WO2010003605A1

WO2010003605A1 - Micro-electromechanical oscillator

Info

Publication number: WO2010003605A1
Application number: PCT/EP2009/004856
Authority: WO
Inventors: Lin He; Alexander Buhmann; Yiannos Manoli; Armin Taschwer; Thomas Northemann
Original assignee: Albert-Ludwigs-Universität Freiburg
Priority date: 2008-07-07
Filing date: 2009-07-06
Publication date: 2010-01-14
Also published as: DE102008036191A1

Abstract

A micro-electromechanical oscillator has an oscillation exciter which has an actuator (7a, 7b) and a control unit (10) thereto. The actuator (7a, 7b) has a driven connection to a mass (2) to be caused to oscillate. To detect a measured signal dependent on the oscillation of the mass (2), a measuring apparatus (8) is provided which is connected to the control device (10) in an oscillator-control circuit in such a manner that the mass (2) is caused to oscillate at a resonance frequency. The measuring apparatus (8) comprises a micro-electromechanical capacitive sensor (9a, 9b) having electrodes which can be moved toward and away from each other as a function of the deflection of the mass (2). The measuring apparatus (8) has a position sensor interface which is arranged in the oscillator-control circuit and is connected to an input junction (15a, 15b), to the sensor (9a, 9b) and to an output junction (20a, 20b) to the control device (10). A phase shifter is provided in the oscillator control circuit.

Description

Microelectromechanical oscillator

The invention relates to a microelectromechanical oscillator having a vibration exciter, which has at least one actuator and a drive device for it, wherein the actuator is in drive connection with a mass to be vibrated, with a measuring device for detecting a dependent on the vibration of the mass measurement signal, wherein the measuring device is connected to the control device in an oscillator control loop, that the mass is excited to vibrate at a resonant frequency, wherein the measuring device comprises at least one microelectromechanical capacitive sensor having electrodes which in dependence on the deflection of the mass toward and away from each other are movable.

Such an oscillator is known from Green, J. et al. "Single-Chip Surfdce Micromachined Integrated Gyroscopes With 50 ° / h Allan Deviation", IEEE Journal of Solid-State Circuits, Vol. 37, No. 12 (2002), pages 1 800-1 866. The oscillator is part of a gyroscope, which has a movably mounted mass which can be deflected from a rest position against a spring force of a first spring in the direction of a first axis and at right angles thereto against a spring force of a second spring in the direction of a second axis The movement of the mass in the direction of the first axis is measured by means of a primary capacitive sensor The sensor is designed as a differential sensor with a noninverting first measuring signal output and an inverting second measuring signal output.

The measuring signal of the sensor is amplified by means of an operational amplifier. It has a noninverting amplifier input, an inverting amplifier input, a noninverting amplifier output and an inverting amplifier output. The non-inverting amplifier output is connected to the inverting amplifier input via a first ohmic feedback resistor. Similarly, the inverting amplifier output is connected to the non-inverting resistor via a second resistive feedback resistor. connecting amplifier input. As a function of the measurement signal thus obtained, a square-wave voltage is generated and applied to an actuator that sets the mass in the direction of the first axis in oscillation. The phase position of the square-wave voltage is chosen such that the mass is excited to vibrate at a resonant fundamental frequency. When the oscillator is switched on, the oscillation is started by the noise contained in the output signal of the operational amplifier.

Rotation of the mass about an axis of rotation perpendicular to the first axis and the second axis produces a Coriolis force which causes secondary oscillation of the mass in the direction of the second axis. The corresponding deflection is measured by means of a secondary capacitive sensor whose measuring signal is amplified by means of a measuring amplifier.

The oscillator has the disadvantage that, due to the phase response of its control circuit, it can also be excited to oscillate with a spurious oscillation whose frequency is higher than the resonant fundamental frequency. In the case of the spurious vibration, however, the measuring device has a lower sensitivity than at the fundamental resonance frequency. It is also unfavorable that the oscillator still has a relatively large phase noise, which causes a Ditter the oscillator oscillation. In addition, the power consumption is still relatively high.

There is therefore the object to provide an oscillator of the type mentioned, in which the risk that the oscillator oscillates at a natural resonant frequency which is higher than the resonant fundamental frequency, avoided or at least reduced. In addition, the oscillator should allow low power consumption and low phase noise.

