A system and method for disciplining and holding MEMS oscillators based on a dual-bridge structure.

Abstract

This invention discloses a discipline and hold system and method based on a dual-bridge MEMS oscillator, comprising: a GNSS receiver and a dual-bridge MEMS oscillator. The output terminals of the GNSS receiver and the dual-bridge MEMS oscillator are connected to a high-precision phase measurement module. The output terminal of the high-precision phase measurement module is connected to an MCU. The output terminal of the MCU is connected to a DAC conversion module. The output terminal of the DAC conversion module is connected to the dual-bridge MEMS oscillator. The dual-bridge MEMS oscillator outputs a signal to the high-precision phase measurement module through a phase-locked loop (PLL) frequency divider module. A temperature acquisition module is connected to the MCU, and a power supply module is also included to power the system. The MCU includes an EEPROM chip storing temperature compensation and aging time compensation model fitting data. This effectively improves the frequency accuracy and long-term frequency stability of the MEMS oscillator.

Description

Technical Field

[0001] This invention relates to the field of crystal oscillator technology, and in particular to a discipline and hold system and method for MEMS oscillators based on a dual-bridge structure. Background Technology

[0002] Traditional crystal oscillators suffer from insufficient accuracy, weak vibration resistance, and susceptibility to environmental interference in applications with extremely high frequency requirements. Meanwhile, the miniaturization trend in modern electronic devices is becoming increasingly significant, leading to the development of Microelectromechanical Systems (MEMS) technology and the emergence of MEMS oscillators. Compared to traditional oscillators, MEMS oscillators offer several significant advantages, such as smaller size, allowing integration into small electronic devices and enhancing device integration and portability. Furthermore, MEMS oscillators have low power consumption, effectively reducing overall device energy consumption, and also possess strong shock resistance and impact tolerance. However, their frequency stability is still affected by various factors.

[0003] In complex working environments, factors such as temperature changes, mechanical stress, and power supply voltage fluctuations can all cause frequency drift in MEMS oscillators. This is especially true for dual-bridge MEMS oscillators, whose unique dual-bridge structure, while offering some performance advantages, also makes them more sensitive to environmental factors. For example, even small temperature changes can cause thermal expansion or contraction of the dual-bridge materials, leading to uneven stress distribution within the structure and consequently altering the oscillator's resonant frequency.

[0004] Existing oscillator discipline methods are primarily designed for traditional quartz crystal oscillators and have poor adaptability to MEMS oscillators. While some methods can be used with general MEMS oscillators, they cannot effectively address the frequency drift problem arising from the unique structure of dual-bridge MEMS oscillators. These methods are insufficient in terms of accuracy, complexity, and cost, failing to meet the high-precision frequency output requirements of modern electronic systems based on dual-bridge MEMS oscillators. Therefore, there is an urgent need for a discipline method specifically designed for the unique structure of dual-bridge MEMS oscillators to improve their frequency stability and ensure the reliable operation of electronic systems. Summary of the Invention

[0005] This invention provides a system and method for taming and holding a MEMS oscillator based on a dual-bridge structure. The piezoelectric layer of the dual-bridge MEMS oscillator employs a unique dual-bridge design and uses materials with high stability and low temperature coefficient, resulting in minimal frequency variation of the resonator under different temperature environments and greatly improving the stability of its inherent frequency. Based on this, the taming and holding system is further equipped with an EEPROM chip storing temperature compensation and aging time compensation model fitting data, which effectively improves the frequency accuracy and long-term frequency stability of the MEMS oscillator.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, embodiments of the present invention provide a discipline and hold system based on a dual-bridge MEMS oscillator, comprising: a GNSS receiver and a dual-bridge MEMS oscillator; the output terminals of the GNSS receiver and the dual-bridge MEMS oscillator are connected to a high-precision phase measurement module; the output terminal of the high-precision phase measurement module is connected to an MCU; the output terminal of the MCU is connected to a DAC conversion module; the output terminal of the DAC conversion module is connected to the dual-bridge MEMS oscillator via a signal conditioning circuit; the dual-bridge MEMS oscillator outputs a signal to the high-precision phase measurement module via a phase-locked loop (PLL) frequency divider module; a temperature acquisition module is connected to the MCU; and a power supply module is also included to power the system; wherein the MCU includes an EEPROM chip, and the EEPROM chip stores temperature compensation and aging time compensation model fitting data.

