A silicon mems resonator and a method of self-compensating frequency drift by bulk piezoresistive heating of the body thereof

Abstract

The application discloses a silicon MEMS resonator and a body piezoresistive thermal frequency drift self-compensation method thereof. The MEMS oscillator excitation electrode gives an alternating current excitation signal to the resonator, the frequency of which is equal to the frequency of the resonator itself, so that the resonator oscillates. The detection electrode divides the collected resonator oscillation signal into two paths. One path passes through a closed loop oscillation system to realize closed loop oscillation. The other path is sent to a frequency reading device. The frequency reading device collects the signal frequency and transmits the frequency data to a frequency-voltage processing module in real time. The frequency-voltage processing module processes the signal frequency, converts the error between the actual frequency and the set frequency into a voltage signal, realizes digital-analog conversion of the voltage signal through a digital-analog voltage conversion module, inputs the piezoelectric signal to the electrodes at both ends of the MEMS resonant structure, changes the bias voltage, changes the piezoresistive heat generated by the MEMS resonator, and stabilizes the oscillation frequency near the set frequency, thereby realizing compensation of the frequency drift.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of micro-electro-mechanical system, and particularly relates to a silicon MEMS resonator and a method and system for realizing frequency drift self-compensation of bulk piezoresistive heat. BACKGROUND

[0002] In recent years, MEMS resonators have the advantages of miniaturization, high integration with COMS electronics, small inertial acceleration frequency drift, low impurity packaging, strong impact resistance and the like, and thus have the ability to replace traditional quartz crystal oscillators, and have been widely applied in timing and frequency control. How to improve the frequency stability of MEMS resonators and reduce phase noise is a concern of scholars.

[0003] The factors causing the frequency drift of the resonator include changes in environmental temperature, vibration, changes in inertial force, aging and the like. The combination of these factors causes the stability of the resonator to decrease with the increase of oscillation time, and the long-time oscillation stability is several orders of magnitude lower than the short-time oscillation stability. The frequency of the silicon MEMS resonator is most seriously affected by temperature. The stability of the output frequency of the resonator is greatly affected, and in addition, the frequency of the resonator will change with the aging of the material as the use time increases, so the passive and active compensation methods are usually used to reduce the temperature sensitivity and aging rate.

[0004] For the temperature compensation method used in the past active compensation method, the device is complex, and not only a temperature sensor needs to be arranged, but also an environmental heat source needs to be designed. Since the MEMS resonator is in a micro scale, the layout of the heat source and the temperature sensor and the spatial distance from the MEMS resonator will affect the temperature control accuracy. This method has problems such as uncertain temperature field distribution and heat conduction delay, and in addition, the power consumption is large.

[0005] For the voltage-controlled compensation method used in the past active compensation method, the compensation is generated by adjusting the frequency of the resonator itself through the bias voltage, and the actual temperature of the oscillator is the same as the environmental temperature, so it is impossible to maintain the stability of the working environmental temperature of the resonator. The residual stress generated due to the process during the processing cannot be compensated, which will affect the working state of the sensor with the change of temperature.

[0006] In summary, there is an urgent need for a new active compensation method to solve the problems existing in the prior art. SUMMARY

[0007] The technical problem to be solved by the application is to provide a silicon MEMS resonator and a method for realizing frequency drift self-compensation of bulk piezoresistive heat, which changes the conduction current of the silicon resonator to adjust the piezoresistive heat generated by the silicon resonator, and uses the frequency-temperature characteristics of the silicon resonator to compensate for the drift of the resonator frequency caused by external factors.

[0008] The application adopts the following technical solutions:

[0009] A method for realizing self-compensation of frequency drift of a silicon MEMS resonator body piezoresistive thermal frequency, the vibration frequency of the self-excitation oscillation of the silicon MEMS resonator is collected; according to the vibration frequency value, the voltage required for compensating the frequency is calculated by using the temperature-frequency relationship combined with the algorithm; the voltage required for compensating the frequency is converted into a direct current voltage after digital / analog voltage conversion and then output; the direct current voltage is used as the body bias voltage of the silicon MEMS resonator, so that the piezoresistive thermal frequency of the silicon MEMS resonator changes; according to the frequency-temperature characteristics of the silicon resonator, the intrinsic frequency of the silicon MEMS resonator is changed, and the frequency drift of the silicon MEMS resonator caused by the external influence is compensated.

