MICROELECTROMECHANICAL OSCILLATOR WITH INTERMITTENT DRIVE

TECHNICAL FIELD

[0001] The invention is in the field of oscillator circuits to generate timing reference signals from resonator devices, and particularly microelectromechanical (also referred to as MEMS) resonator devices.

BACKGROUND

[0002] There are many inventions described and illustrated herein. The inventions relate to microelectromechanical and/or nanoelectromechanical (collectively hereinafter "microelectromechanical") structures and devices/systems including the same; and more particularly, in one aspect, to oscillator systems employing micro electromechanical resonating structures, and methods to control and/or operate the same.

[0003] Microelectromechanical systems, for example, gyroscopes, oscillators, resonators and accelerometers, utilize micromachining techniques (such as lithographic and other precision fabrication techniques) to reduce mechanical components to a scale that is generally comparable to microelectronics. Microelectromechanical systems typically include a microelectromechanical structure fabricated from or on, for example, a silicon substrate using micromachining techniques.

[0004] Most electronic products, for example computers, cell-phones, cameras, CD players, and watches, require at least one highly accurate and stable timing reference to synchronize the circuitry. Timing references typically include a resonator that has at a characteristic frequency. Examples of resonators include quartz crystal resonators (crystals), surface acoustic wave (SAW) resonators, ceramic resonators, micro electromechanical (MEMS) resonators, etc. In order to obtain a usable timing reference signal from a resonator, many circuits have been designed to drive the resonator and produce an output signal. For example, the common Pierce oscillator. These circuits are variously referred to as oscillator circuits, drive circuits, resonator drivers, etc.

[0005] Oscillator circuits are generally designed for or optimized for a particular type of resonator. Oscillator circuits designed and used for crystal, SAW or ceramic resonators are not generally suitable for microelectromechanical resonators. For example, microelectromechanical resonators are small relative to other types of resonators and often have higher motional resistance, lower power handling limits and lower signal output. The oscillator circuits used for these resonators must take these characteristics into consideration, for example with higher gain, enhanced drive power control, and lower electrical noise.

[0006] Typically, microelectromechanical resonators are driven by a continuous sine wave, or by a continuous square wave that may be generated from a continuous sine wave. Figure 1 is a block diagram of a typical oscillator circuit 100 that includes a microelectromechanical resonator 108. The microelectromechanical resonator 108 is connected between a drive amplifier 102 and a sense amplifier 104. A microelectromechanical resonator drive circuit 106 receives the output of the sense amplifier 104, which is typically a sine wave as shown. The microelectromechanical resonator drive circuit 106 operates on the input signal to produce a drive signal. As shown, the typical drive signal is a continuous signal that is usually generated by modifying the amplitude of the input sine wave, or clipping the input sine wave to produce a square wave.

[0007] There are challenges associated with designing circuits to drive microelectromechanical resonators that are not associated with designing circuits to drive other types of resonators. For microelectromechanical resonators that have relatively low frequencies compared to other microelectromechanical resonators, particular challenges apply. One reason for this is that lower frequency microelectromechanical resonators are often more susceptible to non-linearities and cannot be driven at the power levels that managed by higher frequency counterparts. The lower frequency microelectromechanical resonators become saturated, experience poor frequency consistency, respond non-linearly, and may even respond chaotically when power input is excessive.

[0008] The distinction between low and high frequency micro electromechanical resonators is gradual and not always distinct. While these undesirable

characteristics are often most prevalent in low frequency resonators, even higher frequency resonators can exhibit some of these in some applications. Therefore the applicability of this discussion to low frequency resonators should not be read to be limiting.

[0009] One way to achieve lower power input is to decrease the drive signal amplitude. However, merely decreasing the drive signal amplitude is sometimes difficult to do electronically. For example, the drive signal amplitude may be reduced by using a divider circuit to divide the amplitude by some factor, for example by ten. However, this increases the effective resonator impedance by the same factor, as seen by the oscillator circuit. An increase in the impedance of the resonator must be compensated for by an increase in the gain of the oscillator circuit. For example, in most electronics technologies, including complementary metal oxide semiconductor (CMOS) technologies, there is a normally a linear relationship of gain to power consumption, such that to increase the gain by a factor requires a proportional increase power consumption. Increased power consumption is undesirable in many microelectromechanical resonator applications. In power conserving applications such as wrist watches, etc., minimizing power consumption is often a high priority.

[0010] An alternative to pre-dividing the amplitude in order to decrease the power to the microelectromechanical resonator is to make an oscillator circuit that has a lower drive amplitude. The difficulty with this is that as the drive amplitude is made lower it often becomes more difficult to control. Another factor that complicates this approach that in order to save power in CMOS, the circuitry is biased in the subthreshold region. This is very power conservative, but has the side affect of making gain and amplitude control difficult, so that maintaining a specification over temperature, and over process, etc can be challenging or impractical.

[0011] There is a need for an oscillator drive circuit that can drive a microelectromechanical resonator lightly as required. There is further a need for such an oscillator that can deliver the required drive signal predictably and over process and temperature variations. The oscillator drive circuit should be capable of being built with common circuit fabrication technologies, like CMOS, should not be overly complex, and should operate in common application environments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a block diagram of a prior art oscillator circuit that includes a microelectromechanical resonator.

[0013] Figure 2 is a block diagram of an oscillator circuit according to an embodiment.

[0014] Figure 3 is a block diagram of an oscillator circuit according to another embodiment.

[0015] Figure 4 is a block diagram of an oscillator circuit according to another embodiment.

[0016] Figure 5 is a block diagram of an oscillator circuit according to another embodiment.

[0017] Figure 6 is a block diagram of an oscillator circuit according to another embodiment.

[0018] Figure 7 is a block diagram of an MRD controller according to an embodiment.

[0019] Figure 8 is a block diagram of an MRD controller according to another embodiment.

[0020] Figure 9 is a block diagram of an MRD controller according to another embodiment.

[0021] Figure 10 is a block diagram of an MRD controller according to another embodiment.

[0022] Figure 11 is a block diagram of an MRD controller according to another embodiment.

[0023] Figure 12 is a block diagram of an MRD controller according to another embodiment.

[0024] Figure 13 is a block diagram of an MRD controller according to another embodiment.

[0025] Figure 14 is a block diagram of an MRD controller according to another embodiment.

[0026] Figure 15 is a block diagram of a timing signal generating system according to an embodiment.

[0027] Figure 16 is a block diagram of a timing signal generating system according to another embodiment.

[0028] Figure 17 is a block diagram of a timing signal generating system according to another embodiment.

[0029] Figure 18 is a block diagram of a timing signal generating system according to another embodiment.

[0030] Figure 19 is a block diagram of elements of a timing signal generating system according to an embodiment.

[0031] Figure 20 is a block diagram of elements of a timing signal generating system according to another embodiment.

[0032] Figure 21 is a block diagram of elements of a timing signal generation system according to an embodiment.

[0033] Figure 22 is a block diagram of elements of a timing signal generation system according to another embodiment.

[0034] Figure 23 is a block diagram of elements of a timing signal generation system according to another embodiment.

[0035] Figure 24 is a block diagram of elements of a timing signal generation system according to another embodiment.

[0036] Figure 25 is a flow diagram illustrating a method of operating of a timing signal generating system according to an embodiment.

[0037] Figure 26 is a flow diagram illustrating a method of operating of a timing signal generating system according to another embodiment.

[0038] In the drawings, the same reference numbers identify identical or substantially similar elements or acts. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced (e.g., element 102 is first introduced and discussed with respect to Figure 1). The drawings illustrate particular embodiments for the purpose of describing the claimed invention, and are not intended to be exclusive or limiting in any way.