[0008] In some possible embodiments, the temperature compensation model fits the data, and the method for obtaining the data includes:

[0009] A temperature compensation mathematical model is established, and a polynomial compensation algorithm is adopted to fit the adjustment frequency y-temperature x curve using a high-order polynomial, specifically a fourth-order polynomial y = a0 + a1x + a2x. 2 +a3x 3 +a4x, where a0=0.4688, a1=-0.0733, a2=-0.0022, a3=0.00025, a4=-0.0000015. By measuring the frequency of the dual-bridge MEMS oscillator at different temperature points, a large number of experimental data points are obtained to fit a well-fitted fourth-order polynomial. At the same time, the fitted adjustment frequency y-temperature x data is stored in the EEPROM chip of the MCU.

[0010] In some possible embodiments, the aging time compensation model fitting data is obtained by methods including:

[0011] A mathematical model for aging time compensation is established, specifically using f(t) - f0 = alan(t + t0).

[0012] f(t) is the frequency at time t, f0 is the initial frequency, and a is a constant related to the aging rate.

[0013] By measuring the frequency of the dual-bridge MEMS oscillator at different time points, a large number of experimental data points are obtained to fit the aging time compensation mathematical formula. At the same time, the fitted adjustment frequency (f(t)-f0)-time t data is stored in the EEPROM chip of the MCU.

[0014] In some possible embodiments, the dual-bridge MEMS oscillator includes a dual-bridge MEMS resonator with a piezoelectric layer disposed within it. The piezoelectric layer is a symmetrical structure with the center line of a square central anchor as its longitudinal axis of symmetry. A first connecting beam and a first circular ring, as well as a second connecting beam and a second circular ring, are sequentially connected to both sides of the central anchor. The centers of the first connecting beam, the second connecting beam, the first circular ring, and the second circular ring are all on the same straight line, which is also the transverse axis of symmetry of the piezoelectric layer. The longitudinal axis of symmetry and the transverse axis of symmetry are perpendicular to each other. The height of the piezoelectric layer structure is relatively uniform, exhibiting a rectangular shape. The height of the structure is related to the vibration characteristics of the dual-ring structure; the uniform height helps ensure the stability of the structure during vibration.

[0015] In some possible embodiments, the inner and outer radii of the first and second circular rings are determined by a preset frequency threshold f0, which is approximately:

[0016]

[0017] Where R1 and R2 represent the inner and outer radii of the first and second circular rings, respectively, E is the Young's modulus of the material used, and ρ is the density of the material used.

[0018] In some possible embodiments, the lengths of the first and second connecting beams are calculated using a quarter-wavelength coupling method, matching the breathing mode frequencies f0 of the first and second circular rings with the extension mode frequencies of the first and second connecting beams, and then calculating the length L of the first and second connecting beams using a formula:

[0019]

[0020] Where Vl represents the velocity of sound waves in the direction of the piezoelectric layer.

[0021] In some possible embodiments, the piezoelectric layer uses monocrystalline silicon, and the electrode portion uses gold as the electrode material.

[0022] In some possible embodiments, a phase-locked frequency divider module is also included, the input of which is connected to the output of the GNSS receiver, and the output is connected to the high-precision phase measurement module.

[0023] In some possible embodiments, the MCU also includes discipline and hold frequency control software for controlling the discipline and hold of a preset frequency threshold based on a dual-bridge MEMS oscillator.

[0024] Secondly, embodiments of the present invention provide a method for disciplining and maintaining a MEMS oscillator based on a dual-bridge structure, the method comprising the following steps:

[0025] When the system is powered on, a preset frequency threshold is set. Based on the initial frequency value of the dual-bridge MEMS oscillator, the MCU reads the preset initial reference first adjustment frequency and configuration parameters from the EEPROM chip. The configuration parameters include the setting of internal registers, port initialization, clock configuration, etc.

[0026] The MCU reads the preset initial reference first adjustment frequency and inputs it into the DAC conversion module. The DAC adjusts the frequency of the dual-bridge MEMS oscillator to change the initial frequency into the second frequency.