[0010] Specifically, the silicon MEMS oscillator gives the MEMS resonator an alternating current excitation signal through the excitation electrode, and the detection end of the MEMS resonator is connected to the excitation end through the closed loop self-excitation loop of the piezoresistive thermal frequency compensation system to realize self-excitation oscillation.

[0011] Further, the closed loop self-excitation loop is specifically:

[0012] The excitation end excites the intrinsic frequency of the MEMS resonator, and the frequency signal is output to the closed loop circuit with a gain of 1 through the detection end, and the signal is transmitted to the excitation end after being processed by the closed loop circuit.

[0013] Specifically, the MEMS oscillator gives the MEMS resonator an alternating current excitation signal through the excitation electrode, and the detection end of the MEMS resonator is connected to the body heating end through the frequency-temperature compensation loop of the piezoresistive thermal frequency compensation system.

[0014] Further, the body heating end is distributed on both sides of the MEMS resonator.

[0015] Further, the frequency-temperature compensation loop is specifically:

[0016] The bias voltage is set to the body heating end to make the MEMS resonator generate piezoresistive thermal frequency, and the MEMS resonator vibration signal is transmitted to the frequency reading module through the detection end, the frequency reading module transmits the frequency signal to the frequency-voltage processing module in real time, and the frequency-voltage processing module transmits the voltage signal to the body heating end through the digital / analog voltage conversion module to regulate and control the piezoresistive thermal frequency of the MEMS oscillator.

[0017] Further, the frequency reading device is responsible for processing the resonator alternating current oscillation signal fed back by the detection end of the MEMS oscillator, and transmitting the frequency of the detection signal to the frequency-voltage processing module in real time.

[0018] Further, the frequency-voltage processing module is responsible for processing the oscillator frequency transmitted by the frequency reading device, converting the deviation between the corresponding frequency and the initial set frequency into the voltage change, and obtaining the voltage output at this moment, and converting the voltage output into an analog signal input to the digital-analog voltage conversion module, and maintaining the corresponding output state unchanged before the next voltage output change.

[0019] Further, the digital-analog voltage conversion module converts the voltage analog signal transmitted by the frequency-voltage processing module into a digital voltage signal, changes the bias voltage set on the body heating end, so that the piezoresistive heat of the MEMS resonator changes, and the frequency drift of the MEMS resonator caused by the external influence is compensated.

[0020] In the second aspect, a silicon MEMS resonator is used to realize the frequency drift self-compensation method of the silicon MEMS resonator body piezoresistive heat.

[0021] Compared with the prior art, the present application has at least the following beneficial effects:

[0022] The silicon MEMS resonator body piezoresistive heat realizes the frequency drift self-compensation method, when the frequency of the MEMS resonator changes, the frequency offset is converted into the change of the heating voltage at both ends, so that the piezoresistive heat generated by the MEMS resonator changes, the piezoresistive heat of the silicon resonator is regulated, the resonator intrinsic frequency is changed by temperature according to the frequency-temperature characteristics of the silicon resonator, the frequency drift of the silicon MEMS resonator caused by the external influence is compensated, so that the frequency is stable, on the one hand, the control delay caused by the heat conduction time from the heat source to the resonator is avoided, on the other hand, the power loss is reduced, the piezoresistive heat generated is directly used by the resonator, and the power loss in the heat conduction process is maximally reduced.

[0023] Further, the silicon MEMS oscillator gives the MEMS resonator an alternating current excitation signal through the excitation electrode, and the detection end of the MEMS resonator is connected to the excitation end through the closed loop self-excitation circuit of the piezoresistive heat frequency compensation system to realize self-excitation oscillation.

