Assembly having variable capacitance

• US 6,700,299 B2
• Filed: 03/31/2003
• Issued: 03/02/2004
• Est. Priority Date: 08/09/2000
• Status: Expired due to Term

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Wenk, Beatrice, Quenzer, Hans-Joachim, Wagner, Bernd
• Primary Examiner(s): Ponomarenko, Nicholas
• Assistant Examiner(s): Mohandesi, Iraj A.
• Application Number:
  US10/343,975
• Publication Number:
  US 20040012299A1
• Time in Patent Office: 337 Days
• Field of Search: 310/311, 310/309
• US Class Current: 310/311
• CPC Class Codes: H01G 5/14 due to longitudinal movement of electrodes
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping

Abstract

The present invention relates to an assembly of variable capacitance as well as to a method of operating the assembly. In the assembly, a variable capacitor is formed by a variable coverage or a variable distance of at least one first (4) and one second electrically conductive region (5). The first electrically conductive region (4) is configured on or in a substrate (1) and said second electrically conductive region (5) is configured on or in an actuator element (3) of a first micro-mechanical actuator (2). The actuator (2) is disposed on the substrate (1) in such a way that it can perform a movement of the actuator element (3) with the second region (5) along a surface of the substrate (1) at different positions relative to the first region (4), at which positions the second region (5) overlaps the first region (4) at least partly. Moreover, holding means (6, 10, 11) are provided which are capable of pulling or pushing the actuator element (3) in the different positions towards the substrate (1) or a mechanical stop (13) on the substrate (1), and of holding it in these positions.

The inventive assembly serves to implement a variable capacitance that presents a high stability in resistance to outside influences according to its respective setting.

Claims

1. Assembly of variable capacitance comprising a variable coverage or a variable distance of at least one first electrically conductive area and at least one second electrically conductive area, with said at least one first electrically conductive area being configured on or in a substrate and with said at least one second electrically conductive area being on or in an actuator element of a first micro-mechanical actuator that is disposed on said substrate in such a way that said first micro-mechanical actuator is capable of performing, by means of a first drive system, movement of said actuator element with said at least one second electrically conductive area along a surface of said substrate at different positions relative to said at least one first electrically conductive area at which positions said at least one second electrically conductive area overlaps said at least one first electrically conductive area at least partly;

and holding means capable, by means of a second drive system independent of said first drive system, of pulling or pushing said actuator element in said different positions towards said substrate or a mechanical stop on said substrate and of holding said actuator element in such positions.

2. Assembly according to claim 1, wherein said holding means includes at least one third electrically conductive area on or in said substrate and at least one fourth electrically conductive area on or in said actuator element that overlap each other in the different positions of said actuator element at least partly and are capable of being subjected to a difference in electrical voltage.

3. Assembly according to claim 1, wherein said holding means includes a second micro-mechanical actuator.

4. Assembly according to claim 3, wherein said second micro-mechanical actuator is a thermo-mechanical actuator that is so configured and disposed relative to said first micro-mechanical actuator that said second micro-mechanical actuator is deflected in a direction substantially orthogonal on the surface of said substrate in response to thermal excitation and that a first section of said actuator element of said first micro-mechanical actuator in the different positions reaches up to a zone underneath a second section of said second micro-mechanical actuator in a deflected state.

5. Assembly according to claim 4, wherein said second mirco-mechanical actuator includes one or several beam-shaped elements that are clamped on both sides of said substrate.

6. Assembly according to claim 4 wherein, said first section of said actuator element of said first micro-mechanical actuator is a plate-like cantilever arm that extends along a direction of movement of said actuator element.

7. Assembly according to claim 4, wherein said second section of said second micro-mechanical actuator is a plate-like cantilever arm that extends in a direction opposite to a direction of movement of said actuator element of said first micro-mechanical actuator.

8. Assembly according to claim 4, wherein said first section and said second section are constructed and arranged such that they engage each other when the thermal excitation of said second micro-mechanical actuator is terminated while said actuator element of said first micro-mechanical actuator is in said different positions.

9. Assembly according to claim 1, wherein said first micro-mechanical actuator is an electrostatic micro actuator.

10. Assembly according to claim 9, wherein said first micro-mechanical actuator comprises a drive system with parallel-plate capacitors in a comb-like arrangement.

11. Assembly according to claim 9, wherein said actuator element comprises bending joints to enlarge a stroke of movement that can be achieved with said first micro-mechanical actuator.

12. Assembly according to claim 1, wherein said first micro-mechanical actuator is a thermo-mechanical micro actuator.

13. Assembly according to claim 12, wherein said first micro-mechanical actuator includes one or several beam-shaped elements that are clamped on both sides of said substrate.

14. Assembly according to claim 1, wherein said at least one first electrically conductive area and said at least one second electrically conductive area are plate-like areas or elements.

15. Assembly according to claim 1, wherein electrical leads to said at least one first electrically conductive area and said at least one second electrically conductive area are micro strip-type lines and that a protective cover for said micro-mechanical actuator on said substrate comprises a metal coating on its inner surface.

16. Assembly according to claim 1 further comprising invariable capacitors configured on said substrate, which are adapted to be switched separately via switching elements parallel with said variable capacitor formed by said at least one first electrically conductive area and said at least one second electrically conductive area.

17. Assembly according to one of claims 1 to 16, wherein one or more of said assembly are present and are connected in parallel.

18. Method of setting a predeterminable capacitance by means of an assembly according to one of claims 1 to 16, wherein said actuator element of said first micro-mechanical actuator is moved to a position in which said at least one second electrically conductive area presents a spacing from and an at least partial coverage with said at least one first electrically conductive area, which correspond to said predeterminable capacitance, and said holding means are controlled for holding at this position.

19. Method according to claim 18, wherein a respective actual position of said actuator element is detected by a measurement of a reference capacitance between one or several regions provided on said actuator element and on said substrate.

20. Method according to claim 18, wherein said first micro-mechanical actuator is operated at its resonance frequency.