[0027] The second frequency, after being processed by a phase-locked frequency divider, is input to the high-precision phase measurement module; the GNSS receiver receives the standard frequency, which, after being processed by a phase-locked frequency multiplier module, is also input to the high-precision phase measurement module; the high-precision phase measurement module compares the second frequency and the standard frequency to obtain the phase difference data;

[0028] The temperature acquisition module begins collecting ambient temperature data and transmits the ambient temperature data to the MCU;

[0029] The MCU receives phase difference data to calculate adjustment frequency data; simultaneously, the MCU reads the corresponding temperature compensation data from the EEPROM chip based on the ambient temperature data, and reads the corresponding aging compensation data from the EEPROM chip based on the aging time data; the MCU calculates and obtains the second adjustment frequency data, and adjusts the frequency of the dual-bridge MEMS oscillator through the DAC to change the second frequency into the third frequency;

[0030] The process of processing the second frequency is repeated for the third frequency, and this cycle is repeated N times until the Nth frequency is adjusted to meet the preset frequency threshold.

[0031] During system operation, the MCU continuously monitors the data from the high-precision phase measurement module and temperature data, and adjusts the frequency of the MEMS oscillator in real time.

[0032] EEPROM is updated and stored regularly. Temperature and aging data are collected to ensure system stability during long-term operation.

[0033] The advantages of this invention are:

[0034] This invention relates to a discipline and hold system and method for MEMS oscillators based on a dual-bridge structure. The dual-bridge MEMS oscillator employs a unique dual-bridge design for its piezoelectric layer, featuring a symmetrical structure with the centerline of a square central anchor as its longitudinal axis of symmetry. Two independent symmetrical rings are connected to the two sides of the central anchor via two bridges. These two independent rings and the strip structure are excited in an extended vibration mode. This mode exhibits complete symmetry with respect to the central anchor point, effectively suppressing anchor point loss transmitted to the substrate. Furthermore, the extended vibration mode exhibited in the rings and strip structure possesses an extremely low strain gradient. This characteristic significantly reduces energy loss caused by thermoelastic dissipation. Furthermore, the piezoelectric layer uses single-crystal silicon, and the electrodes use gold, which has a low temperature coefficient, resulting in minimal frequency variation of the resonator under different temperature conditions. These factors combined greatly improve the stability of the inherent frequency, providing a stable frequency reference for high-precision crystal oscillators. Based on this, an EEPROM chip storing temperature compensation and aging time compensation model fitting data is further configured in its discipline and hold system, greatly improving the MCU's computing speed. Specifically, a fourth-order polynomial y = a0 + a1x + a2x is used. 2 +a3x 3 The +a4x compensation algorithm is used to fit the frequency-temperature-x curve. By measuring the frequency of the dual-bridge MEMS oscillator at different temperature points, a large number of experimental data points are obtained to fit a well-fitted fourth-order polynomial, which effectively improves the frequency accuracy and long-term frequency stability of the MEMS oscillator. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the discipline and hold system based on a dual-bridge MEMS oscillator according to an embodiment of the present invention;

[0036] Figure 2a 2b and 2c are the front view, top view, and left (right) view of the piezoelectric layer of the discipline and hold system based on a dual-bridge MEMS oscillator according to an embodiment of the present invention.

[0037] Figure 3 This is a flowchart illustrating the discipline and hold method based on a dual-bridge MEMS oscillator according to an embodiment of the present invention.

[0038] Figure 4 This is a circuit diagram of a MEMS oscillator based on a dual-bridge structure, according to an embodiment of the present invention.

[0039] In the diagram, 1-central anchor, 21-first circular ring, 22-second circular ring, 31-first connecting beam, 32-second connecting beam, 4-height of piezoelectric layer structure, 100-temperature control circuit, 200-frequency signal generation circuit (where G1 is a dual-bridge MEMS resonator), 300-starting circuit of frequency signal generation circuit, 400-two-stage discharge circuit of frequency signal generation circuit. Detailed Implementation

[0040] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. At the same time, in the description of the embodiments of this application, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0041] Example 1

[0042] This invention provides a discipline and hold system based on a dual-bridge MEMS oscillator, see [link to relevant documentation]. Figure 1 ,include:

[0043] The system comprises a GNSS receiver and a dual-bridge MEMS oscillator. The outputs of the GNSS receiver and the dual-bridge MEMS oscillator are connected to a high-precision phase measurement module. The output of the high-precision phase measurement module is connected to an MCU. The output of the MCU is connected to a DAC conversion module. The output of the DAC conversion module is connected to the dual-bridge MEMS oscillator via a signal conditioning circuit. The dual-bridge MEMS oscillator outputs a signal to the high-precision phase measurement module via a phase-locked loop (PLL) frequency divider module. The MCU includes a temperature acquisition module and a power supply module to power the system. The MCU includes an EEPROM chip storing temperature compensation and aging time compensation model fitting data. In this embodiment, a PLL frequency divider module is also included. The input of the PLL frequency divider module is connected to the output of the GNSS receiver, and the output is connected to the high-precision phase measurement module. In this embodiment, the MCU also includes discipline and hold frequency control software, which is programmed into the MCU's flash chip and used to control the discipline and hold of the dual-bridge MEMS oscillator based on a preset frequency threshold.

[0044] The dual-bridge MEMS oscillator of this embodiment includes a dual-bridge MEMS resonator and an oscillation circuit. A piezoelectric layer is disposed within the dual-bridge MEMS resonator. The piezoelectric layer has a symmetrical structure with the center line of a square central anchor as its longitudinal axis of symmetry. In this embodiment, the central anchor is rectangular, with its longitudinal axis of symmetry being its center line. A first connecting beam and a first circular ring, as well as a second connecting beam and a second circular ring, are sequentially connected to both sides of the central anchor. The centers of the first connecting beam, the second connecting beam, the first circular ring, and the second circular ring are all on the same straight line, which is also the transverse axis of symmetry of the piezoelectric layer. The longitudinal and transverse axes of symmetry are perpendicular to each other. The first and second circular rings have identical structures. The first and second connecting beams are also identical rectangular strip structures, with their longitudinal axis of symmetry coinciding with the transverse axis of symmetry. The piezoelectric layer structure has a relatively uniform height, exhibiting a rectangular shape. The height of the structure is related to the vibration characteristics of the double-ring structure; the uniform height helps ensure the stability of the structure during vibration. The two independent circular rings and the strip structure are excited in an extended vibration mode, which exhibits complete symmetry with respect to the central anchor (point), effectively suppressing anchor point loss transmitted to the substrate. Furthermore, the extended vibration mode exhibited in the circular rings and strip structure has extremely low strain gradient characteristics. This characteristic significantly reduces energy loss caused by thermoelastic dissipation, playing a crucial role in improving the stability of its natural frequency. In summary, the symmetry of the double-ring structure has a significant impact on its performance. Ensuring the symmetry of the double rings in shape, size, and material can reduce the complexity of vibration modes and frequency splitting caused by asymmetry. Through optimized design, making the double rings as symmetrical as possible can improve frequency uniformity and stability, which is beneficial for the MEMS oscillator to output a pure frequency signal. In this embodiment, the inner and outer radii of the first and second circular rings are determined by a preset frequency threshold f0, which is approximately:

[0045]

[0046] Where R1 and R2 represent the inner and outer radii of the first and second circular rings, respectively, E is the Young's modulus of the material used, and ρ is the density of the material used.

[0047] In this embodiment, the lengths of the first and second connecting beams are determined using a quarter-wavelength coupling method. The breathing mode frequencies f0 of the first and second circular rings are matched with the extension mode frequencies of the first and second connecting beams, and the lengths L of the first and second connecting beams are calculated using a formula.

[0048]

[0049] Among them, V l This indicates the velocity of sound waves in the direction of the piezoelectric layer.

[0050] In this embodiment, the piezoelectric layer uses monocrystalline silicon, and the electrode part uses gold as the electrode material. The material has a low temperature coefficient, which makes the frequency change of the resonator very small under different temperature environments.

[0051] Oscillating circuits, such as Figure 3 As shown, the circuit uses a low-noise amplifier, which can effectively amplify the signal while minimizing the introduction of additional noise, ensuring the purity of the signal, and further improving the output frequency signal quality of the dual-bridge MEMS oscillator. This provides a high-quality input frequency signal for the subsequent frequency comparison and control adjustment of the high-precision phase measurement module.

[0052] The oscillation circuit is divided into a temperature control circuit ( Figure 4 100 in the middle) and frequency signal generation circuit ( Figure 4 The two parts are 200.