DETAILED DESCRIPTION

[0039] Embodiments of an oscillator circuit that can drive a microelectromechanical resonator are described herein. Embodiments include an oscillator circuit that drives the microelectromechanical resonator lightly (with low drive amplitude) as required

[0040] Embodiment of the oscillator drive circuit can be built with common circuit fabrication technologies, like CMOS, are not overly complex, and can operate in common application environments.

[0041] In various embodiments, the oscillator circuit drives a microelectromechanical resonator intermittently. As used herein, intermittently means that the drive signal is stopped altogether on some basis, before being started again.

[0042] Figure 2 is a block diagram of an oscillator circuit 200 according to an embodiment. The oscillator circuit 200 includes a microelectromechanical resonator 208 and a microelectromechanical resonator drive (MRD) controller 201. The MRD controller receives the output of the microelectromechanical resonator 208. In various embodiments, the output of the microelectromechanical resonator 208 is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator 208.

[0043] The MRD controller 201 includes circuitry to process the received signal and generate an appropriate drive signal to keep the microelectromechanical resonator 208 resonating and to satisfy the oscillator criteria for the circuit 200. In various embodiments as described below, the intermittently generated drive signal from the MRD controller 201 may be applied to the microelectromechanical resonator 208 such that the output of the microelectromechanical resonator 208 is substantially uniform in amplitude. Also, in alternative embodiments, as described below, the intermittently generated drive signal from the MRD controller 201 may be applied to the microelectromechanical resonator 208 such that the output of the microelectromechanical resonator 208 is allowed to decay to, for example, Vz or ^λ A of

its maximum amplitude before the next intermittent drive signal is applied, but embodiments are not so limited.

[0044] The MRD controller 201 generates an intermittent drive signal from the output of the microelectromechanical resonator 208 that drives the microelectromechanical resonator to produce a continuous output waveform with an amplitude sufficient for a particular operation. For example, the output of the microelectromechanical resonator 208 may be applied to a clock alignment circuit or component (not shown) to produce a timing reference signal, but embodiments are not so limited.

[0045] In various embodiments, the MRD controller 201 may include one or more of an amplifier stage, a pulse generator, a pulse width controller, an amplitude clipper, a duty cycle controller and one or more of other known circuits not mentioned here.

[0046] As will be further described below, the MRD controller 201 , in various embodiments, generates an intermittent drive signal in that the signal is generated, stopped, and then generated again. For example, instead of reducing the amplitude of the continuous input signal by ten, the MRD controller 201 may drive the resonator one tenth of the time. The microelectromechanical resonator 208, and microelectromechanical resonators in general, have high Q factors, or "high Q". The Q factor or quality factor is a measure of the "quality" of a resonant system. Resonant systems respond to frequencies close to their natural frequency much more strongly than they respond to other frequencies. The Q factor indicates the amount of resistance to resonance in a system. Systems with a high Q resonate with a greater amplitude (at the resonant frequency) than systems with a low Q. It is possible to drive a resonator with a high Q infrequently, and it will keep resonating. The amplitude of the resonator will change a small amount, but not enough to affect performance in typical applications. Microelectromechanical resonators have a Q that is anywhere from 10K up to 200K, and are trending higher with development Embodiments of the invention take advantage of this characteristic to drive a microelectromechanical resonator intermittently to provide time averaged drive

amplitude to the microelectromechanical resonator, yet satisfy other process and circuit constraints.

[0047] Figure 3 is a block diagram of an oscillator circuit 300 according to an embodiment. The oscillator circuit 300 includes a microelectromechanical resonator 308 and an MRD controller 301. The microelectromechanical resonator 308 is differentially coupled to the MRD controller 301 via differential signal lines 304 and 306. The MRD controller 301 receives a continuous input signal from the microelectromechanical resonator 308. Throughout this description, the output of the microelectromechanical resonator is assumed to be a continuous waveform, such as one of the example waveforms shown in Figure 2. The MRD controller 301 generates an intermittent drive signal from the output of the microelectromechanical resonator 308 that drives the microelectromechanical resonator to produce a continuous output waveform with an amplitude sufficient for a particular operation. For example, the output of the microelectromechanical resonator 308 may be applied to a clock alignment circuit or component (not shown) to produce a timing reference signal, but embodiments are not so limited.

[0048] In various embodiments, the MRD controller 301 may include one or more of an amplifier stage, a pulse generator, a pulse width controller, an amplitude clipper, a duty cycle controller and one or more of other known circuits not mentioned here.

[0049] Any of the embodiments shown herein may be differentially coupled between some or all components. Any of the embodiments shown may generate a single-ended or double-ended (differential) output. In the remainder of the description, differential signaling will not be explicitly shown for simplicity of illustration.

[0050] Figure 4 is a block diagram of an oscillator circuit 400 according to an embodiment. The oscillator circuit 400 includes a low frequency microelectromechanical resonator 408 and a microelectromechanical resonator drive (MRD) controller 401. The MRD controller receives the output of the microelectromechanical resonator 408. In various embodiments, the output of the

microelectromechanical resonator 408 is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator 408 (see for example Figure 2).

[0051] The MRD controller 401 includes circuitry to process the received signal and generate an appropriate drive signal to keep the resonator 408 resonating and to satisfy the oscillator criteria for the circuit 400. The MRD controller 401 generates an intermittent drive signal from the output of the microelectromechanical resonator 408 that drives the microelectromechanical resonator to produce a continuous output waveform with an amplitude sufficient for a particular operation. For example, the output of the microelectromechanical resonator 408 may be applied to a clock alignment circuit or component (not shown) to produce a timing reference signal, but embodiments are not so limited.

[0052] In various embodiments, the MRD controller 401 may include one or more of an amplifier stage, a pulse generator, a pulse width controller, an amplitude clipper, a duty cycle controller and one or more of other known circuits not mentioned here.

[0053] As will be further described below, the MRD controller 401 , in various embodiments, generates an intermittent drive signal in that the signal is generated, stopped, and then generated again. For example, instead of reducing the amplitude of the continuous signal by ten, the MRD controller 401 may drive the resonator one tenth of the time.

[0054] The oscillator circuit 400 further includes an amplifier 402 coupled between the output of the microelectromechanical resonator 408 and the input of the MRD controller 401. In an embodiment, the amplifier is a sense amplifier as known in the art.

[0055] Figure 5 is a block diagram of an oscillator circuit 500 according to an embodiment. The oscillator circuit 500 includes a low frequency microelectromechanical resonator 508 and a microelectromechanical resonator drive (MRD) controller 501. The MRD controller receives the output of the microelectromechanical resonator 508. In various embodiments, the output of the

microelectromechanical resonator 508 is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator 508 (see for example Figure 2).

[0056] The MRD controller 501 includes circuitry to process the received signal and generate an appropriate drive signal to keep the resonator 508 resonating and to satisfy the oscillator criteria for the circuit 500. The MRD controller 501 generates an intermittent drive signal from the output of the microelectromechanical resonator 508 that drives the microelectromechanical resonator to produce a continuous output waveform with an amplitude sufficient for a particular operation. For example, the output of the microelectromechanical resonator 508 may be applied to a clock alignment circuit or component (not shown) to produce a timing reference signal, but embodiments are not so limited.

[0057] In various embodiments, the MRD controller 501 may include one or more of an amplifier stage, a pulse generator, a pulse width controller, an amplitude clipper, a duty cycle controller and one or more of other known circuits not mentioned here.