This object is achieved in that the measuring device in the oscillator control loop has a position sensor interface, which is connected to at least one input terminal to the sensor and at least one output terminal to the drive means, and that in the oscillator control loop, a phase shifter is provided , A position sensor interface is understood to be a circuit which provides a signal corresponding to the position of the oscillating mass. By connected in the oscillator control loop position sensor interface and thus connected in series phase shifter, the loop gain of the oscillator control loop is reduced at high frequencies, whereby the risk that the actuator and thus standing in driving connection oscillatory mass with a frequency above the Resonance zurrundfrequenz is excited to the vibration is reduced. The phase shift of the phase shifter is chosen such that a resonant circuit is formed and is preferably about 90 °. The position sensor interface is preferably designed as a charge integrator and in particular as a time-continuous charge integrator, which allows a low noise in the oscillator control loop and thus a correspondingly lower current consumption of the oscillator. The oscillator is therefore particularly well suited for battery or battery operation.

Advantageously, the microelectromechanical oscillator according to the invention can also be used as a reference oscillator or clock. This oscillator according to the invention has the advantage over a conventional quartz oscillator that it can easily be integrated into a semiconductor chip together with other electronic circuit components by means of a standard semiconductor process. This can significantly reduce the cost of providing the reference oscillator and thus the total cost of an electronic circuit. In addition, the microelectromechanical oscillator according to the invention has the advantage that it consumes much less power than a corresponding quartz oscillator.

In one embodiment of the invention, an actuator for adjusting the loop gain of the oscillator control loop is preferably arranged in the oscillator control loop between the position sensor interface and the phase shifter, wherein the actuator is in control connection with an amplitude controller for the oscillator control loop. With the aid of the amplitude control loop, the loop gain of the oscillator control loop is set to be approximately equal to 1 at the resonant frequency of the oscillator and to be less than 1 at frequencies well above the resonant fundamental frequency, so that Oscillator can oscillate only at the resonance frequenzrundfrequenz. It is advantageous if the phase shifter is designed as an integration amplifier. This results in a low noise in the oscillator control loop.

In a preferred embodiment of the invention, the actuator for adjusting the loop gain of the oscillator control loop between the output terminal of the position sensor interface and an input of the phase shifter is arranged. This results in a simple structure of existing from the control device and the measuring device electrical circuit.

In a further development of the invention, the adjusting element for adjusting the loop gain comprises a multiplier which is connected to the output terminal of the position sensor interface with a first multiplier input, to a second multiplier input to a regulator output of an amplitude regulator and to a multiplier output to the input of the phase shifter is, wherein the amplitude controller has a connected to the output terminal of the position sensor Interfdces controller input. The loop gain in the oscillator loop is then automatically set to the value 1 at the resonant fundamental frequency such that the oscillator oscillates at the resonant fundamental frequency and that the control loop attenuates higher order frequencies.

In an expedient embodiment of the invention, the multiplier has a voltage-controlled current source; in particular, a silver cell. The multiplier can then be inexpensively integrated into a semiconductor chip.

The amplitude controller preferably has a rectifier, which is connected with a rectifier input to the output terminal of the position sensor Interfdces and with a rectifier output with a loop filter and subsequently to the second multiplier input. Also by this measure, an automatic adjustment of the loop gain in the oscillator control loop is made possible in a simple manner.

It is advantageous if between the rectifier output and the second multiplier Ziergliedeingang an adder and / or subtractor is arranged with the a first input directly or indirectly connected to the rectifier output, to a second input to a reference value transmitter and to an output directly or indirectly connected to the second multiplier input. The reference value for the loop gain can then be specified with the aid of the reference value transmitter. If the amplitude is greater than the setpoint, the loop gain in the oscillator loop is automatically reduced, and if the amplitude is greater than the setpoint, the loop gain in the oscillator loop is automatically increased.