[0053] The temperature control circuit uses power transistor V2 to control the circuit temperature. It adjusts the base current to control the collector current, thereby controlling the temperature of the heat sink chip. The base current is determined by the voltage division of the thermistor R10, and the current from the base is amplified through two discharge circuits (amplifiers N2 and N3), thus enhancing the power transistor's sensitivity to the circuit.

[0054] The signal generation circuit consists of an oscillation circuit ( Figure 4 The system consists of three parts: a 300MHz crystal oscillator, an amplifier circuit, and an inverter. The oscillator circuit is a three-point capacitor oscillator circuit, with L4 and C23 connected in series and L6 connected in parallel to suppress resonance of the crystal oscillator at other frequencies. Simultaneously, it uses a two-stage discharge circuit (…). Figure 4 The signal generated by the 400 amplified crystal oscillator is amplified by N5, which is an inverter. The signal is converted into a square wave signal by the inverter.

[0055] In this embodiment, a temperature compensation model is used to fit the data. The method for obtaining the fitted data includes:

[0056] A temperature compensation mathematical model is established, and a polynomial compensation algorithm is adopted to fit the adjustment frequency y-temperature x curve using a high-order polynomial, specifically a fourth-order polynomial y = a0 + a1x + a2x. 2 +a3x 3+a4x, where a0=0.4688, a1=-0.0733, a2=-0.0022, a3=0.00025, a4=-0.0000015, by measuring the frequency of the dual-bridge MEMS oscillator at different temperature points, a large number of experimental data points are obtained to fit a well-fitted fourth-order polynomial with high data accuracy; at the same time, the fitted adjustment frequency y-temperature x data is stored in the EEPROM chip of the MCU, which can be retrieved at any time during MCU calculation. Multiple high-sensitivity temperature sensors are built into the temperature acquisition module and distributed around the MEMS resonator and in key circuit parts. Temperature acquisition uses thermistors with leads, which can be flexibly placed in any position. The MCU receives ambient temperature data, accurately predicts the effect of temperature on frequency, and adjusts the output frequency in time to ensure that the crystal oscillator maintains high accuracy over a wide temperature range, which greatly improves the MCU's control efficiency in disciplining and maintaining frequency stability.

[0057] The methods for obtaining data for fitting the aging time compensation model include:

[0058] A mathematical model for aging time compensation is established, specifically using f(t)-f0=aln(t+t0), where f(t) is the frequency at time t, f0 is the initial frequency, and a is a constant related to the aging rate.

[0059] By measuring the frequency of the dual-bridge MEMS oscillator at different time points, a large number of experimental data points are obtained to fit a well-fitted mathematical formula for aging time compensation. At the same time, the fitted adjustment frequency (f(t)-f0)-time t data is stored in the EEPROM chip of the MCU, which can be retrieved at any time during MCU calculation, greatly improving the MCU's control efficiency in disciplining and maintaining frequency stability.

[0060] According to the technical solution of this embodiment, the inventor specifically designed a dual-bridge MEMS oscillator, wherein the specific parameters of the dual-bridge MEMS resonator and the piezoelectric layer disposed therein are described here. The operating frequency of the dual-bridge MEMS resonator is approximately 10.6MHz. The piezoelectric layer of the resonator consists of two symmetrical rings, which are connected by two identical beams anchored at a central node. The MEMS structure, in the top view, presents two interconnected ring structures (a first circular ring and a second circular ring). Each ring structure is circular, with an inner diameter of 115μm and an outer diameter of 125μm. The two ring structures are connected together by a rectangular connecting beam (a first connecting beam and a second connecting beam), which is approximately 200μm long and 12μm wide. The two ring structures are symmetrically distributed in the longitudinal direction, and the connecting beam is located on the transverse axis, connecting the two rings together. The entire structure is also symmetrical in the transverse direction. The front view Figure 2(a) shows the thickness distribution of the dual-ring structure. The dual-ring structure extends in the transverse direction, with a length of approximately 620μm. Figure 2(c) shows the height distribution of the double-ring structure. The double-ring structure extends along the horizontal axis, with a length of approximately 620 μm and a height of approximately 20 μm. The height of the structure is relatively uniform, exhibiting a rectangular shape. The height of the structure is related to its vibration characteristics; a uniform height helps ensure the stability of the structure during vibration. The size of the rings is a key parameter in the double-ring structure. Optimizing the diameter, width, and other dimensions of the rings can affect the frequency characteristics of the MEMS. The connection structure between the two rings needs optimization. Optimizing the shape, size, and position of the connection structure can improve the coupling strength between the two rings. A reasonable connection structure can ensure efficient and stable energy transfer between the two loops, contributing to improved frequency stability and the overall performance of the oscillator. Symmetry is crucial to the performance of the double-ring structure. Ensuring symmetry in the shape, size, and material of the double rings can reduce the complexity of vibration modes and frequency splitting caused by asymmetry. Optimizing the design to make the double rings as symmetrical as possible can improve the uniformity and stability of the frequency, which is beneficial for the MEMS oscillator to output a clean frequency signal.

