Electronically reconfigurable microwave lens and shutter using cascaded frequency selective surfaces and polyimide macro-electro-mechanical systems

• US 6,822,622 B2
• Filed: 07/29/2002
• Issued: 11/23/2004
• Est. Priority Date: 07/29/2002
• Status: Active Grant

• Current Assignee: Ball Aerospace & Technologies Corporation (Ball Corporation)
• Original Assignee: Ball Aerospace & Technologies Corporation (Ball Corporation)
• Inventors: Crawford, Thomas M., Lalezari, Farzin, Boone, Theresa C., Kelly, P. Keith
• Primary Examiner(s): Nguyen, Hoang V.
• Application Number:
  US10/208,507
• Publication Number:
  US 20040017331A1
• Time in Patent Office: 848 Days
• Field of Search: 343/909, 343/753, 343/754, 343/756, 343/767, 343/770, 343/700.MS
• US Class Current: 343/909
• CPC Class Codes: H01Q 15/002 said selective devices being reconfigurable or tunable, e.g. using switches or diodes
• CPC Class Codes: H01Q 3/44 varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element

Abstract

A radio frequency reconfigurable lens is provided. In particular, a lens comprising at least two opposed frequency selective surface sheets is provided. A relative phase shift may be imparted to an incident radio frequency wave by varying the distance between at least some of the unit cells of a first of the FSS sheets and adjacent unit cells on a second of the FSS sheets. In order to provide a desired phase taper across the width of a lens, and/or to provide different phase shift amounts, pairs of FSS surfaces having controllable columns or rows can be cascaded together. According to an additional aspect of the present invention, radio frequency waves can be scanned by cascading multiple tunable stages. The present invention also provides a radio frequency shutter.

Claims

1. An antenna apparatus, comprising:

a first frequency selective surface; and

a second frequency selective surface interconnected to said first frequency selective surface such that at least a first portion of said second frequency selective surface overlaps at least a first portion of said first frequency selective surface and such that a distance of said at least a first portion of said second frequency selective surface from said at least a first portion of said first frequency selective surface can be selectively altered,

wherein in a first mode said at least a first portion of said second frequency selective surface is a first distance from said at least a first portion of said first frequency selective surface to present a first admittance to a signal having a first frequency, and

wherein in a second mode said at least a first portion of said second frequency selective surface is a second distance from said at least a first portion of said frequency selective surface to present a second admittance to said signal having a first frequency.

2. The antenna apparatus of claim 1, wherein a second portion of said first frequency selective surface overlaps a second portion of said second frequency selective surface,

wherein in a third mode said second portion of said first frequency selective surface is said first distance from said second portion of said second frequency selective surface to present said first admittance to said signal having a first frequency, and

wherein in a fourth mode said second portion of said first frequency selective surface is a third distance from said second portion of said second frequency selective surface to present a third admittance to said signal having a first frequency.

3. The antenna apparatus of claim 1, wherein said first frequency selective surface comprises an array of unit cells, and wherein said second frequency selective surface comprises an array of unit cells.

4. The antenna apparatus of claim 3, wherein at least a majority of said unit cells of said first frequency selective surface have a unit cell size that is different from a unit cell size of at least a majority of said second frequency selective surface.

5. The antenna apparatus of claim 3, wherein said first frequency selective surface is registered with said second frequency selective surface such that at least a first edge of a unit cell of said first frequency selective surface is not aligned with at least a first edge of a unit cell of said second frequency selective surface.

6. The antenna apparatus of claim 3, wherein said unit cells of said first frequency selective surface comprise resonant slots.

7. The antenna apparatus of claim 1, wherein said first and second frequency selective surfaces comprise a flexible substrate coupled to an electrically conductive layer, and wherein resonant slots are formed in said conductive layer.

8. The antenna apparatus of claim 1, further comprising a voltage source, wherein in said second mode of operation a non-zero voltage potential is established between said at least a first portion of said first frequency selective surface and said at least a first portion of said second frequency selective surface.

9. The antenna apparatus of claim 1, further comprising:

a third frequency selective surface;

a fourth frequency selective surface interconnected to said third frequency selective surface such that at least a first portion of said fourth frequency selective surface overlaps at least a first portion of said third frequency selective surface and such that a distance of said at least a first portion of said fourth frequency selective surface from said at least a first portion of said third frequency selective surface can be selectively altered,

wherein in a third mode said at least a first portion of said fourth frequency selective surface is a third distance from said at least a first portion of said third frequency selective surface to present a third admittance to a signal having a first frequency,

wherein in a fourth mode said at least a first portion of said fourth frequency selective surface is a fourth distance from said first portion of said third frequency selective surface to present a fourth admittance to said signal having a first frequency,

wherein said first and second frequency selective surfaces comprise a first phase shifter,

wherein said third and fourth frequency selective surfaces comprise a second phase shifter,

wherein said first and second phase shifters are positioned such that at least a portion of said first phase shifter overlaps at least a portion of said second phase shifter.