It is advantageous if the position sensor interface comprises an operational amplifier having at least the input terminal forming amplifier input and at least one output terminal forming the amplifier output, which is fed back via at least one integration capacitor to the input terminal, and if the at least one input terminal via a high-resistance electrical resistance with connected to a terminal for an electrical common-mode reference potential. Thereby, it is possible to set the common mode reference potential to a predetermined value and thereby adjust the resonance frequency of the primary resonator formed of the mass and the first spring. As a result, it is even possible to match the resonant fundamental frequency of the primary resonator formed from the mass and the first spring and the resonant frequency of the secondary oscillator formed from the mass and the second spring to one another. Since a resetting of the integration capacitor is not required due to the resistors connected to the common-mode reference potential, the integration capacitor can be used without interruption for the measurement. The measuring device also allows a defined DC voltage level at the output of the operational amplifier. Furthermore, the measuring device is insensitive to a furnace voltage of the sensor.

It is advantageous if the high-resistance electrical resistance is formed by a FET, in particular a MOSFET, which connects with its source-drain path the input terminal to the terminal for the common-mode reference potential and is applied with its gate to a control voltage. The high-impedance resistor can thereby cost-effective and space-saving together with the Operational amplifier and optionally further electrical circuit components are integrated into a semiconductor chip.

Conveniently, the control voltage is less than the threshold voltage of the MOSFET. This allows a very high resistance electrical resistance.

In a preferred embodiment of the invention, the measuring device for generating the control voltage has a voltage source whose source output is connected to the gate of the MOSFET, the voltage source having a control input which is in control connection with the common-mode reference potential terminal in the event of a change of the common mode reference potential, the electrical resistance of the source-drain path of the MOSFET remains substantially constant. The common mode reference potential can then be easily adjusted without changing the value of the high resistance electrical resistance.

In an advantageous embodiment of the invention, the capacitive sensor is a differential sensor having a noninverting first measuring signal output and an inverting second measuring signal output and the operational amplifier as a differential operational amplifier having a non-inverting first input terminal, an inverting second input terminal, a non-inverting first output terminal and an inverting second output terminal. The first measurement signal output is connected to the first input terminal and the second measurement signal output is connected to the second input terminal, wherein the first output terminal is fed back via a first integral capacitor to the second input terminal and the second output terminal via a second integration capacitor to the first input terminal. and wherein the first input terminal via a high-resistance first resistor and the second input connected via a high-resistance second resistor to the terminal for the common-mode reference potential. The measuring device is thus designed as a differential measuring device and thereby enables a greater measuring sensitivity. The high-impedance resistors preferably have approximately the same resistance value Advantageously, in addition to the first input terminal, the operational amplifier has a first non-inverting help input and a second inverting help input in addition to the second input terminal, the second output terminal being connected to a non-inverting first lowpass input of a lowpass and the first output terminal being connected to an inverting second lowpass input of the lowpass filter, and wherein a non-inverting first low-pass output is connected to the first auxiliary input and an inverting second low-pass output of the low-pass is connected to the second auxiliary input. The operating point of the operational amplifier is set with a low-pass filtered signal, so that the auxiliary inputs associated circuit parts of the operational amplifier can be designed low frequency.

However, it is also possible for the operational amplifier to have, in addition to the first input terminal, a first non-inverting auxiliary input and a second inverting help input in addition to the second input terminal, the second output terminal having an inverting first low-pass input of a low-pass filter and the first output connector having a non-inverting second low-pass input the low-pass filter is connected, and wherein an inverting first low-bass output is connected to the first auxiliary input and a non-inverting second low-pass output of the low-pass filter is connected to the second auxiliary input. Also in this embodiment of the invention, the operating point of the operational amplifier is adjusted with a low-pass filtered signal.

It is advantageous if the second output terminal is connected via a first resistor element to the first low-pass input and the first output terminal via a second resistor element to the second Tiefbasseingang, and if the first Tiefbasseingang is connected via a third resistor element to the second Tiefpasseingang. The resistor network thus formed allows a measuring device whose output signal has a high amplitude. Advantageously, the low-pass filter has at least one voltage-controlled current source whose output is connected to an integral input of a Miller integrator. The low pass can thus be better integrated into a semiconductor chip. A complex and expensive external capacitor can be saved.

In a preferred embodiment of the invention, the first low-pass input is connected to an input of a first transconductor and the second low-pass input to an input of a second transconductor, wherein the first low-pass output is connected to an output of the first transconductor and the second low-pass output to an output of the second transconductor , and wherein the output of the second transconductor is connected via a first counter coupling branch to a first negative input terminal of the first transconductor and the output of the first transconductor via a second negative feedback branch to a second negative terminal terminal of the second transconductor. The measuring device thereby enables a high output amplitude and a largely linear amplification of the sensor measurement signal.

