Reference oscillator frequency stabilization

• US 20050184822A1
• Filed: 02/02/2005
• Published: 08/25/2005
• Est. Priority Date: 02/03/2004
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Mattila, Tomi, Seppa, Heikki, Oja, Aarne, Jaakkola, Olli
• Granted Patent: US 7,248,128 B2
• Time in Patent Office: Days
• US Class Current: 331/175
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 2009/02503 Breath-like, e.g. Lam? mode, wine-glass mode
• CPC Class Codes: H03H 9/02244 of microelectro-mechanical resonators
• CPC Class Codes: H03H 9/38 with adjustable delay time H03H9/40, H03H9/42 take precedence
• CPC Class Codes: H03L 1/022 by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature H03L1/021 takes precedence
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or phase-locked loop
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop

Abstract

Method for stabilizing the frequency of a MEMS (Micro Electro Mechanical Systems) reference oscillator, and a MEMS reference oscillator, wherein the method comprises following steps: using two or more MEMS components, wherein each MEMS component is characterized by a set of properties, and selectively combining the desired properties from the MEMS components.

Claims

1. Method for stabilizing the frequency of a MEMS (Micro Electro Mechanical Systems) reference oscillator, characterised in that the method comprises following steps:

using two or more MEMS components, wherein each MEMS component is characterized by a set of properties, and

selectively combining the desired properties from the MEMS components.

2. Method for stabilizing the frequency of a MEMS reference oscillator according to claim 1, characterised in that a combiner or alike synthesizes the desired output by a selective combination of the properties in the components.

3. Method for stabilizing the frequency of a MEMS reference oscillator according to claim 2, characterised in that the combiner or alike processes the oscillators'"'"' signals.

4. Method for stabilizing the frequency of a MEMS reference oscillator according to claim 2, characterised in that the combiner or alike uses feedback adjustment of the oscillators.

5. Method for stabilizing the frequency of a MEMS reference oscillator according to claim 2, characterised in that the combiner or alike utilizes additional inputs such as the measured temperature of the oscillators.

6. Method for stabilizing the frequency of a MEMS reference oscillator according to claim 2, characterised in that a tunable oscillator based on a micromachined resonator creates the low phase noise output signal, and the long-term stability for the oscillator is provided by a frequency meter that monitors the frequency of the oscillator and adjusts frequency to the desired reference value.

7. Method for stabilizing the frequency of a MEMS reference oscillator according to claim 2, characterised in that the oscillator output frequency is synthesized from the frequencies of two oscillators, both of which are based on micromachined resonators and the properties of the output signal are dominantly derived from the high-frequency oscillator that provides the long-term stability and the low phase noise.

8. Method for stabilizing the frequency of a MEMS reference oscillator according to claim 7, characterised in that that the output frequency of the high-frequency oscillator is left untuned, and the compensation for temperature and fabrication offsets is performed using frequency summing.

9. Method for stabilizing the frequency of a MEMS reference oscillator according to claim 8, characterised in that to obtain constant and precise frequency output signal the frequency from a low-frequency tunable oscillator summed with the high-frequency oscillator output.

10. MEMS (Micro Electro Mechanical Systems) reference oscillator with stabilized frequency, characterised in that the oscillator comprises:

two or more MEMS components, wherein each MEMS component is characterized by a set of properties, and

a combiner or alike for selective combination of the desired properties from the MEMS components.

11. MEMS reference oscillator according to claim 10, characterised in that at least one of the components is a micromechanical bulk acoustic mode silicon resonator with a square plate and electrodes for capacitive coupling arranged on all sides of the plate, wherein the vibration mode is characterised as a 2-D plate expansion that preserves the original square shape.

12. MEMS reference oscillator according to claim 10, characterised in that the type of at least one MEMS component is different from the types of the other MEMS components.

13. MEMS reference oscillator according to claim 10, characterised in that the components are identical but their control parameters, such as bias voltage, are different.

14. MEMS reference oscillator according to claim 10, characterised in that the oscillator utilizes a stable frequency reference based on an bulk acoustic mode oscillator and a frequency meter operation based on comparing the frequency created by the bulk acoustic wave oscillator with the output frequency of the tunable oscillator.

15. MEMS reference oscillator according to claim 10, characterised in that the oscillator utilizes a stable frequency reference obtained by measuring the phase difference of propagating bulk acoustical wave in a micromachined sound-wave guide at fixed positions.

16. MEMS reference oscillator according to claim 10, characterised in that the oscillator utilizes a frequency meter based on stable capacitors and stable micromachined thin-film resistors that are used to create the Wien oscillator topology.

17. MEMS reference oscillator according to claim 10, characterised in that a capacitor-resistor network, that is part of the Wien oscillator circuit, is used as a frequency meter in which the capacitors and resistors form a bridge circuit the balance of which depends on the frequency of the incoming frequency.

18. MEMS reference oscillator according to claim 10, characterised in that the oscillator output frequency is synthesized from the frequencies of two MEMS oscillators, wherein the properties of the output signal are dominantly derived from the high-frequency oscillator that provides the long-term stability and the low phase noise, and wherein the output frequency of the high-frequency oscillator is left untuned, and the compensation for temperature and fabrication offsets is performed using frequency summing.

19. MEMS reference oscillator according to claim 18, characterised in that the frequency from a low-frequency tunable oscillator summed with the high-frequency oscillator output.