[0058] As will be further described below, the MRD controller 501 , in various embodiments, generates an intermittent drive signal in that the signal is generated, stopped, and then generated again. For example, instead of reducing the amplitude of the continuous input signal by ten, the MRD controller 501 may drive the resonator one tenth of the time.

[0059] The oscillator circuit 500 further includes an amplifier 502 coupled between the output of the microelectromechanical resonator 508 and the input of the MRD controller 501. In an embodiment, the amplifier 502 is a drive amplifier as known in the art. In an embodiment, the amplifier 502 is a limiting or gain controlled amplifier as known in the art. Other known amplifiers used as stages to drive a resonator, but not mentioned here, are intended to be included in the scope of the embodiments.

[0060] Figure 6 is a block diagram of an oscillator circuit 600 according to an embodiment. The oscillator circuit 600 includes a low frequency

microelectromechanical resonator 608 and a microelectromechanical resonator drive (MRD) controller 601. The MRD controller receives the output of the microelectromechanical resonator 608. In various embodiments, the output of the microelectromechanical resonator 608 is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator 608 (see for example Figure 2).

[0061] The MRD controller 601 includes circuitry to process the received signal and generate an appropriate drive signal to keep the resonator 608 resonating and to satisfy the oscillator criteria for the circuit 600. The MRD controller 601 generates an intermittent drive signal from the output of the microelectromechanical resonator 608 that drives the microelectromechanical resonator to produce a continuous output waveform with an amplitude sufficient for a particular operation. For example, the output of the microelectromechanical resonator 608 may be applied to a clock alignment circuit or component (not shown) to produce a timing reference signal, but embodiments are not so limited.

[0062] In various embodiments, the MRD controller 601 may include one or more of an amplifier stage, a pulse generator, a pulse width controller, an amplitude clipper, a duty cycle controller and one or more of other known circuits not mentioned here.

[0063] As will be further described below, the MRD controller 601 , in various embodiments, generates an intermittent drive signal in that the signal is generated, stopped, and then generated again. For example, instead of reducing the amplitude of the continuous input signal by ten, the MRD controller 601 may drive the resonator one tenth of the time.

[0064] The oscillator circuit 600 further includes an amplifier 602 coupled between the output of the MRD controller 601 and the input of the microelectromechanical resonator 608. In an embodiment, the amplifier 602 is a drive amplifier as known in the art. In an embodiment, the amplifier 602 is a limiting or gain controlled amplifier as known in the art. Other known amplifiers used as

stages to drive a resonator, but not mentioned here, are intended to be included in the scope of the embodiments.

[0065] The oscillator circuit 600 further includes an amplifier 604 coupled between the output of the microelectromechanical resonator 608 and the input of the MRD controller 601. In an embodiment, the amplifier 604 is a sense amplifier as known in the art, but embodiments are not so limited.

[0066] Figure 7 is a block diagram of an MRD controller according to an embodiment. The MRD controller 701 includes an amplitude controller and a pulse divider. The MRD controller 701 receives the output of a microelectromechanical resonator (not shown). In various embodiments, the output of the microelectromechanical resonator is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator (see for example Figure 2).

[0067] The amplitude controller clips the output of the MRD controller 701 to a square wave as shown. The pulse divider eliminates some of the pulses that would normally be generated by the signal input to the MRD controller 701 to produce the intermittent square wave shown. In this way, a drive signal is intermittently received by the microelectromechanical resonator.

[0068] One or more characteristics of the output waveform (for example time between pulse, amplitude and duty cycle) may be predetermined based on characteristics of the resonator. Accordingly, the amplitude controller and the pulse divider, in various embodiments, may be programmable or reprogrammable to produce various combinations of output waveform characteristics. In yet other embodiments, the various characteristics of the output waveform are automatically adjusted based on an output of the resonator which is fed back (not shown) to the MRD controller 701 , but embodiments are not so limited.

[0069] In one embodiment the output of the controller may be a function of signals derived from elsewhere in the system. For example the output may be a function of temperature, which may be measured elsewhere, but embodiments are not so limited.

[0070] Figure 8 is a block diagram of an MRD controller 801 according to an embodiment. The MRD controller 801 includes an amplitude controller and a pulse divider/pulse generator. The MRD controller 801 receives the output of a microelectromechanical resonator (not shown). In various embodiments, the output of the microelectromechanical resonator is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator (see for example Figure 2).

[0071] The amplitude controller clips the output of the MRD controller 801 to a square wave as shown. The pulse divider eliminates some of the pulses that would normally be generated by the signal input to the MRD controller 801. The pulse generator can be used to insert pulses in some predetermined or randomized manner such to produce the irregular intermittent square wave shown. In this way, a drive signal is irregularly and intermittently received by the microelectromechanical resonator.

[0072] One or more characteristics of the output waveform (for example time between pulses, amplitude and duty cycle) may be predetermined based on characteristics of the resonator. Accordingly, the amplitude controller and the pulse divider/pulse generator, in various embodiments, may be programmable or reprogrammable to produce various combinations of output waveform characteristics. In yet other embodiments, the various characteristics of the output waveform are automatically adjusted based on an output of the resonator which is fed back (not shown) to the MRD controller 801 , but embodiments are not so limited.

[0073] In one embodiment the output of the controller may be a function of signals derived from elsewhere in the system. For example the output may be a function of temperature, which may be measured elsewhere, but embodiments are not so limited.

[0074] The randomization can be tailored to spread the noise in the drive signal or to minimize frequency content in one or more frequency bands. In this way potential or real interference from the intermittent drive on other circuitry or on the

resonator can be reduced, minimized or eliminated. The spreading function can be optimized by predetermined or measured data as needed.

[0075] Figure 9 is a block diagram of an MRD controller according to an embodiment. The MRD controller 901 includes an amplitude controller and a pulse generator. The MRD controller 901 receives the output of a microelectromechanical resonator (not shown). In various embodiments, the output of the microelectromechanical resonator is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator (see for example Figure 2).

[0076] The amplitude controller clips the output of the MRD controller 901 to a square wave as shown. The pulse generator generates relatively narrow pulses that are significantly shorter in duration than the pulses of the waveform input to the MRD controller 901. In various embodiments, the pulse generator may include a type of pulse width controller, or other circuits to produce a narrow pulse. In this way, a narrow drive signal is intermittently received by the microelectromechanical resonator, which results in lower effective output amplitude than, for example, a continuous square wave that is not pulse width limited.

[0077] One or more characteristics of the output waveform (for example pulse width, amplitude and duty cycle) may be predetermined based on characteristics of the resonator. Accordingly, the amplitude controller and the pulse generator, in various embodiments, may be programmable or reprogrammable to produce various combinations of output waveform characteristics. In yet other embodiments, the various characteristics of the output waveform are automatically adjusted based on an output of the resonator which is fed back (not shown) to the MRD controller 901 , but embodiments are not so limited.

[0078] In one embodiment the output of the controller may be a function of signals derived from elsewhere in the system. For example the output may be a function of temperature, which may be measured elsewhere, but embodiments are not so limited.

[0079] Figure 10 is a block diagram of an MRD controller 1001 according to an embodiment. The MRD controller 1001 includes an amplitude controller and a pulse generator. The MRD controller 1001 receives the output of a microelectromechanical resonator (not shown). In various embodiments, the output of the microelectromechanical resonator is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator (see for example Figure 2).