An exemplary embodiment of the invention is explained in more detail below with reference to the drawing. It shows

1 shows a schematic representation of a gyroscope which has a microelectrical oscillator and a measuring device for measuring a deflection of a mass caused by a Coriolis force,

2 is a block diagram of the microelectromechanical oscillator,

3 shows a circuit diagram of a measuring device for measuring a primary oscillation of the mass of the oscillator,

4 shows a circuit diagram of an amplifier circuit for a charge integrator, the amplifier circuit having an operational amplifier whose output is fed back via a low-pass filter to the amplifier input of the operational amplifier, FIG. 5 shows a circuit diagram of a transconductance amplifier (Gm cell) of the low-pass filter, FIG.

FIG. 6 shows a circuit diagram of an integration amplifier with adjustable gain, FIG.

7 is a circuit diagram of an amplitude controller of the oscillator, and

8 shows a graph of the loop gain and the phase transition of an oscillator control loop, the abscissa representing the angular frequency and the ordinate the gain M in dB or the phase angle φ in degrees.

A gyroscope, denoted as a whole by 1 in FIG. 1, has an oscillator with a mass 2, which is micromechanically attached to a non-illustrated in the drawing

Holder along a first axis 3 against the restoring force of a pair of first springs 4 and along a perpendicular thereto extending second axis 5 against the Rückstellkraff a pair of second springs ό is mounted deflected from a rest position. The holder may for example be a semiconductor chip, on or in which the mass 2 is arranged.

The oscillator has a vibration exciter, by means of which the mass 2 is caused to oscillate about the rest position in the direction of the first axis 3. The vibration exciter comprises capacitive actuators 7a, 7b, each having a first and a second electrode. The first electrode is respectively connected to the holder and the second electrode is respectively connected to the mass 2.

In order to detect a measurement signal which depends on the oscillation of the mass, the oscillator has a measuring device 8 which has primary capacitive sensors 9a, 9b. In Fig. 1 it can be seen that the mass 2 is arranged between the primary sensors 9a, 9b. Each primary sensor 9a, 9b has a first electrode connected to the ground 2 and a second electrode connected to the holder. When the mass 2 is displaced from its rest position in the direction of the first axis 3, the electrodes of the one primary sensor 9a, 9b move towards each other and the electrodes of the other primary sensor 9b, 9a move away from each other. As a result, the measurement signals of the primary sensors' 9a, 9b change in mutually opposite directions.

The measuring device 8 is connected in such a way with a control device 10 driving the actuators 7a, 7b into an oscillator control loop, that the mass 2 is excited to oscillate with a resonant fundamental frequency.

When the holder and thus the position of the mass 2 is rotated about a rotation axis arranged normal to the first axis 3 and to the second axis 5, a Coriolis force acting on the mass 2 acts in the direction of the second axis 5 and the mass 2 counteracts the restoring forces the second springs 6 deflected in the direction of the second axis 5 from the rest position.

To measure this deflection, the gyroscope 1 has a measuring device 1 1; which comprises two secondary microelectromechanical capacitive sensors 12a, 12b and an evaluation circuit 1 3 connected thereto. In Fig. 1 it can be seen that the mass 2 is arranged between the secondary sensors 12a, 12b. Each secondary sensor 12a, 12b has a first electrode connected to the proof mass 2 and a second electrode connected to the support.

When the mass 2 is shifted in the direction of the second axis 5 from its rest position, move the electrodes of a secondary sensor 1 2a, 1 2b towards each other and the electrodes of the other secondary sensor 12b, 12a away from each other. As a result, the measurement signals of the secondary sensors 12b, 12a change in mutually opposite directions.

As can be seen in FIG. 3, a first electrode of a first primary sensor 9a forming a first measuring signal output is connected via a first protective circuit 14a to a noninverting input terminal 1a of a charge integrator 1ό serving as a position sensor interface. A second electrode of the first primary sensor 9a is connected to a terminal 1 7 for a reference potential. In a corresponding manner, a first electrode of a second primary sensor 9b forming a second measuring signal segment is connected to an inverting input terminal 15b of the charge integrator 16 via a second protective circuit 14b. A second electrode of the second primary sensor 9b is connected to the terminal 17 for the reference potential. ■

The charge integrator 1 ό has a first operational amplifier 18 whose non-inverting output terminal 20a is connected via a first integration capacitor 19a to an inverting amplifier input of the first operational amplifier 18 forming the input terminal 15b. An inverting output terminal 20b of the first operational amplifier 18 is connected via a second integration capacitor 19b to a non-inverting amplifier input of the first operational amplifier 18 forming the input terminal 15a. It can clearly be seen that neither to the first integration capacitor 19a nor to the second integration capacitor 19b, an electrical resistance is connected in parallel.

