Optically controlled RF MEMS switch array for reconfigurable broadband reflective antennas

• US 6,417,807 B1
• Filed: 04/27/2001
• Issued: 07/09/2002
• Est. Priority Date: 04/27/2001
• Status: Expired due to Term

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Hsu, Hui-Pin, Hsu, Tsung-Yuan
• Primary Examiner(s): Ho, Tan
• Application Number:
  US09/845,033
• Time in Patent Office: 438 Days
• Field of Search: 343/781.CA, 343/793, 343/795, 343/770, 343/876, 343/853, 333/107, 333/262, 200/181, 250/214.1, 250/214.LS
• US Class Current: 343/700.0MS
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 15/148 with means for varying the reflecting properties H01Q15/147 takes precedence
• CPC Class Codes: H01Q 3/247 by switching different parts of a primary active element
• CPC Class Codes: H01Q 9/14 Length of element or elements adjustable telescopic elements H01Q1/10
• CPC Class Codes: H01Q 9/285 Planar dipole H01Q9/065 takes precedence; patch antenna H01Q9/0407

Abstract

A method and apparatus for reconfiguring an antenna array by optical control of MEMS switches. A light source is provided to direct light to individual optically sensitive elements which control delivery of actuating bias voltage to the MEMS switches. The light source is preferably separated from the antenna array by a structure which conducts the controlling illumination but provides a high impedance electromagnetically reflective surface which reflects electromagnetic radiation over the antenna operating frequency range with small phase shift, and which is disposed very close to the antenna array. Optically sensitive elements preferably include photoresistive elements, which are best formed in the substrate upon which the MEM switches are formed, and may include photovoltaic elements.

Claims

1. A method for optically controlling an electromagnetic configuration of an antenna array element comprising the steps of:

providing a plurality of electrically-actuated mechanical switches for connecting sub-elements of the antenna array;

providing at least one optically sensitive electric control element to control actuation of at least one corresponding switch of the plurality of mechanical switches;

providing an optical transmission structure having regions which are optically transmissive from a first side of the optical transmission structure to a second side of the optical transmission structure;

disposing the antenna array element in a predetermined position on the first side of the optical transmission structure;

disposing a source of selectably controllable optical energy on the second side of the optical transmission structure;

selectively controlling the optical energy to illuminate a particular optically sensitive control element through a transmissive region of the optical transmission structure, thereby changing a position of a corresponding switch to change the configuration of the antenna array element.

2. The method of claim 1 wherein the optical transmission structure comprises a high-impedance electromagnetically reflective surface.

3. The method of claim 2 wherein the step of providing a transmission structure includes providing an insulator layer between said reflective surface and the antenna array element.

4. The method of claim 3 including the step of disposing the reflective surface less than one quarter wavelength of the antenna operating frequency away from the antenna array element.

5. The method of claim 1 including the step of providing a bias voltage to enable actuation of at least one of the mechanical switches to a first position.

6. The method of claim 5 wherein the step of providing a bias voltage includes conducting the bias voltage through the optical transmission structure.

7. The method of claim 5 wherein the step of providing a bias voltage includes the step of controlling the source of optical energy to illuminate a photovoltaic array.

8. The method of claim 5 wherein the step of providing an optically sensitive control element includes providing at least one photoresistive element, and including the further step of controlling the source of optical energy to illuminate the photoresistive element and thereby cause the mechanical switch to change to a second position.

9. The method of claim 8 wherein the step of providing the photoresistive element includes forming the photoresistive element in a substrate on which the switch is formed.

10. The method of claim 1 wherein said regions which are optically transmissive comprise tubes passing through the optical transmission structure to transmit optical energy to the optically sensitive control elements.

11. The method of claim 1 wherein the antenna array element is an element selected from the group consisting of dipole antenna elements, patch antenna elements, and slot antenna elements.

12. A reconfigurable antenna array comprising:

an array of antenna subelements;

a plurality of microelectromechanical system (MEMS) switches selectably connecting adjacent antenna subelements;

a plurality of optically sensitive elements, each optically sensitive element controlling a corresponding MEMS switch;

a matrix of optical power controlling elements selectably illuminating each optically sensitive element; and

an optical transmission layer, wherein the matrix of optical power controlling elements direct optical power to enter a transmissive region of the optical transmission layer on a first side thereof, and wherein the plurality of optically sensitive elements are on a second side of the optical transmission layer.

13. The reconfigurable antenna array of claim 12 including a bias voltage source for providing a bias voltage to actuate each of the MEMS switches into a first condition.

14. The reconfigurable antenna array of claim 13 wherein electrical resistance of an optically sensitive element of a selected MEM switch is lowered upon illumination to cause the selected MEM switch to actuate into a second condition.

15. The reconfigurable antenna array of claim 13 wherein the bias voltage source is a photovoltaic array illuminated under control of the matrix of optical power controlling elements.

16. The reconfigurable antenna array of claim 15 wherein the photovoltaic array is illuminated to actuate all the MEMS switches into a first condition.

17. The reconfigurable antenna array of claim 13 wherein the bias voltage source actuates all the MEMS switches into a first condition in an absence of illumination.

18. The reconfigurable antenna array of claim 17 wherein the reflective layer is located less than one quarter wavelength of an antenna operating frequency from the array of subelements.

19. The reconfigurable antenna array of claim 12, wherein said antenna array further comprises a substrate layer on which said plurality of MEMS switches and said array of subelements are disposed, and said optical transmission layer comprises:

a high-impedance electromagnetic reflective layer; and

an insulating material layer disposed between said subelements and said reflective layer.