[0024] Further, the closed loop self-excitation circuit specifically is that the excitation end excites the intrinsic frequency of the MEMS resonator, the frequency signal is output to the closed loop circuit with a gain of 1 through the detection end, and the signal is transmitted to the excitation end after being processed by the closed loop circuit.

[0025] Further, the MEMS oscillator gives the MEMS resonator an alternating current excitation signal through the excitation electrode, and the detection end of the MEMS resonator is connected to the body heating end through the frequency-temperature compensation circuit of the piezoresistive heat frequency compensation system.

[0026] Further, the body heating end is distributed on both sides of the MEMS resonator, and the resonator body conducts current to generate piezoresistive heat after a bias voltage is applied to the body heating end.

[0027] Further, the frequency-temperature compensation loop is specifically: a bias voltage is set to the body heating end to make the MEMS resonator generate piezoresistive heat, the MEMS resonator vibration signal is transmitted to the frequency reading module through the detection end, the frequency reading module transmits the frequency signal to the frequency-voltage processing module in real time, the frequency-voltage processing module delivers the voltage signal to the body heating end through the digital / analog voltage conversion module to regulate the piezoresistive heat of the MEMS oscillator.

[0028] Further, the frequency reading device is responsible for processing the resonator alternating current oscillation signal fed back by the detection end of the MEMS oscillator, and transmitting the frequency of the detection signal to the frequency-voltage processing module in real time.

[0029] Further, the frequency-voltage processing module is responsible for processing the oscillator frequency transmitted by the frequency reading device, converting the deviation between the corresponding frequency and the initial set frequency into a voltage change amount, and obtaining the voltage output amount at this moment, converting the voltage output amount into an analog signal and inputting it into the digital / analog voltage conversion module, and maintaining the corresponding output state unchanged before the next voltage output amount changes.

[0030] Further, the digital / analog voltage conversion module converts the voltage analog signal delivered by the frequency-voltage processing module into a digital voltage signal, changes the bias voltage set on the body heating end, so that the piezoresistive heat of the MEMS resonator changes, and the frequency drift of the MEMS resonator caused by the external influence is compensated.

[0031] In summary, the present application utilizes the temperature-frequency characteristics of the silicon resonator, and compensates for the frequency deviation generated by changing the working temperature of the resonator. At this time, the high frequency deviation caused by the change of temperature makes the regulation system maintained at low power consumption have a larger frequency compensation range. In the resonator heating mode, the resonator conduction current is used to generate piezoresistive heat by using its own resistance. This method avoids the control delay caused by the heat conduction time from the heat source to the resonator, and reduces the power loss. The piezoresistive heat generated by the resonator is directly used, which maximally reduces the power loss in the heat conduction process.

[0032] The technical solutions of the present application will be further described in detail below through the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The flowchart of the method of the present application;

[0034] Figure 2The schematic diagram of the device for utilizing the oscillator body piezoresistance heat to compensate the frequency drift in real time according to the application;

[0035] Figure 3 The system diagram of one embodiment of the application;

[0036] Figure 4 The measured temperature-frequency curve and heating power-frequency curve diagram of the resonator according to the application;

[0037] Figure 5 The Allan variance curve diagram of the resonator in the embodiment of the application under the system without compensation and with piezoresistance heat frequency self-compensation.

[0038] 2-1. MEMS resonator; 2-2. Detection end; 2-3. Closed loop circuit; 2-4. Excitation end; 2-5. Frequency reading device; 2-6. Frequency-voltage processing module; 2-7. Digital / analog voltage conversion module; 2-8. Body heating end; 3-1. Amplifier; 3-2. Band pass filter; 3-3. Phase shifter; 3-4. Comparator; 3-5. FPGA; 3-6. Frequency reading module program; 3-7. STM32 frequency-voltage processing module; 3-8. PID control algorithm program; 3-9. ADC digital-analog converter; 4-1. First fixed support anchor point; 4-2. Excitation end fixed support anchor point; 4-3. Excitation end metal electrode; 4-4. Second fixed support anchor point; 4-5. First heating end electrode; 4-6. MEMS disc resonator structure; 4-7. Third fixed support anchor point; 4-8. Detection end electrode; 4-9. Detection end fixed support anchor point; 4-10. Second heating electrode; 4-11. Fourth fixed support anchor point. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0040] In the description of the application, it should be understood that the terms “include” and “contain” indicate the existence of described features, whole, steps, operations, elements and / or components, but do not exclude the existence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0041] It should also be understood that the terms used in the specification and the following claims are for the purpose of describing particular embodiments and are not intended to be limiting, as the specific scope of the invention is disclosed in the attached claims. As used in this specification and the appended claims, the singular forms "a," "an" and "the" encompass both singular and plural referents, unless the context clearly dictates otherwise.