The non-inverting input terminal 15a is connected via a first electrical resistance 21a to a terminal 22 for an electrical common-mode reference potential. In a corresponding manner, the inverting input terminal 15b is connected via a second electrical resistance 21 b to the connection 22 for the electrical common-mode reference potential.

The resistors 21 a, 21 b are each formed by the source-drain path of a MOSFET. The θate electrodes of the MOSFETs are connected to a voltage source 23, which provides a control voltage that is smaller in magnitude than the threshold voltage of the MOSFETs.

The common mode reference potential is adjustable and is generated by means of a reference voltage source not shown in the drawing. By varying the common mode reference potential, the resonant frequency of the primary oscillator formed from the first springs 4 and the mass 2 can be tuned to the resonant frequency of the secondary formed from the second springs ό and the masses 2 and Resonator be tuned. This allows a high sensitivity of the measuring device 1 1.

The first operational amplifier 118 has, in addition to the noninverting input terminal 15a, a noninverting help input 24a and an inverting help input 24b in addition to the inverting input terminal 15b. The inverting output terminal 20b is connected to a noninverting lowbass input 26a of a low bass 27 via a first resistive element 25a. The non-inverting output terminal 20a is connected via a second resistor element 25b to an inverting low-bass input 26b of the low-pass filter 27.

A third resistance element 25c connects the non-inverting input terminal 26a to the inverting input terminal 2όb of the low-pass filter 27. This allows a larger output amplitude of the first operational amplifier 18.

To set the operating point of the first operational amplifier 18, a non-inverting low-pass output 28a of the low-pass filter 27 is connected to the non-inverting help input 24a of the first operational amplifier 118 and an inverting second low-pass output 28b of the low-pass filter 27 is connected to the inverting help input 24b of the first operational amplifier 18.

4, it can be seen that the non-inverting help input 24a of the first operational amplifier 18 is formed by the gate of a first MOSFET 29a, to the source-drain path of which a first current source 30a is connected in parallel. The

Source of the first MOSFET 29a is connected to a first supply voltage terminal. With the source-drain path of a first MOSFET 29a is the

Source-drain path of a second MOSFET 31 a connected in series, the gate of which forms the inverting input terminal 15 b.

In a first circuit branch connecting the drain of the first MOSFET 29a to the drain of the second MOSFET 31a, the non-inverting output terminal 20a is arranged. The source of the second MOSFET 31 a is connected via a second current source 30 b to a second supply voltage terminal. The inverting auxiliary input 24b of the first operational amplifier 118 is formed by the gate of a third MOSFET 29b to whose source-drain path a third current source 30c is connected in parallel. The source of the third MOSFET 29b is connected to the first supply voltage terminal. Connected in series with the source-drain path of the third MOSFET 29b is the source-drain path of a fourth MOSFET 31b whose gate forms the non-inverting input connection 15a of the charge integrator 1 '. In a second circuit branch connecting the drain of the third MOSFET 29b to the drain of the fourth MOSFET 31b, the inverting output terminal 20b is arranged. The source of the fourth MOSFET 31 b is connected via the second current source 30 b to the second supply voltage terminal.

It can also be seen in FIG. 4 that the low-pass filter 27 has a first voltage-controlled current source 32 (Gm cell) with a noninverting input 33a and an inverting input 33b. The noninverting input 33a is connected to the inverting output terminal 20b and the inverting input 33b to the noninverting output terminal 20a of the first operational amplifier 118.