20. The reconfigurable antenna array of claim 19 wherein the optically transmissive regions of the transmission layer include apertures through the optical transmission structure.

21. The reconfigurable antenna array of claim 20 wherein at least one of the apertures is electrically conductive and conducts a bias voltage to at least one of the MEM switches.

22. The reconfigurable antenna array of claim 20 wherein the optical transmission layer comprises a multilayer printed circuit board and the optical apertures are vias through the multilayer printed circuit board.

23. The reconfigurable antenna array of claim 12, wherein the array comprises one of a plurality of subarray modules.

24. The reconfigurable antenna array of claim 23, wherein the plurality of subarray modules are configured to provide the primary reflector of a Cassegrain antenna.

25. The reconfigurable antenna array of claim 12, wherein the antenna subelements is an antenna element selected from the group consisting of dipole antenna elements, patch antenna elements, and slot antenna elements.

26. A method for optically controlling an electromagnetic configuration of an antenna array element comprising the steps of:

providing a plurality of electrically-actuated mechanical switches for connecting sub-elements of the antenna array;

providing at least one optically sensitive electric control element to control actuation of at least one corresponding switch of the plurality of mechanical switches;

providing a high-impedance electromagnetically reflective structure having regions which are optically transmissive from a first side of the reflective structure to a second side of the reflective structure;

disposing the antenna array element in a predetermined position on the first side of the reflective structure;

disposing a source of selectably controllable optical energy on the second side of the reflective structure;

selectively controlling the optical energy to illuminate a particular optically sensitive control element through a transmissive region of the reflective structure, thereby changing a position of a corresponding switch to change the configuration of the antenna array element.

27. The method of claim 26 including the step of providing a bias voltage to enable actuation of at least one of the mechanical switches to a first position.

28. The method of claim 27 wherein the step of providing a bias voltage includes conducting the bias voltage through the reflective structure.

29. The method of claim 27 wherein the step of providing a bias voltage includes the step of controlling the source of optical energy to illuminate a photovoltaic array.

30. The method of claim 27 wherein the step of providing an optically sensitive control element includes providing at least one photoresistive element, and including the further step of controlling the source of optical energy to illuminate the photoresistive element and thereby cause the at least one mechanical switch to change to a second position.

31. The method of claim 30 wherein the step of providing the photoresistive element includes forming the photoresistive element in a substrate on which the at least one mechanical switch is formed.

32. The method of claim 26 wherein said regions which are optically transmissive comprise tubes passing through the reflective structure to transmit optical energy to the optically sensitive control elements.

33. The method of claim 26 wherein the step of providing a reflective structure includes providing an insulator layer between said reflective structure and the antenna array element.

34. The method of claim 33 including the step of disposing the reflective structure less than one quarter wavelength of the antenna operating frequency away from the antenna array element.

35. The method of claim 26 wherein the antenna array element is an element selected from the group consisting of dipole antenna elements, patch antenna elements, and slot antenna elements.

36. A reconfigurable antenna array comprising:

an array of antenna subelements;

a plurality of microelectromechanical system (MEMS) switches selectably connecting adjacent antenna subelements;

an optically sensitive element to selectably control each of the MEMS switches;

a matrix of optical power controlling elements to cause selective illumination of the optically sensitive element corresponding to each MEM switch so as to change an electromagnetic configuration of the antenna array; and

a high impedance electromagnetically reflective layer, wherein the matrix of optical power controlling elements control optical power to enter a transmissive region of the reflective layer on a first side thereof, and wherein the optically sensitive elements are on a second side of the reflective layer.

37. The reconfigurable antenna array of claim 36 including a bias voltage source for providing a bias voltage to actuate each of the MEMS switches into a first condition.

38. The reconfigurable antenna array of claim 37 wherein electrical resistance of an optically sensitive element of a selected MEM switch is lowered upon illumination to cause the selected MEM switch to actuate into a second condition.

39. The reconfigurable antenna array of claim 37 wherein the bias voltage source is a photovoltaic array illuminated under control of the matrix of optical power controlling elements.

40. The reconfigurable antenna array of claim 39 wherein the photovoltaic array is illuminated to actuate all the MEMS switches into a first condition.

41. The reconfigurable antenna array of claim 37 wherein the bias voltage source actuates all the MEMS switches into a first condition in an absence of illumination.

42. The reconfigurable antenna array of claim 36, wherein the antenna array further comprises:

a substrate layer on which the plurality of MEMS switches and the array of subelements are disposed; and

an insulating material layer disposed between the antenna subelements and the reflective layer.

43. The reconfigurable antenna array of claim 42 wherein the optically transmissive regions of the reflective layer include apertures through the optical transmission structure.

44. The reconfigurable antenna array of claim 43 wherein at least one of the apertures is electrically conductive and conducts a bias voltage to at least one of the MEM switches.

45. The reconfigurable antenna array of claim 44 wherein the reflective layer comprises a multilayer printed circuit board and the optical apertures are vias through the multilayer printed circuit board.

46. The reconfigurable antenna array of claim 36 wherein the reflective layer is located less than one quarter wavelength of an antenna operating frequency from the array of subelements.

47. The reconfigurable antenna array of claim 36, wherein the array comprises one of a plurality of subarray modules.

48. The reconfigurable antenna array of claim 47, wherein the plurality of subarray modules are configured to provide the primary reflector of a Cassegrain antenna.

49. The reconfigurable antenna array of claim 36, wherein at least one of the antenna subelements is an antenna element selected from the group consisting of dipole antenna elements, patch antenna elements, and slot antenna elements.