[0080] The amplitude controller clips the output of the MRD controller 1001 to a square wave as shown. The pulse generator generates relatively wide pulses compared to the pulses of the waveform input to the MRD controller 1001. In various embodiments, the pulse generator may include a type of pulse width controller, or other circuits to produce a wide pulse. In this way, a wide drive signal is intermittently received by the microelectromechanical resonator, which results in less effective drive amplitude than, for example, a continuous square wave that is of similar physical amplitude.

[0081] One or more characteristics of the output waveform (for example pulse width, amplitude and duty cycle) may be predetermined based on characteristics of the resonator. Accordingly, the amplitude controller and the pulse generator, in various embodiments, may be programmable or reprogrammable to produce various combinations of output waveform characteristics. In yet other embodiments, the various characteristics of the output waveform are automatically adjusted based on an output of the resonator which is fed back (not shown) to the MRD controller 1001 , but embodiments are not so limited.

[0082] In one embodiment the output of the controller may be a function of signals derived from elsewhere in the system. For example the output may be a function of temperature, which may be measured elsewhere, but embodiments are not so limited.

[0083] Figure 11 is a block diagram of an MRD controller 1101 according to an embodiment. The MRD controller 1101 includes an amplitude controller, a pulse divider, and a polarity controller. The MRD controller 1101 receives the output of a

microelectromechanical resonator (not shown). In various embodiments, the output of the microelectromechanical resonator is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the micro electromechanical resonator (see for example Figure 2).

[0084] The amplitude controller clips the output of the MRD controller 1101 to a square wave as shown. The pulse generator, with the polarity controller, generates pulses of alternating polarities, as shown. In various embodiments, the pulse generator may include a type of pulse width controller, or other circuits to produce a pulse. In this way, a drive signal that is sometimes adding power and sometimes subtracting power is intermittently received by the microelectromechanical resonator, which results in less average power input than, for example, a continuous square wave.

[0085] The alternating pulse polarity can be used to provide less average drive. With variations in waveform timing, it can be configured to be purely additive in drive or partially additive and partially subtractive. Even in the additive case, the bipolar drive as benefits, for instance that the average DC component can be zero.

[0086] One or more characteristics of the output waveform (for example pulse width, amplitude and duty cycle) may be predetermined based on characteristics of the resonator. Accordingly, the amplitude controller and the pulse generator, in various embodiments, may be programmable or reprogrammable to produce various combinations of output waveform characteristics. In yet other embodiments, the various characteristics of the output waveform are automatically adjusted based on an output of the resonator which is fed back (not shown) to the MRD controller 1101 , but embodiments are not so limited.

[0087] In one embodiment the output of the controller may be a function of signals derived from elsewhere in the system. For example the output may be a function of temperature, which may be measured elsewhere, but embodiments are not so limited.

[0088] Figure 12 is a block diagram of an MRD controller according to an embodiment. The MRD controller 1201 includes an amplitude controller, a pulse

divider, and a polarity controller. The MRD controller 1201 receives the output of a microelectromechanical resonator (not shown). In various embodiments, the output of the microelectromechanical resonator is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator (see for example Figure 2).

[0089] The amplitude controller clips the output of the MRD controller 1201 to a square wave as shown. The pulse generator, with the polarity controller, generates relatively narrow (compared to the output of the resonator) pulses of alternating polarities, as shown. In various embodiments, the pulse generator may include a type of pulse width controller, or other circuits to produce a pulse. In this way, a drive signal that is sometimes adding power and sometimes subtracting power, is intermittently received by the microelectromechanical resonator, which results in less average drive than, for example, a continuous square wave.

[0090] One or more characteristics of the output waveform (for example pulse width, amplitude and duty cycle) may be predetermined based on characteristics of the resonator. Accordingly, the amplitude controller and the pulse generator, in various embodiments, may be programmable or reprogrammable to produce various combinations of output waveform characteristics. In yet other embodiments, the various characteristics of the output waveform are automatically adjusted based on an output of the resonator which is fed back (not shown) to the MRD controller 1201 , but embodiments are not so limited.

[0091] The alternating pulse polarity can be used to provide less average drive. With variations in waveform timing, it can be configured to be purely additive in drive or partially additive and partially subtractive. Even in the additive case, the bipolar drive as benefits, for instance that the average DC component can be zero.

[0092] Figure 13 is a block diagram of an MRD controller 1301 according to an embodiment. The MRD controller 1301 includes a drive trigger. The MRD controller 1301 receives the output of a microelectromechanical resonator (not shown). In various embodiments, the output of the microelectromechanical resonator is a sine

wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator (see for example Figure 2).

[0093] The drive trigger drives the microelectromechanical resonator intermittently with a sine wave as shown. In an embodiment the MRD controller 1301 drives the microelectromechanical resonator at predetermined intervals, which results in less power input than, for example, a continuous sine wave or a continuous square wave.

[0094] The interval at which to drive the microelectromechanical resonator may be predetermined based on characteristics of the resonator. Accordingly, the amplitude controller and the pulse generator, in various embodiments, may be programmable or reprogrammable to produce various combinations of output waveform characteristics, for example, driving at regular or irregular intervals. In yet other embodiments, drive intervals are automatically adjusted based on an output of the resonator which is fed back (not shown) to the MRD controller 1301 , but embodiments are not so limited.

[0095] In one embodiment the output of the controller may be a function of signals derived from elsewhere in the system. For example the output may be a function of temperature, which may be measured elsewhere, but embodiments are not so limited.

[0096] Figure 14 is a block diagram of an MRD controller 1401 according to an embodiment. The MRD controller 1401 includes a resonator amplitude monitor and a pulse generator. The MRD controller 1401 receives the output of a microelectromechanical resonator (not shown). In various embodiments, the output of the microelectromechanical resonator is a sine wave, a square wave, a triangle wave, or some other continuous waveform generated by the microelectromechanical resonator (see for example Figure 2). A sine wave is shown at the input of the MRD controller 1401 , which is allowed to decay, or ring down between drive pulses.

[0097] The drive trigger drives the microelectromechanical resonator intermittently with a pulse as shown. The drive interval is such that the resonator partial rings down between drive pulses. The arrows connecting drive pulses and the

input waveform show how an output pulse cause the resonator to output a sine wave, which is then allowed to decay.

[0098] In an embodiment the MRD controller 1401 drives the microelectromechanical resonator at intervals based monitoring the resonator sine wave, for example generating a driving pulse when the microelectromechanical resonator sine wave is below a predetermined amplitude. In other embodiments, the drive interval is predetermined based on known characteristics of the microelectromechanical resonator.

[0099] The preceding description of the drive pulse should not be understood to be limited to a single pulse. It may be a pulse string or sequence, or a set of bipolar pulses, or a modulated drive signal as previously described. It may be a waveform not yet described.

[0100] Accordingly, the amplitude controller and the pulse generator, in various embodiments, may be programmable or reprogrammable to produce various regular or irregular drive intervals. In embodiments in which drive intervals are automatically adjusted based on an output of the resonator which is fed back (not shown) to the MRD controller 1401 resonator amplitude monitor, the predetermined sine wave amplitude may be programmed, but embodiments are not so limited.

[0101] In one embodiment the output of the controller may be a function of signals derived from elsewhere in the system. For example the output may be a function of temperature, which may be measured elsewhere, but embodiments are not so limited.