The first voltage controlled current source 32 further includes a non-inverting output 34a and an inverting output 34b. The noninverting output 34a is across the source-drain path of a fifth MOSFET 35a having the first supply voltage terminal and the inverting output 34b is across the source-drain path of a sixth MOSFET 35b connected to the first supply voltage terminal. Non-inverting output 34a is connected to a first input of miller integrator 36 and inverting output 34b to a second input of miller integrator 36. The two outputs 34a, 34b are also each connected to a terminal of a first Hilftschaltung 37. At the first auxiliary circuit 37, the gates of the fifth MOSFET 35a and sixth MOSFETs 35b are also connected.

5, it can be seen that the first voltage-controlled current source 32 has a first tranconductor 38a and a second transconductor 38b. The non-inverting low-pass input 26a is connected to an input of the first transponder. conductors 38α and the inverting low-pass filter 26b is connected to an input of the second transconductor 38b.

The non-inverting low-pass output 28a is connected to the non-inverting output 34a of the first transconductor 38a and the inverting low-pass output 28b to the inverting output 34b of the second transconductor 38b. The output 34b of the second transconductor 38b is connected via a first negative feedback branch 39a to a first reverse-connection terminal 40a of the first transconductor 38a and the output 34a of the first transconductor 38a to a second reverse-input terminal 40b of the second transconductor 38b via a second cross-coupling branch 39b. The negative feedback enables a better linearization of the measurement signals of the primary sensors 9a, 9b.

The output 34a is connected to a reference potential terminal 43 via a first path comprising a source-drain path of a first FET 41a and a fourth current source 42a connected in series therewith. The output 34b is connected to the reference potential terminal 43 via a second path comprising a source-drain path of a second FET 41b and a fifth current source 42b connected in series therewith.

FIG. 2 shows that the control device 10 of the actuators 7a, 7b has an integration amplifier 44, which is arranged in the oscillator control circuit between the output terminal 20a, 20b of the charge integrator 16 and the actuators 7a, 7b.

Between the output terminals 20a, 20b of the charge integrator 16 and an input of the integration amplifier 44, an actuator 45 is arranged for adjusting the loop gain of the oscillator control loop. The actuator 45 has a multiplier 46, which is arranged between the charge integrator 16 and the integration amplifier 44 in the oscillator control loop. The multiplier 46 has differential first multiplier inputs 47a, 47b, a second multiplier input 48 and a differential multiplier output 49a, 49b. The Ausgαngsαnschlüsse 20α, 20b of the charge integrator 16 are each connected to a first multiplier input 47a, 47b and additionally via an amplitude regulator 50 to the second multiplier input 48. The multiplier outputs 49a, 49b are connected to differential inputs of the integration amplifier 44 in such a way that the position measuring signal of the mass 2 detected with the aid of the sensors 9a, 9b is forwarded to the actuators 7a, 7b in the form of a negative position signal. The position measuring signal is thus fed back in negative or inverted form to the actuators 7a, 7b.

In Fig. Ό it can be seen that the multiplier 46 has a Gilbert cell, which is connected to a second auxiliary circuit 51. In addition, it can be seen that the integration amplifier 44 has a second operational amplifier 52 whose non-inverting output is connected via a third integration capacitor 53a to an inverting amplifier input of the second operational amplifier 52. Similarly, an inverting output of the second operational amplifier 52 is connected to a noninverting amplifier input of the second operational amplifier 52 via a fourth integrating capacitor 53b. The differential outputs of the second operational amplifier 52 are also coupled to the second auxiliary circuit 51 via a low-pass circuit 54.

In FIG. 7 it can be seen that the amplitude regulator comprises a full-wave rectifier 55 which has differential rectifier inputs 56a, 5b which are connected to the output terminals 20a, 20b of the charge integrator 16 via a second voltage-controlled current source 60. An θgleichrichterausgang 57 of the full-wave rectifier 55 is also connected via a designed as a high-pass loop filter 58 to a reference potential. At the rectifier output 57, a sixth current source 59 is connected, by means of which the gain in the oscillator control loop is controlled. Furthermore, the rectifier output 57 is connected to the second multiplier input 48 in order to apply a setting signal for setting the loop gain to the second multiplier input 48.

In FIG. 8 it can be seen that the loop gain of the oscillator control loop has a maximum at the resonant fundamental frequency of the primary resonator formed from the first springs 4 and the mass 2 and that this maximum is equal to 1. At the first harmonic fundamental resonant frequency, the loop gain is severely attenuated and less than 1. For higher order harmonics, the oscillator loop attenuates the oscillation even more. This ensures that the primary resonator is always excited by the actuators 7a, 7b at the resonant fundamental frequency.