[0061] Example 2

[0062] This invention provides a method for disciplining and maintaining a MEMS oscillator based on a dual-bridge structure, comprising the following steps:

[0063] When the system is powered on, the MCU reads the preset initial reference first adjustment frequency and configuration parameters from the EEPROM chip based on the initial frequency value of the dual-bridge MEMS oscillator.

[0064] The MCU reads the preset initial reference first adjustment frequency and inputs it into the DAC conversion module. The DAC adjusts the frequency of the dual-bridge MEMS oscillator to change the initial frequency into the second frequency.

[0065] The second frequency, after being processed by a phase-locked frequency divider, is input to the high-precision phase measurement module; the GNSS receiver receives the standard frequency, which, after being processed by a phase-locked frequency multiplier module, is also input to the high-precision phase measurement module; the high-precision phase measurement module compares the second frequency and the standard frequency to obtain the phase difference data;

[0066] The temperature acquisition module begins collecting ambient temperature data and transmits the ambient temperature data to the MCU;

[0067] The MCU receives phase difference data to calculate adjustment frequency data; simultaneously, the MCU reads the corresponding temperature compensation data from the EEPROM chip based on the ambient temperature data, and reads the corresponding aging compensation data from the EEPROM chip based on the aging time data; the MCU calculates and obtains the second adjustment frequency data, and adjusts the frequency of the dual-bridge MEMS oscillator through the DAC to change the second frequency into the third frequency;

[0068] The process of processing the second frequency is repeated for the third frequency, and this cycle is repeated N times until the Nth frequency is adjusted to meet the preset frequency threshold.

[0069] During system operation, the MCU continuously monitors the data from the high-precision phase measurement module and temperature data, and adjusts the frequency of the MEMS oscillator in real time.

[0070] The EEPROM is periodically updated and stores temperature compensation data and aging data.

Claims

1. A dual-bridge structure based MEMS oscillator taming and holding system, characterized in that, The system comprises a GNSS receiver and a double-bridge structure MEMS oscillator, an output end of the GNSS receiver and the double-bridge structure MEMS oscillator is connected to a high-precision phase measurement module, an output end of the high-precision phase measurement module is connected to an MCU, an output end of the MCU is connected to a DAC conversion module, an output end of the DAC conversion module is connected to the double-bridge structure MEMS oscillator, the double-bridge structure MEMS oscillator outputs a signal to the high-precision phase measurement module through a phase-locked frequency division module, a temperature acquisition module is connected to the MCU, and a power supply module is arranged to supply power to the system; wherein the MCU comprises an EEPROM chip, and temperature compensation and aging time compensation model fitting data are stored in the EEPROM chip; The double-bridge structure MEMS oscillator comprises a double-bridge structure MEMS resonator, and a piezoelectric layer is arranged in the double-bridge structure MEMS resonator; the piezoelectric layer is a symmetrical structure with a center line of a square central anchor as a longitudinal symmetry axis; first connecting beams and first circular rings, and second connecting beams and second circular rings are sequentially connected on both sides of the central anchor; centers of the first connecting beams, the second connecting beams, the first circular rings and the second circular rings are located on the same straight line, the same straight line is also a transverse symmetry axis of the piezoelectric layer, and the longitudinal symmetry axis and the transverse symmetry axis are perpendicular to each other. The temperature compensation model fitting data are obtained by the following method:

2. The dual-bridge structure based MEMS oscillator taming and holding system according to claim 1, wherein, The aging time compensation model fitting data are obtained by the following method: A temperature compensation mathematical model is established, and a polynomial compensation algorithm is used to use a high-order polynomial to fit the frequency-temperature x curve, specifically a fourth-order polynomial y=a0+a1x+a2x 2 +a3x 3 +a4x, wherein a0=0.4688, a1=-0.0733, a2=-0.0022, a3=0.00025, a4=-0.0000015 By measuring the frequency of the double-bridge structure MEMS oscillator at different temperature points, a large number of test data points are obtained to fit the fitted fourth-order polynomial, and the fitted frequency-temperature x data is stored in the EEPROM chip of the MCU.