[0102] Figure 15 is a block diagram of a timing signal generating system 1500 according to an embodiment. The system 1500 includes a microelectromechanical resonator 1508 and timing signal generation and control circuitry 1510. The circuitry 1510 includes an MRD controller 1501 coupled to clock alignment circuitry 1502. The clock alignment circuitry may include, for example, one or more phase locked loops (PLLs), delay locked loops (DLLs), digital/frequency synthesizer, for example, a direct digital synthesizer ("DDS"), frequency synthesizer, fractional synthesizer and/or numerically controlled oscillator, and/or frequency locked loops (FLLs)) to

adjust (for example, increase or decrease) and/or control the frequency of the output signal of the timing signal generating system 1500. In this way, a resulting clock signal may include a predetermined frequency that is higher or lower in frequency than the frequency of the output signal of the microelectromechanical resonator 1508. Indeed, the clock alignment circuitry may provide a plurality of output signals that are higher and/or lower in frequency than the frequency of the output signal of the microelectromechanical resonator 1508.

[0103] The MRD controller 1501 includes any embodiments as described herein and other embodiments not specifically described but within the scope and spirit of the embodiments as claimed.

[0104] A control circuit 1504 is coupled to the MRD controller 1501 and to the clock alignment circuitry 1502. The control circuit 1504 may alternatively be connected to only the MRD controller 1501 or only to the clock alignment circuitry 1502. The control circuit 1504 may be any one of a variety of known controllers, including a state machine, a microprocessor, or any of a wide variety of circuits that can supply a control output. The control circuit may include memory devices, including but not limited to, read only memory (ROM), random access memory (RAM), reprogrammable PROM, electrically erasable programmable ROM (EEPROM), one-time programmable ROM (OTPROM), fuse or antifuse OTPROM, etc. The control circuitry 1504, in an embodiment, manages and may store configuration information for the MRD controller 1501 and the clock alignment circuitry 1502. For example, configuration information may include data to determine characteristics of the drive signal output by the MRD controller 1501 as described above. The configuration information may also include characteristics of the microelectromechanical resonator 1508 and/or particular values of one or more of the characteristics to be references for control purposes, as previously described. The controller circuit 1504 may include one or more sensors, for instance a temperature sensor, which may be used in controlling the MRD Controller 1501 and/or the Clock Alignment circuitry 1502.

[0105] An interface 1506 may be coupled to the control circuit 1504 for inputting information, including for instance configuration information as described above, and

for outputting information, including for instance status information or history information. In an embodiment, the interface 1506 is a serial interface, but the embodiment is not so limited. In some cases the interface may be omitted.

[0106] Figure 16 is a block diagram of a timing signal generating system 1600 according to an embodiment. The system 1600 includes a microelectromechanical resonator 1608 and timing signal generation and control circuitry 1610, including an MRD controller 1601 and a control circuit 1604. The control circuitry 1610 may include other components or circuits, not shown here for simplicity.

[0107] The microelectromechanical resonator 1608, and all microelectromechanical resonators described herein, may employ any type of microelectromechanical resonator design, whether now known or later developed; and all such microelectromechanical resonator designs and architectures are intended to fall within the scope of the embodiments described and claimed. For example, the microelectromechanical resonator 1608 may include one or more resonating beams which are anchored at one ends. Moreover, the microelectromechanical resonator 1608 may include a paddle-like design. Indeed, the microelectromechanical resonator 1608 may be a component or portion of the same physical structure and/or the microelectromechanical resonator 1608 may be the same component or portion of the same physical structure that resonate in multiple, different modes of operation, for example, in-plane and out-of-plane or at various crystallographic angles. Again, all microelectromechanical resonator designs, structures and techniques, whether now known or later developed, are intended to fall within the scope of the present embodiments.

[0108] In an embodiment, as shown, the microelectromechanical resonator 1608 is disposed on/in a different substrate than timing signal generation and control circuitry 1610.

[0109] In addition, microelectromechanical resonator 1608 and timing signal generation and control circuitry 1610 may be fabricated, in whole or in part, in/from the same materials or different materials. For example, microelectromechanical resonator 1608 and timing signal generation and control circuitry 1610 may be

integrated on/in different substrates of different materials, including monocrystalline silicon and polycrystalline silicon. Further, microelectromechanical resonator 1608 and timing signal generation and control circuitry 1610 may be integrated on/in different substrates of the same materials, including monocrystalline silicon and polycrystalline silicon. Moreover, MRD controller 1601 and control circuitry 1610, and microelectromechanical resonator 1608 may also be fabricated in/from the same or different materials. All permutations and combinations thereof are intended to fall within the scope of the present embodiments.

[0110] Further, MRD controller 1601 and control circuitry 1610, and microelectromechanical resonator 1608 may be fabricated and/or packaged using any fabrication and/or packaging techniques whether now known or later developed. Indeed, all such fabrication and/or packaging techniques are intended to fall within the scope of the present embodiments.

[0111] The output signal of system 1600 may be single ended or double ended (that is differential signaling). The "shape" of the output signal (for example, square, pulse, sinusoidal or clipped sinusoidal) may be predetermined and/or programmable. In this regard, information which is representative of the "shape" of the output signal may be stored or programmed in memory during fabrication, test, calibration and/or operation. The memory may be resident in the control circuit 1604, for example, but embodiments are not so limited. In this way, the control circuit 1604 (and/or clock alignment circuitry (if any)) may access a resident memory to obtain such information during start-up/power-up, initialization, re-initialization and/or during normal operation of the system 1600.

[0112] In those instances where various referenced elements of the system 1600 are fabricated in/on separate substrates, the various signals may be provided using electrical interconnects (not illustrated) connecting bond pads (not illustrated) located in/on substrates and/or flip-chip techniques. Where various referenced elements of the system 1600 are fabricated in/on the same substrate, the various signals may be provided using interconnections disposed in/on the substrates. The described embodiments may employ any interconnect or interconnection technique/architecture whether now known (for example, wire bonding) or later

developed. All such techniques/architectures are intended to fall within the scope of the present embodiments.

[0113] The timing signal generating system 1600 may be formed into one assembly, for instance a plastic chip. Alternately they may be two or more individual components. The single or multiple components may be further formed or integrated into a larger component. For example, the timing signal generating system may be integrated into (that is, a part of) a radio frequency transceiver chip, where it might for example provide an RF reference frequency. All such levels of integration are intended to fall within the scope of the present embodiments.

[0114] Figure 17 is a block diagram of a timing signal generating system 1700 according to an embodiment. The system 1700 includes a microelectromechanical resonator 1708 and timing signal generation and control circuitry 1710, including an MRD controller 1701 and a control circuit 1704. The control circuitry 1710 may include other components or circuits, not shown here for simplicity.

[0115] The microelectromechanical resonator 1708, and all microelectromechanical resonators described herein, may employ any type of microelectromechanical resonator design, whether now known or later developed; and all such microelectromechanical resonator designs and architectures are intended to fall within the scope of the embodiments described and claimed. For example, the microelectromechanical resonator 1708 may include one or more resonating beams which are anchored at one end. Moreover, the microelectromechanical resonator 1708 may include a paddle-like design. Indeed, the microelectromechanical resonator 1708 may be a component or portion of the same physical structure and/or the microelectromechanical resonator 1708 may be the same component or portion of the same physical structure that resonate in multiple, different modes of operation, for example, in-plane and out-of-plane or at various crystallographic angles. Again, all microelectromechanical resonator designs, structures and techniques, whether now known or later developed, are intended to fall within the scope of the present embodiments.

[0116] In an embodiment, as shown, the microelectromechanical resonator 1708 is disposed on/in the same substrate as control circuitry 1710.

[0117] The microelectromechanical resonator 1708 and control circuitry 1710 may be fabricated, in whole or in part, in/from the same materials or different materials. For example, microelectromechanical resonator 1708 and control circuitry 1710 may be integrated on/in the same substrates of the same materials, including monocrystalline silicon and polycrystalline silicon. Moreover, MRD controller 1701 and control circuitry 1710, and micro electromechanical resonator 1708 may also be fabricated in/from the same or different materials. All permutations and combinations thereof are intended to fall within the scope of the present embodiments.

