Microwave and millimeter wave imaging system

• US 7,746,266 B2
• Filed: 03/20/2008
• Issued: 06/29/2010
• Est. Priority Date: 03/20/2008
• Status: Active Grant

• Current Assignee: Curators of the University of Missouri (University of Missouri)
• Original Assignee: Curators of the University of Missouri (University of Missouri)
• Inventors: Pommerenke, David, Ghasr, Mohammad Tayeb Ahmad, Zoughi, Reza, Kharkivskiy, Sergiy, AbouKhousa, Mohamed Ahmed
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Barker; Matthew M
• Application Number:
  US12/052,589
• Publication Number:
  US 20090237092A1
• Time in Patent Office: 831 Days
• Field of Search: 342/22
• US Class Current: 342/22
• CPC Class Codes: G01R 29/0878 Sensors; antennas; probes; detectors wave guide measuring sections G01R1/24
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 7/025 involving the transmission of linearly polarised waves
• CPC Class Codes: G01S 7/032 Constructional details for solid-state radar subsystems
• CPC Class Codes: H01Q 21/064 using horn or slot aerials slotted waveguides arrays H01Q21/005
• CPC Class Codes: H01Q 3/46 Active lenses or reflecting arrays

Abstract

A sensor array having a plurality of modulated slots for microwave and/or millimeter wave imaging. The locations of the slots in the array define a spatial domain away from an object for detecting an electric field from the object. Each of the slots outputs a signal representative of the measured field and the location of the slot. A processor decodes the signals and generates an image of the object.

Claims

1. An imaging system comprising:

a conductive surface having a plurality of slots formed therein at locations corresponding to a defined spatial domain located remotely from an object;

a plurality of active elements for modulating the slots, wherein each of the slots has at least one of the active elements connected thereacross for selectively modulating the slot, wherein the modulated slots comprise a sensor array for measuring an electric field from the object, and wherein each of the modulated slots provides an output signal representative of the electric field detected at the respective location of the modulated slot, and wherein the at least one of the active elements connected across each of the slots selectively changes the resonant frequency thereof;

a receiver operatively connected to the array for receiving the output signals from the modulated slots;

a processor configured to generate a multi-dimensional profile representative of the object in the defined spatial domain based on the received output signals from the modulated slots; and

a display for displaying an image of the multi-dimensional profile.

2. The imaging system of claim 1, wherein the active elements each comprise a PIN diode electrically connected to the respective slot, and wherein the output signal of each of the modulated slots is representative of a phase and magnitude of the electric field detected at the respective location of the modulated slot.

3. The imaging system of claim 1, wherein each of the slots is linearly polarized.

4. The imaging system of claim 1, wherein the slots comprise one or more of the following types:

sub-resonant, resonant, wide-band, reconfigurable resonant, and shape reconfigurable.

5. The imaging system of claim 1, wherein the sensor array is responsive to millimeter wave or microwave electromagnetic energy.

6. The imaging system of claim 1, wherein the sensor array is adjustable for measuring the electric field at different polarizations.

7. The imaging system of claim 1, wherein the sensors are dual-polarized sensor elements with electrical control over the polarization for measuring two orthogonal electric field components.

8. The imaging system of claim 1, wherein the sensor array samples the electric field from the object at the plurality of slots, and wherein the sensor array is movable in at least two orthogonal directions to increase image resolution by increasing a number of samples obtained per image.

9. The imaging system of claim 1, wherein the array is movable relative to the object.

10. The imaging system of claim 1, wherein the multi-dimensional profile comprises an image of the object in view.

11. The imaging system of claim 1, wherein the output signal of each of the slots has a unique identity corresponding to the respective location thereof in the sensor array, and wherein the processor is configured to generate a map of the measured electric field based on the unique identity of each of the output signals.

12. The imaging system of claim 1, wherein the receiver comprises a rectangular waveguide positioned behind the sensor array and having a resonant slot at its aperture for receiving one or more signals output from the slots.

13. The imaging system of claim 1, wherein the receiver comprises a pickup network of combiners/dividers and microstrip/strip lines manufactured on a printed circuit board.

14. The imaging system of claim 1, wherein the receiver comprises the modulated slots cut into a wall of a metallic/dielectric waveguide section.

15. The imaging system of claim 1, further comprising an electric field source for illuminating the object, said electric field comprising electromagnetic energy having a frequency greater than ultra high frequency and being scattered by the object illuminated thereby.

