RF MEMS switch

• US 6,426,687 B1
• Filed: 05/22/2001
• Issued: 07/30/2002
• Est. Priority Date: 05/22/2001
• Status: Expired due to Term

• Current Assignee: Aerospace Corporation
• Original Assignee: Aerospace Corporation
• Inventors: Osborn, Jon Victor
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): TAKAOKA, DEAN O
• Application Number:
  US09/862,954
• Time in Patent Office: 434 Days
• Field of Search: 333/262, 333/105, 333/258, 200/181
• US Class Current: 333/262
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes
• CPC Class Codes: H01G 5/38 Multiple capacitors, e.g. ganged
• CPC Class Codes: H01G 5/40 Structural combinations of variable capacitors with other electric elements not covered by this subclass, the structure mainly consisting of a capacitor, e.g. RC combinations
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H01P 1/127 Strip line switches

Abstract

A radio frequency (RF) microelectromechanical systems (MEMS) switch is manufactured by independent processing and subsequent bonding together of a MEMS substrate in alignment with an RF substrate. The RF MEMS switch is designed so as to encapsulate a flexing diaphragm supporting a switch electrode used with electrostatic flexing potentials to move electrodes of the MEMS substrate up and down over an RF transmission line structure of the RF substrate. The bonded combined MEMS switch structure is used to create an encapsulated RF MEMS switch suitable for direct coupling, AC coupling, and direct modulation of RF signals. The resulting MEMS RF switch device provides a reliable, minimally distorting RF transmission line geometry, free of contamination for use in high speed RF signal switching applications well suited for advance communication RF switching requirements.

Claims

1. A switch comprising,

a MEMS substrate,

a diaphragm suspended from and attached to the substrate, the diaphragm being suspended equilaterally from the MEMS substrate,

a bridge disposed on the diaphragm, the diaphragm being flexible to move the bridge up and down,

a plurality of equilaterally displaced electrodes surrounding the bridge, the electrodes are controlled by controlling voltages to provide electrostatic forces for flexibly moving the diaphragm up and down to move the bridge up and down,

an RF substrate bonded to MEMS substrate for encapsulating the diaphragm, and

a center waveguide comprising a front center waveguide and a back center waveguide separate by a gap and disposed on the RF substrate, the bridge serving to couple the front center waveguide to the back center waveguide when the diaphragm is actuated to bring the bridge down towards the gap and serving to decouple the front center waveguide from the back center waveguide when the diaphragm is actuated to bring the bridge up away from the gap.

2. The switch of claim 1 further comprising,

left and right grounded waveguides extending in parallel to and surrounding the front and back center waveguides for electrically shielding and forming of an RF transmission line with the front and back center waveguides.

3. The switch of claim 1 further comprising,

four suspension arms extending from the diaphragm and coupled to the MEMS substrate for equilaterally suspending the diaphragm.

4. The switch of claim 1 wherein,

the diaphragm has a plurality of apertures for passing partial pressure gas for minimizing resistance to switching motion and damping during flexing of the diaphragm.

5. The switch of claim 1 further comprising,

an insulating dielectric disposed over the gap to isolate the bridge from the front and back center waveguides for providing capacitive coupling between front and back center waveguides for providing capacitive coupling when the bridge is actuated down.

6. The switch of claim 1 wherein,

the bridge making direct physical contact with both the front and back center waveguides for providing DC coupling between the front and back center waveguides.

7. The switch of claim 1 wherein,

the plurality of equilaterally displaced electrodes comprise left and right lower actuator electrodes disposed on the RF substrate, and left and right lower diaphragm actuator electrodes.

8. The switch of claim 7 wherein,

left and right lower actuator electrodes are in vertical alignment with the left and right lower diaphragm actuator electrodes.

9. The switch of claim 7 wherein,

left and right lower actuator electrodes are in vertical alignment with left and right lower diaphragm actuator electrodes, the switch further comprising, and

left and right lower diaphragm actuator electrodes control lines for providing electrostatic potentials for flexing the diaphragm for actuating the bridge up and down.

10. The switch of claim 9 wherein,

the electrostatic potential are modulated for modulating the bridge up and down as the diaphragm flexes up and down for modulating a signal communicated between the front and back center waveguides.

11. The switch of claim 10 wherein the left and right upper actuator electrodes are in vertical alignment with left and right upper diaphragm actuator electrodes, the switch further comprising,

left and right upper diaphragm actuator electrodes control lines and left and right upper actuator electrodes for providing electrostatic potentials for flexing the diaphragm for actuating the bridge up and down.

12. The switch of claim 1 wherein the plurality of equilaterally displaced electrodes comprise,

left and right upper actuator electrodes disposed on the substrate, and

left and right upper diaphragm actuator electrodes.

13. The switch of claim 12 wherein,

the left and right upper actuator electrodes are in vertical alignment with left and right upper diaphragm actuator electrodes.

14. A switch comprising,

a MEMS substrate,

a diaphragm suspended from and attached to the substrate, the diaphragm being suspended equilaterally from the MEMS substrate,

a bridge disposed on the diaphragm, the diaphragm being flexible to move the bridge up and down,

a plurality of equilaterally displaced electrodes surrounding the bridge, the electrodes are controlled by controlling voltages to provide electrostatic forces for flexibly moving the diaphragm up and down to move the bridge up and down,

an RF substrate bonded to MEMS substrate for encapsulating a center waveguide comprising a front center waveguide and a back center waveguide separate by a gap, the bridge serving to couple the front center waveguide to the back center waveguide when the diaphragm is actuated to bring the bridge down towards the gap and serving to decouple the front center waveguide from the back center waveguide when the diaphragm is actuated to bring the bridge up away from the gap,

left and right grounded waveguides extending in parallel to and surrounding the front and back center waveguides for forming a transmission line with the front and back center waveguides,

a plurality of suspension arms extending from the diaphragm and coupled to the RM MEMS substrate for equilaterally suspending the diaphragm, and

an insulating dielectric disposed over the gap to isolate the bridge from the front and back center waveguides for providing capacitive coupling between front and back center waveguides for providing capacitive when the bridge is actuated down.

15. The switch of claim 14 wherein a plurality of equilaterally displaced electrodes comprise,

left and right lower actuator electrodes disposed on the RF substrate,

left and right lower diaphragm actuator electrodes opposing the left and the right lower actuator electrodes,

left and right upper actuator electrodes disposed on the MEMS substrate, and

left and right upper diaphragm actuator electrodes opposing the left and right upper actuator electrodes.

16. The switch of claim 14 wherein,

the left and right lower actuator electrodes and left and right lower diaphragm actuator electrodes and left and right upper actuator electrodes and left and right upper diaphragm actuator electrodes have respective control lines for providing electrostatic potentials between left and right lower actuator electrodes and left and right lower diaphragm actuator electrodes and between left and right upper actuator electrodes and left and right upper diaphragm actuator electrodes, the electrostatic potentials serving to create electrostatic forces for flexing the diaphragm up and down for respectively decoupling and coupling the front and back center waveguides.

17. The switch of claim 16 wherein,

the electrostatic potentials are AC biased potentials for modulating a communication signal communicated between the front and back center waveguides.

18. The switch of claim 17 wherein,

the AC biased potentials contain a DC component for displacing the bridge above the gap and an AC component for modulating the communication signal communicated between the front and back center waveguides.