[0042] It should also be further understood that the term "and / or" as used in the specification and in the claims, means any one of the items, or combinations of items, listed are possible and includes all possible combinations, for example A and / or B can mean A alone, B alone, or A and B together. In addition, the character " / " as used herein, generally represents an "or" relationship between the objects before and after it.

[0043] It should be understood that, although the terms first, second, third, etc. can be used herein to describe various ranges or elements, these ranges or elements should not be limited by these terms. These terms are only used to distinguish one range or element from another. For example, a first range could be termed a second range without departing from the scope of the embodiments.

[0044] The word "if" as used herein means "when" or "upon" or "in response to a determination" or "in response to a detection," depending on the context. Similarly, the phrase "if it is determined" or "if [a stated condition or event] is detected" can mean "when it is determined" or "in response to a determination" or "when [a stated condition or event] is detected" or "in response to a detection [of a stated condition or event]," depending on the context.

[0045] Various structural diagrams according to the disclosed embodiments of the present application are shown in the accompanying drawings. These diagrams are not drawn to scale, in which certain details are shown in a somewhat exaggerated manner for purposes of clarity and understanding, and certain other details are omitted. The shapes and relative sizes of the various regions, layers, and the relative positions of the regions / layers shown in the drawings are merely exemplary and can deviate in actual implementation due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, and relative positions can be designed by those skilled in the art according to actual needs.

[0046] The application provides a method for realizing self-compensation of frequency drift of a silicon MEMS resonator body piezoresistive thermal method, an MEMS oscillator excitation electrode is used to give an alternating current excitation signal to the resonator, the frequency of the excitation signal is equal to the frequency of the resonator, so that the resonator oscillates, a detection electrode divides the collected oscillation signal of the resonator into two paths, one path passes through a closed loop oscillation system to realize closed loop oscillation, and the other path is sent to a frequency reading device, the frequency reading device collects the signal frequency, and transmits the frequency data to a frequency-voltage processing module in real time, the frequency-voltage processing module processes the signal frequency, converts the error between the actual frequency and the set frequency into a voltage signal, realizes digital-analog conversion of the voltage signal through a digital-analog voltage conversion module, inputs the piezoelectric signal into electrodes at two ends of the MEMS resonant structure, changes the bias voltage, changes the piezoresistive heat generated by the MEMS resonator, and due to the characteristic that the frequency of the resonator changes with temperature, the oscillation frequency of the resonator is always stable near the set frequency, so that the compensation of the frequency drift is realized.

[0047] The frequency of the silicon resonator changes greatly with temperature, so that the regulation system maintained at low power consumption can have a larger frequency compensation range.

[0048] Please refer to Figure 1 The application discloses a method for realizing self-compensation of frequency drift of a silicon MEMS resonator body piezoresistive thermal method, when the frequency of the MEMS resonator changes, a piezoresistive thermal frequency compensation system converts the frequency offset into the change of the heating voltage at two ends of the resonator, so that the piezoresistive heat generated by the MEMS resonator changes, the intrinsic frequency of the resonator changes due to temperature, and frequency stability is realized.