The microelectromechanical oscillator thus has a vibration exciter which has at least one actuator 7a, 7b and a drive device 10 therefor. The actuator 7a, 7b is in drive connection with a mass 2 to be vibrated. The oscillator has a measuring device 8 for detecting a dependent of the vibration of the mass 2 measuring signal. The measuring device 8 is connected to the control device 10 in an oscillator control loop such that the mass 2 is excited to vibrate at a resonant frequency. The measuring device 8 comprises at least one microelectromechanical capacitive sensor 9a, 9b, which has electrodes which are movable towards and away from one another as a function of the deflection of the mass 2. The measuring device 8 has a charge integrator 1 ό; which is arranged in the oscillator control loop and is connected to at least one input terminal 1 5a, 1 5b to the sensor 9a, 9b and at least one output terminal 20a, 20b to the drive means 1 0. The drive device 10 has an integration amplifier 44 in the oscillator control loop. In addition, an actuator 45 for adjusting the loop gain of the oscillator control loop is arranged in the oscillator control circuit. The actuator 45 is in control connection with an amplitude regulator 50 for the oscillator control loop.

Claims

claims

1. Mikroelektrornechanischer oscillator with a vibration exciter, the at least one actuator (7a, 7b) and a drive means (1 0) therefor, wherein the actuator (7a, 7b) to be offset with a to be vibrated

Mass (2) is in drive connection, with a measuring device (8) for detecting a dependent of the vibration of the mass (2) measuring signal, the measuring device (8) is so connected to the drive means (1 0) in an oscillator control loop, in that the mass (2) is excited to oscillate at a resonant frequency, wherein the measuring device (8) comprises at least one microelectromechanical capacitive sensor (9a, 9b) having electrodes facing one another in dependence on the deflection of the mass (2) are movable away from one another, characterized in that the measuring device (8) in the oscillator control loop has a position sensor Interfdce with at least one input terminal (1 5a, 1 5b) with the sensor (9a, 9b) and at least one Output terminal (20a, 20b) with the drive means (1 0) is connected, and that in the oscillator control loop, a phase shifter is provided.

2. Microelectromechanical oscillator according to claim 1, characterized in that in the oscillator loop preferably between the position sensor Interfdce and the phase shifter an actuator (45) for adjusting the loop gain of the oscillator control loop is arranged, and that the actuator (45) with a Amplitude regulator (50) for the oscillator control loop is in control connection.

3. Microelectromechanical oscillator according to claim 1 or 2, characterized in that the phase shifter is preferably designed as an integration amplifier (44).

4. Microelectromechanical oscillator according to one of claims 1 to 3, characterized in that the actuator (45) for adjusting the loop gain of the oscillator control loop between the output terminal (20a, 20b) of the position sensor interface and an input of the phase shifter is arranged ,

5. Mikroelektromechαnischer oscillator according to one of claims 1 to 4, characterized in that the actuator (45) for adjusting the loop gain comprises a multiplier (46) having a first multiplier member input (47a, 47b) with the output terminal (20a, 20b) of the position sensor interface, having a second multiplier input (47b) connected to a regulator output of an amplitude regulator (50) and a multiplier output (49a, 49b) connected to the input of the phase shifter, the amplitude regulator (50) connected to the output connector (50). 20a, 20b) of the position sensor interface has associated controller input.

ό. Microelectromechanical oscillator according to one of claims 1 to 5, characterized in that the multiplier (46) comprises a voltage-controlled current source, in particular a Gilbert cell.

7. The microelectromechanical oscillator according to claim 1, characterized in that the amplitude regulator (50) has a rectifier (55) which is connected to a rectifier input (56a, 56b) to the output terminal (20a, 20b) of the position sensor. Interfaces and with one

Rectifier output (57) is connected to a loop filter and subsequently to the second multiplier input.

8. Microelectromechanical oscillator according to one of claims 1 to 7, characterized in that between the rectifier output (57) and the second multiplier input (47b) an adder and / or subtractor is arranged, with a first input directly or indirectly with the rectifier output (57), having a second input connected to a reference value transmitter and having an output directly or indirectly connected to the second multiplier input (47b).