3. The dual-bridge structure based MEMS oscillator taming and holding system according to claim 1 or 2, wherein, An aging time compensation mathematical model is established, and the model is specifically f(t)-f0=aln(t+t0), wherein f(t) is a frequency at a moment, f0 is an initial frequency, and a is a constant related to an aging rate; A large number of test data points are obtained by measuring frequencies of the double-bridge structure MEMS oscillator at different time points, and a fitting aging time compensation mathematical formula is obtained; meanwhile, adjusted frequency (f(t)-f0)-time t data are stored in an EEPROM chip of the MCU. Inner radii and outer radii of the first circular rings and the second circular rings are determined according to a preset frequency threshold f0, and the preset frequency threshold is approximately 4. The dual-bridge structure based MEMS oscillator taming and holding system according to claim 3, wherein, wherein R1 and R2 represent the inner radii and the outer radii of the first circular rings and the second circular rings, E is a Young's modulus of a material used, and p is a density of the material used. Lengths of the first connecting beams and the second connecting beams are calculated by using a quarter wavelength coupling method to match the breathing mode frequency f0 of the first circular rings and the second circular rings with the extension mode frequency of the first connecting beams and the second connecting beams, and the lengths L of the first connecting beams and the second connecting beams are calculated by using a formula.

5. The dual-bridge structure based MEMS oscillator taming and holding system of claim 4, wherein, The piezoelectric layer uses single crystal silicon, and gold is used as an electrode material for an electrode part. where V l represents the speed of sound in the piezoelectric layer direction.

6. The dual-bridge structure based MEMS oscillator taming and holding system according to any one of claims 4-5, wherein, The system further comprises a phase-locked frequency division module, an input end of the phase-locked frequency division module is connected to an output end of the GNSS receiver, and an output end of the phase-locked frequency division module is connected to the high-precision phase measurement module.

7. The dual-bridge structure based MEMS oscillator taming and holding system of claim 6, wherein, The MCU further comprises a tame and keep frequency control software for controlling the double-bridge structure MEMS oscillator to tame and keep the preset frequency threshold.

8. The dual-bridge structure based MEMS oscillator taming and holding system according to any one of claims 7, wherein, ​ 9. A taming and holding method of a dual-bridge structure MEMS oscillator, characterized by, The dual-bridge structure MEMS oscillator taming and maintaining system based on claim 8, the method comprises the following steps: Power on to start the system, when the system starts, the MCU reads the preset initial reference first adjustment frequency and configuration parameters from the EEPROM chip according to the initial frequency value of the dual-bridge structure MEMS oscillator; The MCU inputs the read preset initial reference first adjustment frequency into the DAC conversion module, and adjusts the frequency of the dual-bridge structure MEMS oscillator through the DAC to change the initial frequency into a second frequency; The second frequency is input into the high-precision phase measurement module after phase-locked frequency division processing; the GNSS receiver receives a standard frequency, which is also input into the high-precision phase measurement module after phase-locked frequency multiplication processing; The high-precision phase measurement module compares the second frequency and the standard frequency to obtain phase difference data; The temperature acquisition module starts to collect environmental temperature data and transmits the environmental temperature data to the MCU; The MCU receives the phase difference data for calculating adjustment frequency data; at the same time, the MCU reads corresponding temperature compensation data from the EEPROM chip according to the environmental temperature data and reads corresponding aging compensation data from the EEPROM chip according to the aging time data; the MCU obtains second adjustment frequency data through calculation, and adjusts the frequency of the dual-bridge structure MEMS oscillator through the DAC to change the second frequency into a third frequency; The process of the second frequency is repeated for the third frequency, and the cycle is repeated N times until the Nth frequency is adjusted to meet the preset frequency threshold; During the system operation, the MCU constantly monitors the data of the high-precision phase measurement module and the temperature data, and adjusts the frequency of the MEMS oscillator in real time; The EEPROM regularly updates and stores the temperature compensation data and the aging data.

Images