[0118] Further, MRD controller 1701 and control circuit 1704, and microelectromechanical resonator 1708 may be fabricated and/or packaged using any fabrication and/or packaging techniques whether now known or later developed. Indeed, all such fabrication and/or packaging techniques are intended to fall within the scope of the present embodiments.

[0119] The output signal of system 1700 may be single ended or double ended (that is differential signaling). The "shape" of the output signal (for example, square, pulse, sinusoidal or clipped sinusoidal) may be predetermined and/or programmable. In this regard, information which is representative of the "shape" of the output signal may be stored or programmed in memory during fabrication, test, calibration and/or operation. The memory may be resident in the control circuit 1704, for example, but embodiments are not so limited. In this way, the control circuit 1704 (and/or clock alignment circuitry (if any)) may access a resident memory to obtain such information during start-up/power-up, initialization, re-initialization and/or during normal operation of the system 1700.

[0120] In those instances where various referenced elements of the system 1700 are fabricated in/on separate substrates, the various signals may be provided using electrical interconnects (not illustrated) connecting bond pads (not illustrated) located in/on substrates and/or flip-chip techniques. Where various referenced elements of the system 1700 are fabricated in/on the same substrate, the various

signals may be provided using interconnections disposed in/on the substrates. The described embodiments may employ any interconnect or interconnection technique/architecture whether now known (for example, wire bonding) or later developed. All such techniques/architectures are intended to fall within the scope of the present embodiments.

[0121] The timing signal generating system 1600 may be formed into one assembly, for instance a plastic chip. Alternately they may be two or more individual components. The single or multiple components may be further formed or integrated into a larger component. For example, the timing signal generating system may be integrated into (that is, a part of) a radio frequency transceiver chip, where it might for example provide an RF reference frequency. All such levels of integration are intended to fall within the scope of the present embodiments.

[0122] Figure 18 is a block diagram of a timing signal generating system 1800 according to an embodiment. The system 1800 includes a microelectromechanical resonator 1808, and MRD controller 1801 , and a control circuit 1804.

[0123] The microelectromechanical resonator 1808, and all microelectromechanical resonators described herein, may employ any type of microelectromechanical resonator design, whether now known or later developed; and all such microelectromechanical resonator designs and architectures are intended to fall within the scope of the embodiments described and claimed. For example, the microelectromechanical resonator 1808 may include a resonating beam which is anchored at both ends. Moreover, the microelectromechanical resonator 1808 may include a paddle-like design. Indeed, the microelectromechanical resonator 1808 may be a component or portion of the same physical structure and/or the microelectromechanical resonator 1808 may be the same component or portion of the same physical structure that resonate in multiple, different modes of operation, for example, in-plane and out-of-plane. Again, all microelectromechanical resonator designs, structures and techniques, whether now known or later developed, are intended to fall within the scope of the present embodiments.

[0124] In an embodiment, as shown, the microelectromechanical resonator 1808 is disposed on/in the same substrate the MRD controller 1801 , while the control circuit 1804 is disposed on/in a different substrate.

[0125] The microelectromechanical resonator 1808 and the MRD controller 1801 may be fabricated, in whole or in part, in/from the same materials or different materials. For example, microelectromechanical resonator 1808 and timing signal generation and control circuit 1804 may be integrated on/in the same substrates of the same materials, including monocrystalline silicon and polycrystalline silicon. Moreover, the microelectromechanical resonator 1808 and the MRD controller 1801 may also be fabricated in/from the different materials. In addition, the microelectromechanical resonator 1808 and the MRD controller 1801 may be fabricated in/from the same materials, while the control circuit 1804 is fabricated in/from either the same or different materials. All permutations and combinations thereof are intended to fall within the scope of the present embodiments.

[0126] Further, the resonator 1808, the MRD controller 1801 , and the control circuit 1804 may be fabricated and/or packaged using any fabrication and/or packaging techniques whether now known or later developed. Indeed, all such fabrication and/or packaging techniques are intended to fall within the scope of the present embodiments.

[0127] The output signal of system 1800 may be single ended or double ended (that is differential signaling). The "shape" of the output signal (for example, square, pulse, sinusoidal or clipped sinusoidal) may be predetermined and/or programmable. In this regard, information which is representative of the "shape" of the output signal may be stored or programmed in memory during fabrication, test, calibration and/or operation. The memory may be resident in the control circuit 1804, for example, but embodiments are not so limited. In this way, the control circuit 1804 (and/or clock alignment circuitry (if any)) may access a resident memory to obtain such information during start-up/power-up, initialization, re-initialization and/or during normal operation of the system 1800.

[0128] In those instances where various referenced elements of the system 1800 are fabricated in/on separate substrates, the various signals may be provided using electrical interconnects (not illustrated) connecting bond pads (not illustrated) located in/on substrates and/or flip-chip techniques. Where various referenced elements of the system 1800 are fabricated in/on the same substrate, the various signals may be provided using interconnections disposed in/on the substrates. The described embodiments may employ any interconnect or interconnection technique/architecture whether now known (for example, wire bonding) or later developed. All such techniques/architectures are intended to fall within the scope of the present embodiments.

[0129] The timing signal generating system 1700 may be integrated into and packaged with a larger system, or may be integrated into a larger system buy packaged separately. All such integration levels are intended to fall within the present embodiment.

[0130] Figure 19 is a block diagram of elements of a timing signal generating system 1900 according to an embodiment. The system 1900 includes two microelectromechanical resonators, 1908A and 1908B, an MRD controller 1901 and a control circuit 1904. The control circuit 1904 may include other components or circuits, not shown here for simplicity.

[0131] Multiple microelectromechanical resonators are useful in timing signal generating systems to provide accurate timing signals in the presence of temperature change, for example. The behavior of each microelectromechanical resonator in the presence of temperature change, along with the known characteristics of each microelectromechanical resonator may be used to accurately determine frequency as a function of temperature.

[0132] In embodiment, the system 1900 may be configured to provide and/or generate one or more output signals having a predetermined frequency over temperature, for example, (1) an output signal having a substantially stable frequency (i.e., constant, substantially constant and/or essentially constant frequency) of over a predetermined range of operating temperatures, (2) an output

signal having a frequency that is dependent on the operating temperature from which the operating temperature may be determined (for example, an estimated operating temperature based on empirical data and/or a mathematical relationship), and/or (3) an output signal that is relatively stable over a range of temperatures (for example, a predetermined operating temperature range) and is "shaped" to have a desired turn-over frequency.

[0133] The microelectromechanical resonators 1908, and all microelectromechanical resonators described herein, may employ any type of microelectromechanical resonator design, whether now known or later developed; and all such microelectromechanical resonator designs and architectures are intended to fall within the scope of the embodiments described and claimed. For example, one or both of the microelectromechanical resonators 1908 may include a resonating beam which is anchored at one or both ends. Moreover, one or both of the microelectromechanical resonators 1908 may include a paddle-like design. Indeed, the microelectromechanical resonators 1908 may each be a component or portion of the same physical structure and/or the same component or portion of the same physical structure that resonates in multiple, different modes of operation, for example, in-plane and out-of-plane. Again, all microelectromechanical resonator designs, structures and techniques, whether now known or later developed, are intended to fall within the scope of the present embodiments.