10. The antenna apparatus of claim 1, wherein in said first mode of operation said frequency selective surfaces are tuned to present a low transmission loss to said signal having a first frequency, and wherein in said second mode of operation said frequency selective surfaces are de-tuned to present a high transmission loss to said signal having a first frequency.

11. A method of shifting the phase of a radio frequency signal, comprising:

generating a radio frequency signal;

positioning a first frequency selective surface in a path of said radio frequency signal;

positioning a second frequency selective surface in a path of said radio frequency signal;

positioning at least a first portion of said second frequency selective surface a first distance from at least a first portion of said first frequency selective surface to phase shift at least a first portion of said radio frequency signal by a first amount; and

positioning said at least a first portion of said second frequency selective surface a second distance from said at least a first portion of said first frequency selective surface to phase shift said at least a first portion of said radio frequency signal by a second amount.

12. The method of claim 11, wherein said step of positioning said at least a first portion of said second frequency selective surface a first distance from said first frequency selective surface to phase shift said radio frequency signal by a first amount comprises introducing a first voltage potential between said at least a first portion of said first frequency selective surface and said at least a first portion of said second frequency selective surface, and

wherein said step of positioning said at least a first portion of said second frequency selective surface a second distance from said at least a first portion of said first frequency selective surface to phase shift said radio frequency signal by a second amount comprises introducing a second voltage potential between said at least a first portion of said first frequency selective surface and said at least a first portion of said second frequency selective surface.

13. The method of claim 11, wherein said first and second frequency selective surfaces comprise arrays of unit cells, and wherein said at least a first portion of said first frequency selective surface comprises at least a first column of unit cells.

14. The method of claim 13, wherein at least a first edge of each of said unit cells of said first frequency selective surface are not aligned with at least a first edge of a corresponding one of said unit cells of said second frequency selective surface.

15. The method of claim 14, wherein at least a majority of said unit cells of said first frequency selective surface have a unit cell size that is different from a unit cell size of at least a majority of said unit cells of said second frequency selective surface.

16. The method of claim 11, wherein said step of positioning said at least a first portion of said second frequency selective surface a second distance from said at least a first portion of said first frequency selective surface comprises positioning substantially all of said second frequency selective surface a second distance from said first frequency selective surface, wherein said frequency selective surfaces are de-tuned to form a closed shutter with respect to said radio frequency signal.

17. A radio frequency lens, comprising:

a first frequency selective surface, comprising;

an array of unit cells;

a second frequency selective surface, comprising;

an array of unit cells, wherein said first and second frequency selective surfaces are registered with respect to one another such that at least a first edge of at least a first unit cell of said first frequency selective surface is not aligned with at least a first edge of at least a first unit cell of said second frequency selective surface, wherein said first frequency selective surface and said second frequency selective surface are a first distance from one another when said lens is in a first mode of operation, and wherein at least a portion of said second frequency selective surface is movable with respect to at least a first portion of said first frequency selective surface to position said at least a first portion of said second frequency selective surface a second distance from said at least a first portion of said first frequency selective surface when said lens is in a second mode of operation.

18. The radio frequency lens of claim 17, wherein at least a majority of said unit cells of said first frequency selective surface have a unit cell size that is different from a unit cell size of at least a majority of said unit cells of second frequency selective surface.

19. The radio frequency lens of claim 17, further comprising a voltage source, wherein in said first mode of operation a first potential difference between said at least a first portion of said first frequency selective surface and said at least a first portion of said second frequency selective surface is established, and wherein in a second mode of operation a second potential difference is established between said at least a first portion of said first frequency selective surface and said at least a first portion of said second frequency selective surface.

20. The radio frequency lens of claim 17, wherein said second frequency selective surface further comprises:

a flexible substrate; and

an electrically conductive layer, interconnected to said flexible substrate, wherein said unit cells are defined by slots formed in said conductive layer.

21. The radio frequency lens of claim 17, wherein said first portion of said first frequency selective surface is defined by electrically insulating a first column of unit cells from a second portion of said first frequency selective surface.

22. The radio frequency lens of claim 17, wherein in said second mode of operation radio frequency radiation having at least a first frequency propagating through said lens experiences a transmission loss that is greater than a transmission loss experienced by said radio frequency radiation when said radio frequency lens is in said first mode of operation.

23. The radio frequency lens of claim 22, wherein said radio frequency lens functions as an open shutter in said first mode of operation and a closed shutter in said second mode of operation.

