional array antenna.

20. The method of claim 15 in which said first incident signal, f₁, has a frequency of approximately 1 GHz.

21. The method of claim 15 in which said first incident signal, f₁, and said second incident signal, f2, have a frequencies close to but different from one another.

22. The method of claim 15 in which said first incident signal, f₁, has a frequency of within the range of 10-24 GHz.

23. The method of claim 15 in which said second incident signal, f2, has a frequency much less than said first incident signal, f₁.