[0134] In the system 1900, each of the microelectromechanical resonators 1908 is coupled to the MRD controller 1901 , which controls them both, but embodiments are not so limited. In other embodiments, more than two microelectromechanical resonators 1908 can be used and controller by the MRD controller 1901.

[0135] Figure 20 is a block diagram of elements of a timing signal generating system 2000 according to an embodiment. The system 2000 includes two microelectromechanical resonators, 2008A and 2008B. The microelectromechanical resonators 2008A is controlled by an MRD controller 2001 A, and the microelectromechanical resonators 2008B is controlled by an MRD controller 2001 B. MRD controllers 2001 are each coupled to a control circuit 2004. The control circuit 2004 may include other components or circuits, not shown here for simplicity.

[0136] Figure 21 is a block diagram of elements of a timing signal generation system 2100 according to an embodiment. The system 2100 includes two microelectromechanical resonators, 2108A and 2108B, one or more MRD controllers 2101 , and a control circuit 2104, all of which are disposed in/on the same substrate, but embodiments are not so limited.

[0137] Further, microelectromechanical resonators 2108, and MRD controllers 2101 and a control circuit 2104 may be fabricated and/or packaged using any fabrication and/or packaging techniques whether now known or later developed. Indeed, all such fabrication and/or packaging techniques are intended to fall within the scope of the present embodiments.

[0138] The output signal of system 2100 may be single ended or double ended (that is differential signaling). The "shape" of the output signal (for example, square, pulse, sinusoidal or clipped sinusoidal) may be predetermined and/or programmable. In this regard, information which is representative of the "shape" of the output signal may be stored or programmed in memory during fabrication, test, calibration and/or operation. The memory may be resident in the control circuit 2104, for example, but embodiments are not so limited. In this way, the control circuit 2104 (and/or clock alignment circuitry (if any)) may access a resident memory to obtain such information during start-up/power-up, initialization, re-initialization and/or during normal operation of the system 2100.

[0139] In those instances where various referenced elements of the system 2100 are fabricated in/on separate substrates, the various signals may be provided using electrical interconnects (not illustrated) connecting bond pads (not illustrated) located in/on substrates and/or flip-chip techniques. Where various referenced elements of the system 2100 are fabricated in/on the same substrate, the various signals may be provided using interconnections disposed in/on the substrates. The described embodiments may employ any interconnect or interconnection technique/architecture whether now known (for example, wire bonding) or later developed. All such techniques/architectures are intended to fall within the scope of the present embodiments.

[0140] Figure 22 is a block diagram of elements of a timing signal generation system 2200 according to an embodiment. The system 2200 includes two microelectromechanical resonators, 2108A and 2108B disposed in/on one substrate. The system 2200 also includes one or more MRD controllers 2201 , and a control circuit 2204, both of which are disposed in/on the same substrate, but embodiments are not so limited.

[0141] In addition, microelectromechanical resonators 2208, and MRD controllers 2201 and a control circuit 2204 may be fabricated, in whole or in part, in/from the same materials or different materials. For example, microelectromechanical resonator 2208, and MRD controllers 2201 and control circuit 2204 may be integrated on/in different substrates of different materials, including monocrystalline silicon and polycrystalline silicon. Further microelectromechanical resonators 2208, and MRD controllers 2201 and control circuit 2204 may be integrated on/in different substrates of the same materials, including monocrystalline silicon and polycrystalline silicon. All permutations and combinations thereof are intended to fall within the scope of the present embodiments.

[0142] Further, microelectromechanical resonators 2208, and MRD controllers 2201 and control circuit 2204 may be fabricated and/or packaged using any fabrication and/or packaging techniques whether now known or later developed. Indeed, all such fabrication and/or packaging techniques are intended to fall within the scope of the present embodiments.

[0143] The output signal of system 2200 may be single ended or double ended (that is differential signaling). The "shape" of the output signal (for example, square, pulse, sinusoidal or clipped sinusoidal) may be predetermined and/or programmable. In this regard, information which is representative of the "shape" of the output signal may be stored or programmed in memory during fabrication, test, calibration and/or operation. The memory may be resident in the control circuit 2204, for example, but embodiments are not so limited. In this way, the control circuit 2204 (and/or clock alignment circuitry (if any)) may access a resident memory to obtain such information during start-up/power-up, initialization, re-initialization and/or during normal operation of the system 2200.

[0144] In those instances where various referenced elements of the system 2200 are fabricated in/on separate substrates, the various signals may be provided using electrical interconnects (not illustrated) connecting bond pads (not illustrated) located in/on substrates and/or flip-chip techniques. Where various referenced elements of the system 2200 are fabricated in/on the same substrate, the various signals may be provided using interconnections disposed in/on the substrates. The described embodiments may employ any interconnect or interconnection technique/architecture whether now known (for example, wire bonding) or later developed. All such techniques/architectures are intended to fall within the scope of the present embodiments.

[0145] Figure 23 is a block diagram of elements of a timing signal generation system 2300 according to an embodiment. The system 2300 includes two microelectromechanical resonators, 2108A and 2108B disposed in/on separate substrates. The system 2300 also includes one or more MRD controllers 2301 , and a control circuit 2304, both of which are disposed in/on the same substrate, but embodiments are not so limited.

[0146] In addition, microelectromechanical resonators 2308, and MRD controllers 2301 and control circuit 2304 may be fabricated, in whole or in part, in/from the same materials or different materials. For example, microelectromechanical resonator 2308, and MRD controllers 2301 and control circuit 2304 may be integrated on/in different substrates of different materials, including monocrystalline silicon and polycrystalline silicon. Further microelectromechanical resonators 2308, and MRD controllers 2301 and control circuit 2304 may be integrated on/in different substrates of the same materials, including monocrystalline silicon and polycrystalline silicon. All permutations and combinations thereof are intended to fall within the scope of the present embodiments.

[0147] Further, microelectromechanical resonators 2308, and MRD controllers 2301 and a control circuit 2304 may be fabricated and/or packaged using any fabrication and/or packaging techniques whether now known or later developed. Indeed, all such fabrication and/or packaging techniques are intended to fall within the scope of the present embodiments.

[0148] The output signal of system 2300 may be single ended or double ended (that is differential signaling). The "shape" of the output signal (for example, square, pulse, sinusoidal or clipped sinusoidal) may be predetermined and/or programmable. In this regard, information which is representative of the "shape" of the output signal may be stored or programmed in memory during fabrication, test, calibration and/or operation. The memory may be resident in the control circuit 2304, for example, but embodiments are not so limited. In this way, the control circuit 2304 (and/or clock alignment circuitry (if an)) may access a resident memory to obtain such information during start-up/power-up, initialization, re-initialization and/or during normal operation of the system 2300.

[0149] In those instances where various referenced elements of the system 2300 are fabricated in/on separate substrates, the various signals may be provided using electrical interconnects (not illustrated) connecting bond pads (not illustrated) located in/on substrates and/or flip-chip techniques. Where various referenced elements of the system 2300 are fabricated in/on the same substrate, the various signals may be provided using interconnections disposed in/on the substrates. The described embodiments may employ any interconnect or interconnection technique/architecture whether now known (for example, wire bonding) or later developed. All such techniques/architectures are intended to fall within the scope of the present embodiments.

[0150] Figure 24 is a block diagram of elements of a timing signal generation system 2400 according to an embodiment. The system 2400 includes two microelectromechanical resonators, 2108A and 2108B, and includes one or more MRD controllers 2401 , all disposed in/on the same substrate. The system 2400 also includes a control circuit 2404, which is disposed in/on a separate substrate, but embodiments are not so limited.