9. microelectromechanical oscillator according to one of claims 1 to 8, characterized in that the position sensor interface comprises an operational amplifier (1 8), the at least the input terminal (1 5a, 1 5b) forming the amplifier input and at least one of the Ausgangsan Closing (20α, 20b) Verstörkerαusgαng has the at least one integration capacitor (19a, 19b) is fed back to the input terminal (1 5a, 1 5b), and that the at least one input terminal (1 5a, 1 5b) via a high-resistance electrical resistance (21 a, 21 b) is connected to a terminal (22) for an electrical common-mode reference potential.

10. Microelectromechanical oscillator according to one of claims 1 to 9, characterized in that the high-resistance electrical resistance (21 a, 21 b) by an FET, in particular a MOSFET is formed, with its source-drain path, the input terminal (1 5a , 1 5b) connects to the connection (22) for the common-mode reference potential and is applied with its gate to a control voltage.

1 1. microelectromechanical oscillator according to one of claims 1 to 1 0, characterized in that the control voltage is smaller than the threshold voltage of the MOSFET.

12. microelectromechanical oscillator according to one of claims 1 to 1 1, characterized in that they are for generating the control voltage a

Voltage source (23), the source output of which is connected to the gate of the MOSFET, and in that the voltage source (23) has a control input which is in control connection with the common-mode reference potential terminal (22). tion of the common mode reference potential, the electrical resistance of the source-drain path of the MOSFET remains substantially constant.

1 3. Microelectromechanical oscillator according to one of claims 1 to 1 2, characterized in that the capacitive sensor (9a, 9b) as a differential sensor with a non-inverting first measurement signal output and an inverting second measurement signal output and the operational amplifier (1 8) as a differential Operational amplifier (1 8) having a non-inverting first input terminal (1 5a), an inverting second input terminal (1 5b), a non-inverting first output terminal (20a), and an inverting second output terminal (20b). tet is that the first measuring signal output to the first input terminal (1 5a) and the second measuring signal output to the second input terminal (1 5b) is connected, that the first output terminal (2Oa) via a first integration capacitor (19a) with the second input terminal (1 5b) and the second output terminal (20b) via a second integration capacitor (19b) with the first input terminal (1 5a) is fed back, and that the first input terminal (1 5a) via a high-resistance first resistor (21 a) and the second input terminal is connected to the common mode reference potential terminal (22) via a high resistance second resistor (21b).

14. Microelectromechanical oscillator according to one of claims 1 to 1 3, characterized in that the operational amplifier (1 8) in addition to the first input terminal (15a, 1 5b) a first non-inverting auxiliary input (24a) and in addition to the second input terminal (1 5b ) has a second inverting auxiliary input (24b), that the second output terminal (20b) with a non-inverting first low-pass input (2όa) of a low-pass filter (27) and the first output terminal (20a) with an inverting second low-pass input (26b) of the low-pass filter (27) and that a non-inverting first low-bass output (28a) is connected to the first auxiliary input (24a) and an inverting second low-pass output (28b) of the low-pass filter (27) is connected to the second auxiliary input (24b).

1 5. microelectromechanical oscillator according to one of claims 1 to 1 4, characterized in that the second output terminal (20b) via a first resistance element (25a) with the first low-pass input (26a) and the first output terminal (20a) via a second resistance element ( 25b) is connected to the second Tiefbasseingang (2όb), and that the first Tiefpasseingang (2όb) via a third resistance element (25c) to the second Tiefpasseingang (26b) is connected.

16. microelectromechanical oscillator according to one of claims 1 to 1 5, characterized in that the low pass (27) at least one span- voltage-controlled current source (32) whose output is connected to an integration input of a Miller integrator (36).

17. Microelectromechanical oscillator according to one of claims 1 to 16, characterized in that the first low-pass input (26 a) with a

Input of a first transconductor (38a) and the second low-pass input (2όb) is connected to an input of a second transconductor (38b), that the first low-pass output (28a) with an output of the first transconductor (38a) and the second low-pass output (28b) an output of the second transconductor (38b) is connected, and that the output of the second transconductor (38b) via a first egenegenkopplungszweig (39a) with a first negative feedback terminal (40a) of the first Transconductors (38a) and the output of the first Transconductors (38a) via a second kopegenkopplungszweig (39b) with a second egenegenkopp- connection (40b) of the second Transconductors (38b) is connected.