[0049] S1, the silicon MEMS resonator is self-excited to oscillate;

[0050] S2, a frequency reading device is used to collect the vibration frequency of the self-excited oscillation of the silicon MEMS resonator in step S1, and the vibration frequency value is transmitted to a frequency-voltage processing module in real time in the form of binary;

[0051] S3, the frequency-voltage processing module calculates the voltage required for compensation frequency according to the binary vibration frequency value sent in step S2 by using a temperature-frequency relationship combined algorithm, and transmits the voltage required for compensation frequency to a digital-analog voltage conversion module;

[0052] S4, the digital-analog voltage conversion module converts the voltage required for compensation frequency sent in step S3 and outputs a direct current voltage,

[0053] S5, the direct current voltage output by step S4 is used as the silicon MEMS resonator body bias voltage, so that the piezoresistive heat of the silicon MEMS resonator changes;

[0054] S6, according to the frequency-temperature characteristics of the silicon resonator, the intrinsic frequency of the silicon MEMS resonator is changed by the temperature change of the piezoresistive heat in step S5, the frequency drift of the silicon MEMS resonator caused by the external influence is compensated, and the frequency stability is realized;

[0055] S7, after step S6 is completed, return to step S2, continue to collect the MEMS resonator vibration frequency through the frequency reading device, and perform the next compensation, and the cycle is repeated.

[0056] Please refer to Figure 2 , the silicon MEMS resonator 2-1 has three types of external connection ports, including a detection end 2-2, and an excitation end 2-4 and a body heating end 2-8, wherein the detection end 2-2 is an output port, and the excitation end 2-4 and the body heating end 2-8 are output ports.

[0057] The piezoresistive heat frequency compensation system includes a frequency reading device 2-5, a frequency-voltage processing module 2-6, and a digital / analog voltage conversion module 2-7, which is used to convert the deviation of the frequency signal into the change of the direct current voltage signal; the processing algorithm of the frequency-voltage processing module determines the delay of the compensation time, the ability of regulation and control, the frequency stability deviation and the overshoot; the digital / analog voltage conversion module determines the theoretical minimum accuracy of frequency regulation.

[0058] The frequency reading device 2-5 is responsible for processing the resonator alternating current oscillation signal fed back by the MEMS oscillator detection end 2-2, detecting the frequency of the signal, and converting it into a binary quantity, and transmitting it to the frequency-voltage processing module 2-6 in real time. The accuracy of the frequency reading device 2-5 determines the minimum deviation of the frequency signal processed by the frequency-voltage processing module 2-6, and the detection frequency determines the frequency compensation frequency.

[0059] The frequency-voltage processing module 2-6 is responsible for processing the oscillator frequency transmitted by the frequency reading device, converting the deviation between the frequency and the initial set frequency into a voltage change through an internal algorithm, calculating the voltage output at this moment, converting the voltage into an analog signal, and inputting it to the digital / analog voltage conversion module 2-7, and maintaining the output state unchanged before the next voltage output changes. The processing algorithm of the frequency-voltage processing module 2-6 determines the response delay of the frequency compensation, the ability of regulation and control, the frequency stability deviation and the overshoot.

[0060] The digital-analog voltage conversion module 2-7 converts the voltage analog signal delivered by the frequency-voltage processing module into a digital voltage signal after receiving it, and delivers it to the body heating end 2-8 across the MEMS oscillator, directly regulating the piezoresistive heat of the MEMS oscillator.

[0061] The piezoresistive heat frequency compensation system comprises two loops, including a closed-loop self-excitation loop and a frequency-temperature compensation loop,

[0062] The closed-loop self-excitation loop is specifically:

[0063] The excitation end 2-4 excites the intrinsic frequency of the MEMS resonator 2-1, and outputs the frequency signal to the closed-loop circuit 2-3 with a gain of 1 through the detection end 2-2, and delivers the signal to the excitation end 2-4 after processing by the closed-loop circuit, to realize self-excitation oscillation.