[0151] In addition, microelectromechanical resonators 2408, and MRD controllers 2401 and control circuit 2404 may be fabricated, in whole or in part, in/from the same materials or different materials. For example, microelectromechanical resonator 2408, and MRD controllers 2401 and control circuit 2404 may be integrated on/in different substrates of different materials, including monocrystalline

silicon and polycrystalline silicon. Further microelectromechanical resonators 2408, and MRD controllers 2401 and control circuit 2404 may be integrated on/in different substrates of the same materials, including monocrystalline silicon and polycrystalline silicon. All permutations and combinations thereof are intended to fall within the scope of the present embodiments.

[0152] Further, microelectromechanical resonators 2408, and MRD controllers 2401 and a control circuit 2404 may be fabricated and/or packaged using any fabrication and/or packaging techniques whether now known or later developed. Indeed, all such fabrication and/or packaging techniques are intended to fall within the scope of the present embodiments.

[0153] The output signal of system 2400 may be single ended or double ended (that is differential signaling). The "shape" of the output signal (for example, square, pulse, sinusoidal or clipped sinusoidal) may be predetermined and/or programmable. In this regard, information which is representative of the "shape" of the output signal may be stored or programmed in memory during fabrication, test, calibration and/or operation. The memory may be resident in the control circuit 2404, for example, but embodiments are not so limited. In this way, the control circuit 2404 (and/or clock alignment circuitry (if any)) may access a resident memory to obtain such information during start-up/power-up, initialization, re-initialization and/or during normal operation of the system 2400.

[0154] In those instances where various referenced elements of the system 2400 are fabricated in/on separate substrates, the various signals may be provided using electrical interconnects (not illustrated) connecting bond pads (not illustrated) located in/on substrates and/or flip-chip techniques. Where various referenced elements of the system 2400 are fabricated in/on the same substrate, the various signals may be provided using interconnections disposed in/on the substrates. The described embodiments may employ any interconnect or interconnection technique/architecture whether now known (for example, wire bonding) or later developed. All such techniques/architectures are intended to fall within the scope of the present embodiments.

[0155] The microelectromechanical resonators, MRD controllers and control circuits shown herein can be part of any system using the timing signal capabilities provided by the described embodiments. For example, some or all of the control functionality described with reference to the MRD controllers control circuits can be provided by a microprocessor in a system.

[0156] Figure 25 is a flow diagram illustrating a method 2500 of operating of a timing signal generating system according to an embodiment. For example, method 2500 is applicable to the system 1500 of Figure 15. At 2502, the timing signal generation and control circuitry (such as circuitry 1510, for example) is programmed based on known characteristics of a microelectromechanical resonator of the system (for example, resonator 1508). Programming in an embodiment includes programming the driving behavior of an MRD controller, such as the MRD controller 1501. The programming in some instances takes place during wafer fabrication such that the hardware is pre-programmed after fabrication, but embodiments are not so limited.

[0157] At 2504, the oscillator circuit is initialized. The oscillator circuit includes the elements as shown in Figures 2-14, for example, but embodiments are not so limited.

[0158] At 2506, the microelectromechanical resonator is driven according to the programmed driving behavior, including driving at predetermined intervals and with predetermined waveforms.

[0159] Figure 26 is a flow diagram illustrating a method 2600 of operating of a timing signal generating system according to an embodiment. For example, method 2600 is applicable to the system 1500 of Figure 15. At 2602, the timing signal generation and control circuitry (such as circuitry 1510, for example) is programmed based on known characteristics of a microelectromechanical resonator of the system (for example, resonator 1508). Programming in an embodiment includes programming the driving behavior of an MRD controller, such as the MRD controller 1501. Programming further includes programming monitoring behavior for monitoring the output of the microelectromechanical resonator under control. The

programming in some instances takes place during wafer fabrication such that the hardware is pre-programmed, but embodiments are not so limited.

[0160] At 2604, the oscillator circuit is initialized, including setting initial drive parameters. The oscillator circuit includes the elements as shown in Figures 2-14, for example, but embodiments are not so limited.

[0161] At 2606, the microelectromechanical resonator is driven according to the programmed initial driving behavior, including driving with a predetermined initial waveform.

[0162] At 2608 the output of the microelectromechanical resonator occurs. At 2610, it is determined (using data collected from the monitoring) whether a predetermined optimum drive condition exists. If the drive condition is determined to be optimum, the resonator continues to be driven at 2606, where driving includes driving with a predetermined waveform.

[0163] If the drive condition is determined not to be optimum at 2610, the drive parameters are updated at 2612. The resonator then continues to be driven, with the updated drive parameters, at 2606.

[0164] Each of the aspects of the embodiments described herein may be employed alone or in combination with one or more of such aspects and/or embodiments. For the sake of brevity, those permutations and combinations will not be discussed separately herein. As such, the described embodiments are not intended to be limiting or exclusive.

[0165] The term "circuit", as used herein may mean, among other things, a single component or a multiplicity of components (whether in integrated circuit form or otherwise), which are active and/or passive, and which are coupled together to provide or perform a desired function. The term "circuitry" may mean, among other things, a circuit (whether integrated or otherwise), a group of such circuits, one or more processors, one or more state machines, one or more processors implementing software, or a combination of one or more circuits (whether integrated or otherwise), one or more state machines, one or more processors, and/or one or

more processors implementing software. The term "data" may mean, among other things, a current or voltage signal(s) whether in an analog or a digital form.

[0166] Aspects of the methods and systems described herein may be implemented in a variety of component types, e.g., metal-oxide semiconductor field- effect transistor ("MOSFET") technologies like complementary metal-oxide semiconductor ("CMOS"), bipolar technologies like emitter-coupled logic ("ECL"), polymer technologies (e.g., silicon-conjugated polymer and metal-conjugated polymer-metal structures), mixed analog and digital, etc.

[0167] The various components and/or functions disclosed herein may be described using any number of combinations of hardware, firmware, and/or as data and/or instructions embodied in various machine-readable or computer-readable media, in terms of their behavioral, register transfer, logic component, and/or other characteristics.

[0168] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of "including, but not limited to." Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words "herein," "hereunder," "above," "below," and words of similar import refer to this application as a whole and not to any particular portions of this application. When the word "or" is used in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list; all of the items in the list; and any combination of the items in the list.

[0169] The above description of illustrated embodiments is not intended to be exhaustive or limited by the disclosure. While specific embodiments of, and examples for, the systems and methods are described herein for illustrative purposes, various equivalent modifications are possible, as those skilled in the relevant art will recognize. For example, the gain control function could be provided in a manner other than clipping. The resonator used in the embodiments may be any kind of resonator, although a microelectromechanical resonator is referred to herein.

Although some embodiments are described with differential coupling, other embodiments may have a mix of differential coupling and single-ended coupling, for example between different amplifier stages. While certain values (e.g., for voltages) are stated in the disclosure, those particular values are illustrative examples only and are not intended to be limiting.

[0170] The teachings provided herein may be applied to other systems and methods, and not only for the systems and methods described above. The elements and acts of the various embodiments described above may be combined to provide further embodiments. These and other changes may be made to methods and systems in light of the above detailed description.

[0171] In general, in the following claims, the terms used should not be construed to be limited to the specific embodiments disclosed in the specification and the claims, but should be construed to include all systems and methods that operate under the claims. Accordingly, the method and systems are not limited by the disclosure, but instead the scope is to be determined entirely by the claims. While certain aspects are presented below in certain claim forms, the inventors contemplate the various aspects in any number of claim forms. Accordingly, the inventors reserve the right to add additional claims after filing the application to pursue such additional claim forms for other aspects as well.