Method and apparatus for generating a signal having at least one desired output frequency utilizing a bank of vibrating micromechanical devices

• US 6,577,040 B2
• Filed: 04/20/2001
• Issued: 06/10/2003
• Est. Priority Date: 01/14/1999
• Status: Expired due to Term

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Nguyen, Clark T.-C.
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US09/839,035
• Publication Number:
  US 20010030489A1
• Time in Patent Office: 781 Days
• Field of Search: 310/309, 310/328
• US Class Current: 310/309
• CPC Class Codes: H01H 2059/0072 with stoppers or protrusions for maintaining a gap, reducing the contact area or for preventing stiction between the movable and the fixed electrode in the attracted position
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H03H 2009/02511 Vertical, i.e. perpendicular to the substrate plane
• CPC Class Codes: H03H 2009/02519 Torsional
• CPC Class Codes: H03H 2009/02527 Combined
• CPC Class Codes: H03H 3/0078 involving adjustment of the transducing gap
• CPC Class Codes: H03H 9/02409 by application of a DC-bias voltage H03H9/02417 takes precedence
• CPC Class Codes: H03H 9/24 Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive
• CPC Class Codes: H03H 9/2452 Free-free beam resonators
• CPC Class Codes: H03H 9/462 Microelectro-mechanical filters
• CPC Class Codes: H03H 9/465 in combination with other electronic elements
• CPC Class Codes: H03H 9/505 for microelectro-mechanical filters

Abstract

Several MEMS-based methods and architectures which utilize vibrating micromechanical resonators in circuits to implement filtering, mixing, frequency reference and amplifying functions are provided. A method and apparatus are shown for generating a signal having at least one desired output frequency such as LO frequency in an RF subsystem in response to a tuning voltage and without the need for a phase-locking circuit. One of the primary benefits of the use of such architectures is a savings in power consumption by trading power for high selectivity (i.e., high Q). Consequently, the present invention relies on the use of a large number of micromechanical links in SSI networks to implement signal processing functions with basically zero DC power consumption.

Claims

1. A method for generating a signal having at least one desired output frequency in a system in response to a tuning voltage and without the need for a phase-locking circuit, the method comprising:

providing a bank of micromechanical devices wherein each of the devices is switchable between on and off states and tunable;

vibrating one or more of the devices so that each vibrating device generates a signal having an output frequency; and

controllably switching and tuning one or more of the vibrating devices to generate a signal having the at least one desired output frequency in response to the tuning voltage.

2. The method as claimed in claim 1 wherein each of the devices has a Q in excess of 100.

3. The method as claimed in claim 2 wherein each of the devices has a Q in excess of 1000.

4. The method as claimed in claim 1 wherein the devices number more than 10.

5. The method as claimed in claim 4 wherein the devices number more than 100.

6. The method as claimed in claim 5 wherein the devices number more than 1000.

7. The method as claimed in claim 1 wherein the desired output frequency is more than 300 MHz.

8. The method as claimed in claim 1 wherein the step of controllably switching and tuning one or more of the vibrating devices comprises the step of changing an impedance between an input and an output of one of the vibrating devices.

9. The method as claimed in claim 1 wherein each of the devices has an adjustable Q and wherein the method further comprises lowering the Q of the at least one vibrating device having the at least one desired output frequency initially during the step of vibrating and then raising the Q during the step of vibrating.

10. The method as claimed in claim 9 wherein the step of lowering includes the step of controllably coupling at least one circuit element to the at least one vibrating device having the at least one desired frequency and the step of raising includes the step of controllably decoupling the at least one circuit element from the at least one vibrating device having the at least one desired frequency.

17. The method as claimed in claim 1 wherein each of the devices has a Q greater than 5000.

11. A local oscillator synthesizer apparatus for generating a signal having at least one desired output frequency in a system in response to a tuning voltage and without the need for a phase-locking circuit, the apparatus comprising:

a parallel bank of micromechanical resonators, each of the resonators corresponding to a frequency and wherein each of the resonators is switchable between on and off states and tunable; and

a controller for controllably switching and tuning at least one desired resonator of the bank of resonators to thereby provide frequency selection.

12. The apparatus as claimed in claim 11 further comprising an oscillator sustaining circuit wherein each of the resonators is switchable into or out of the oscillator sustaining circuit by the controller.

13. The apparatus as claimed in claim 11 wherein the controller includes a decoder for controlling application of an appropriate bias voltage to the at least one desired resonator.

14. The apparatus as claimed in claim 11 wherein the resonators are interlinked and wherein each of the resonators has an input connected to a common input and each of the resonators has an output connected to a common output.

15. The apparatus as claimed in claim 11 wherein each of the resonators has a predetermined Q and wherein the controller also selectively switches at least one circuit element to the at least one desired resonator to lower the Q of the at least one desired resonator from its predetermined Q and selectively switches the at least one circuit element from the at least one desired resonator to raise the Q of the at least one desired resonator to its predetermined Q.

16. The apparatus as claimed in claim 11 wherein the frequency of each of the resonators is switchable and tunable.

18. The apparatus as claimed in claim 13 wherein the at least one desired resonator has an input electrode, an output electrode, and an impedance between the input electrode and the output electrode;

and

the appropriate bias voltage changes the impedance to select the at least one desired resonator.

19. A method for generating a signal in response to a control voltage, the method comprising:

providing a plurality of micromechanical resonator devices, each micromechanical resonator device having an input, an output, and an impedance between the input and the output and responsive to the control voltage;

controllably selecting a desired micromechanical resonator device of the plurality of micromechanical resonator devices by providing the control voltage to the desired micromechanical resonator device to modify the impedance of the desired micromechanical resonator device and thereby enable the desired micromechanical resonator device for operation; and

driving the desired micromechanical resonator device to generate the signal.

20. The method as claimed in claim 19 wherein the control voltage is a DC bias voltage.

21. The method as claimed in claim 21 wherein the impedance of a micromechanical resonator device of the plurality of micromechanical resonator devices other than the desired micromechanical resonator device is that of a substantially open circuit to input signals provided to the input thereof.

22. An apparatus for generating a signal having an output frequency, the apparatus comprising:

a plurality of micromechanical resonator devices wherein each micromechanical resonator device has an input, an output, and an impedance between the input and the output; and

a controller that generates a control signal to modify the impedance of a desired micromechanical resonator device of the plurality of micromechanical resonator devices to select the desired micromechanical resonator device for generation of the signal.

23. The apparatus as claimed in claim 22 wherein the controller includes a decoder that controls application of the control signal to the desired micromechanical resonator device.

24. The apparatus as claimed in claim 22 wherein the control signal is a DC bias voltage.

25. The apparatus as claimed in claim 24 wherein the impedance of a micromechanical resonator device of the plurality of micromechanical resonator devices other than the desired micromechanical resonator device is that of a substantially open circuit to input signals provided to the input thereof.