16. An imaging system comprising:

a plurality of modulated slots formed in a conductive surface at a plurality of locations, said locations corresponding to a defined spatial domain located remotely from an object, said modulated slots receiving and responsive to electromagnetic energy at a frequency greater than ultra high frequency for detecting an electric field from the object, said modulated slots each having an active element connected thereacross for selectively changing the resonant frequency thereof to modulate the modulated slot and providing an output signal representative of the electric field detected at the respective location of the modulated slot as a function of the resonant frequency thereof;

a receiver operatively connected to the modulated slots for receiving the output signals representative of the electric field detected at the plurality of locations; and

a processor configured to generate a multi-dimensional profile representative of the object in the defined spatial domain based on the received output signals from the modulated slots.

17. The imaging system of claim 16, wherein the active element comprises a PIN diode electrically connected to the respective slot at a location of maximum electric field strength, and wherein the output signal of each of the modulated slots is representative of a phase and magnitude of the electric field detected at the respective location of the modulated slot.

18. The imaging system of claim 16, wherein each of the slots is linearly polarized.

19. The imaging system of claim 16, wherein the slots comprise one or more of the following resonant modulation types:

sub-resonant, resonant, wide-band, reconfigurable resonant, and shape reconfigurable.

20. The imaging system of claim 16 wherein the electric field comprises microwave or millimeter wave electromagnetic energy.

21. The imaging system of claim 16, wherein the receiver comprises a rectangular waveguide having a resonant slot at its aperture for receiving one or more signals output from the slots.

22. The imaging system of claim 17, wherein the receiver comprises a pickup network of combiners/dividers and microstrip lines manufactured on a printed circuit board.

23. The imaging system of claim 16, wherein the conductive surface comprises a waveguide having the slots formed therein.

24. The imaging system of claim 16, further comprising a display operatively connected to the processor for displaying an image of the multi-dimensional profile generated thereby.

25. The imaging system of claim 16, wherein the plurality of slots formed in the conductive surface comprise a sensor array, said sensor array being adjustable for measuring the scattered electric field at different polarizations.

26. The imaging system of claim 16, wherein the plurality of slots sample the electric field from the object, and wherein the conductive surface is movable in at least two orthogonal directions to increase image resolution by increasing a number of samples obtained from each of the slots.

27. A method of generating a multi-dimensional profile of an object, said method comprising:

illuminating the object with an electric field, said electric field comprising electromagnetic energy having a frequency greater than ultra high frequency and being scattered by the object illuminated thereby;

sampling the scattered electric field at a plurality of locations via a sensor array, said locations corresponding to a defined spatial domain located remotely from the object, said array including a modulated slot at each of the locations for detecting the scattered electric field, said modulated slot comprising an active element connected thereto for modulating the slot, said modulated slots each providing an output signal representative of the electric field detected at the respective location of the modulated slot, wherein the modulating comprises modulating each of the slots in the sensor array by selectively changing the resonant frequency thereof;

receiving the output signals from the modulated slots; and

generating a multi-dimensional profile representative of the object in the defined spatial domain based on the received output signals from the modulated slots of the sensor array.

28. The method of claim 27, further comprising displaying an image of the multi-dimensional profile.

29. The method of claim 27, further comprising linearly polarizing each of the slots.

30. The method of claim 27, further comprising adjusting the sensor array for measuring the scattered electric field at different polarizations.

31. The method of claim 30, wherein adjusting the sensor array comprises rotating the array about a central point.

32. The method of claim 27, wherein sampling the electric field comprises moving the sensor array to increase image resolution by increasing a number of samples obtained from each of the slots.

33. The method of claim 32, wherein moving the sensor array comprises translationally displacing the sensor array in one or more orthogonal directions.

34. The method of claim 27, wherein sampling the electric field comprises moving the sensor array relative to the object to scan the scattered electric field.

35. The method of claim 27, further comprising loading each of the slots via the active element electrically connected thereto.

36. The method of claim 27, wherein receiving the output signals from the slots comprises positioning a rectangular waveguide behind the sensor array, said waveguide having a slot at its aperture for receiving one or more signals output from the slots.

37. The method of claim 27, wherein receiving the output signals from the slots comprises receiving one or more signals output from the slots at a pickup network of combiners/dividers and microstrip/strip lines.