24. A method of steering a radio frequency beam, comprising:

providing a first array of unit cells;

providing a second array of unit cells;

registering said first array with respect to said second array, wherein at least a first edge of a one of said unit cells of said first array is not aligned with at least a first edge of a corresponding one of said unit cells of said second array;

separating said first and second arrays by a first amount, wherein a first phase shifter is formed, and wherein a first radio frequency signal incident on said first and second arrays is phase shifted a first amount; and

separating at least a portion of said first array from at least a portion of said second array by a second amount, wherein said first radio frequency signal incident on said at least a portion of said first array and at least a portion of said second array separated by said second amount is phase shifted a second amount.

25. The antenna apparatus of claim 24, wherein at least a majority of said unit cells of said first array have a unit cell size that is different from a unit cell size of at least a majority of said unit cells of said second array.

26. The method of claim 24, wherein said unit cells of said first array are divided into columns of unit cells, and wherein a first column of said unit cells is not electrically interconnected to a second column of said unit cells.

27. The method of claim 24, wherein said first array of unit cells comprises:

a dielectric substrate; and

an electrically conductive layer, wherein said electrically conductive layer is patterned to define said unit cells.

28. The method of claim 27, wherein said unit cells are defined by slots formed in said electrically conductive layer.

29. The method of claim 27, wherein said dielectric substrate is flexible.

30. The method of claim 24, wherein said first array and said second array are substantially planar.

31. The method of claim 24, wherein said separation between said at least a portion of said first array and said at least a portion of said second array by said second amount is achieved by introducing an attractive force between said at least a portion of said first array and said at least a portion of said second array.

32. The method of claim 31, wherein said attractive force comprises an electrostatic force.

33. The method of claim 31, wherein said attractive force acts in opposition to a spring force tending to maintain said separation between said first array and said second array in said first amount.

34. The method of claim 33, wherein said separation between said first array and said second array by said first amount is achieved by removing an attractive force between said at least a portion of said first array and said at least a portion of said second array.

35. The method of claim 24, wherein an admittance produced by said at least a portion of said first array and said at least a portion second array with respect to said incident signal is altered when said portions are separated by a second amount as compared to when said portions are separated by a first amount.

36. The method of claim 24, further comprising:

providing a third array of unit cells;

providing a fourth array of unit cells;

registering said third array with respect to said fourth array, wherein at least a first edge of a one of said unit cells of said third array is not aligned with at least a first edge of a one of said unit cells of said fourth array;

separating said third and fourth arrays by a third amount, wherein a second phase shifter is formed;

separating at least a portion of said third array from at least a portion of said fourth array by a fourth amount; and

registering said first phase shifter with respect to said second phase shifter, wherein said first radio frequency signal, incident on said first and second phase shifters, is phase shifted a third amount when said third and fourth arrays of said second phase shifter are separated by said third amount, and wherein said radio frequency signal incident on said at least a portion of said third array and at least a portion of said fourth array is phase shifted by a fourth amount when said at least a portion of said third array and said at least a portion of said fourth array are separated by said fourth amount.

37. The method of claim 36, wherein a portion of said first radio frequency signal incident on said at least a portion of said first array and said at least a portion of said second array separated by said second amount and incident on said at least a portion of said third array and said at least a portion of said fourth array separated by said fourth amount is phase shifted a fifth amount.

38. The method of claim 36, wherein said unit cells of said first array are divided into columns of unit cells, and wherein a first column of said unit cells is not electrically interconnected to a second column of said unit cells, and wherein said unit cells of said third array are divided into rows of unit cells, wherein a first row of said unit cells is not electrically interconnected to a second row of said unit cells, wherein said radio frequency signal incident on said at least a portion of said first array and said at least a portion of said second array and incident on said at least a portion of said third array and said at least a portion of said fourth array may be scanned in two dimensions.

39. The method of claim 36, further comprising interposing a spacer between said first and second phase shifters, whereby a first spacing is maintained between said first and said second phase shifters.

40. A tunable device for steering radio frequency signals, comprising:

a first tunable stage operable to selectively phase shift an incident radio frequency signal having a first frequency by a first amount in a first mode of operation and by a second amount in a second mode of operation;

a second tunable stage operable to selectively phase shift an incident radio frequency signal having a first frequency by a third amount in a first mode of operation and by a fourth amount in a second mode of operation, wherein said second tunable stage at least substantially overlaps said first tunable stage, wherein an incident radio frequency signal can be steered by selectively controlling said modes of operation of said first and second tunable stages.

41. The device of claim 40, wherein said first tunable stage comprises a plurality of diodes for controlling an index of refraction of said lens.

42. The device of claim 40, wherein said first tunable stage comprises a ferroelectric material having a first radio frequency resonance in said first mode of operation and a second radio frequency resonance in said second mode of operation.