Tunable micro electromechanical inductor

• US 7,741,936 B1
• Filed: 09/04/2007
• Issued: 06/22/2010
• Est. Priority Date: 09/09/2004
• Status: Active Grant

• Current Assignee: University of South Florida (State University System of Florida)
• Original Assignee: University of South Florida (State University System of Florida)
• Inventors: Balachandran, Srinath, Weller, Thomas, Lakshminarayanan, Balaji
• Primary Examiner(s): Takaoka; Dean O
• Application Number:
  US11/849,703
• Time in Patent Office: 1,022 Days
• Field of Search: 333/101, 333/105, 333/262, 200/181
• US Class Current: 333/262
• CPC Class Codes: H01F 2017/0046 with a conductive path having a bridge
• CPC Class Codes: H01F 21/04 by relative movement of turns or parts of windings
• CPC Class Codes: H01P 1/127 Strip line switches
• CPC Class Codes: H01P 3/003 Coplanar lines
• CPC Class Codes: H01P 5/04 with variable factor of coupling

Abstract

The present invention provides a monolithic inductor developed using radio frequency micro electromechanical (RF MEMS) techniques. In a particular embodiment of the present invention, a tunable radio frequency microelectromechanical inductor includes a coplanar waveguide and a direct current actuatable contact switch positioned to vary the effective width of a narrow inductive section of the center conductor of the CPW line upon actuation the DC contact switch. In a specific embodiment of the present invention, the direct current actuatable contact switch is a diamond air-bridge integrated on an alumina substrate to realize an RF switch in the CPW and microstrip topology.

Claims

1. A tunable radio frequency microelectromechanical inductor, the inductor comprising:

a coplanar waveguide having a center conductor and two spaced apart ground conductors, the center conductor positioned between the two spaced apart ground conductors, and the center conductor further comprising a narrow width inductive section;

at least one direct current actuatable diamond micro-bridge contact switch positioned to vary the effective width of the narrow inductive section of the center conductor upon actuation of the at least one contact switch; and

a direct current bias line positioned to actuate the at least one actuatable diamond micro-bridge contact switch.

2. The tunable inductor of claim 1, wherein the inductive section of the center conductor is substantially straight and of uniform width over the length of the section.

3. The tunable inductor of claim 1, wherein the inductive section of the center conductor is a meandered center conductor over the length of the section.

4. The tunable inductor of claim 1, wherein the actuatable contact switch is in contact at one end with the center conductor and suspended above the coplanar waveguide bordering the narrow inductive section of the center conductor.

5. The tunable inductor of claim 1, wherein the actuatable contact switch is a boron-doped diamond micro-bridge having deposited bi-metal copper lines.

6. The tunable inductor of claim 1, wherein the diamond micro-bridge is about 1200 μ

m long and 300 μ

m wide.

7. The tunable inductor of claim 1, wherein the diamond micro-bridge is thermally actuatable using a bi-metal actuation scheme.

8. The tunable inductor of claim 1, wherein the direct current bias line passes through a cut in the ground plane of the ground conductors and under the actuatable switch.

9. The tunable inductor of claim 1, wherein the direct current bias line is a SiCr line passing through a cut in the ground plane of the ground conductors and the ground planes split by the cut are electrically connected through a thin wire-bond.

10. The tunable inductor of claim 1, wherein the direct current bias line is a SiCr line passing through a cut in the ground plane of the ground conductors and the ground planes split by the cut are electrically connected through an air-bridge.

11. The tunable inductor of claim 1, wherein the at least one direct current actuatable diamond micro-bridge contact switch further comprises a plurality of direct current actuatable diamond micro-bridge contact switches.

12. The tunable inductor of claim 1, wherein the length of the narrow width inductive section of the center conductor is equal to approximately one fourth of an operating wavelength of the inductor.

13. The tunable inductor of claim 1, wherein the length of the inductive section is approximately 600 μ

m.

14. A method of tuning a radio frequency microelectromechanical inductor, the method comprising the steps of:

providing a coplanar waveguide having a center conductor and two spaced apart ground conductors, the center conductor positioned between the two spaced apart ground conductors, and the center conductor further comprising a narrow width inductive section;

positioning at least one direct current actuatable diamond micro-bridge contact switch to vary the effective width of the narrow inductive section of the center conductor upon actuation of the at least one contact switch; and

positioning a direct current bias line to actuate the at least one actuatable diamond micro-bridge contact switch.

15. A tunable radio frequency microelectromechanical inductor, the inductor comprising:

a coplanar waveguide having a center conductor and two spaced apart ground conductors, the center conductor positioned between the two spaced apart ground conductors, and the center conductor further comprising a narrow width inductive section;

two diamond micro-bridges positioned on opposite sides of the narrow inductive width section and spanning the narrow width induction section, the diamond micro-bridges positioned to vary the effective width of the narrow inductive section of the center conductor upon actuation of the two diamond micro-bridges; and

a direct current bias line positioned to actuate the two diamond micro-bridges, the bias line passing through a cut in the ground plane of the ground conductors and the ground planes split by the cut being electrically connected through a thin wire-bond.