[0064] The frequency-temperature compensation loop is specifically:

[0065] The bias voltage is set on the body heating end 2-8 distributed on both sides of the MEMS resonator 2-1 to make the MEMS resonator generate piezoresistive heat, and the MEMS resonator 2-1 vibration signal is transmitted to the frequency reading module 2-5 through the detection end 2-2, the frequency reading module 2-5 transmits the frequency signal in real time to the frequency-voltage processing module 2-6, the frequency-voltage processing module 2-6 converts the frequency error into a voltage change, and transmits the calculated voltage signal to the digital-analog voltage conversion module 2-7, the digital-analog voltage conversion module 2-7 converts the digital signal into an analog signal, changes the bias voltage set on the body heating end 2-8, so that the piezoresistive heat of the MEMS resonator changes, and due to the frequency-temperature characteristics of the silicon resonator, the resonator intrinsic frequency changes due to temperature, and the cycle is repeated, so as to compensate for the frequency drift of the silicon MEMS resonator caused by external influences.

[0066] The way temperature changes the frequency of the resonator is that the change of temperature causes the change of Young's modulus of silicon material, which in turn affects the frequency,

[0067] The frequency f0 of the silicon MEMS resonator is represented as:

[0068]

[0069] Where k=C k E T ;

[0070] The frequency f of the disk device is represented as:

[0071]

[0072] Where the Young's modulus E T The relationship with temperature is represented as:

[0073] E T = (1 - k E (T - T0)) E0

[0074] wherein E T is the Young's modulus at the operating temperature, E0 is the Young's modulus of the silicon material at a temperature of 297 K, L is the length of the bending beam, k E is the temperature coefficient of the material, T is the operating temperature, T0 is the room temperature, s is the Poisson's ratio, p is the density of the material, r is the radius of the circle, l i is the frequency parameter of the specific mode, and r is the radius of the circle.

[0075] The excitation electrode of the silicon MEMS oscillator gives an alternating excitation signal to the resonator, and the frequency of the signal is equal to the frequency of the resonator itself, so that the resonator oscillates. The detection electrode divides the oscillation signal of the resonator into two paths, one of which passes through the closed loop oscillation system to realize self-excitation oscillation, and the other of which is transmitted to the frequency reading device.

[0076] The silicon MEMS oscillator is composed of a MEMS resonant structure, an excitation electrode, a detection electrode, and a closed loop feedback circuit. The silicon MEMS resonator is provided with electrodes at both ends to conduct heating current, so that it generates piezoresistive heat.

[0077] After the frequency reading device 2-5 processes the signal, the frequency of the signal is transmitted to the frequency-voltage processing module in real time. The frequency-voltage processing module processes the signal frequency, converts the error between the actual frequency and the set frequency into a voltage signal, and realizes digital-to-analog conversion of the voltage signal through the AD conversion module. The piezoelectric signal is input to the electrodes at both ends of the MEMS resonant structure, the bias voltage changes, the piezoresistive heat generated by the MEMS resonator changes, and due to the characteristic that the frequency changes with temperature, the oscillation frequency is always stable near the set frequency, so that the compensation of frequency drift is realized.

[0078] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0079] Please refer to Figure 3In the MEMS resonator, the first fixed anchor 4-1, the second fixed anchor 4-4, the third fixed anchor 4-7 and the fourth fixed anchor 4-11 are connected with the MEMS disk resonant structure 4-6 through respective connecting beams, and are used to support the whole resonant structure.

[0080] The first heating electrode 4-5 is sputtered on the second fixed anchor 4-4, and the second heating electrode 4-10 is sputtered on the fourth fixed anchor 4-11. The heating electrodes are used to set a bias voltage, so that the MEMS disk resonant structure generates a piezoresistive heat.

[0081] The excitation end fixed anchor 4-2 is arranged around the MEMS disk resonant structure 4-6, and is used to fix a capacitive structure formed by the excitation end structure and the MEMS disk resonant structure 4-6. The gap size is 1-10 μm. The excitation end metal electrode layer 4-3 is detected and sputtered on the excitation end fixed anchor 4-2, and is used to apply an external alternating excitation current.

[0082] The detection end fixed anchor 4-9 is arranged around the MEMS disk resonant structure 4-6, and is used to fix a capacitive structure formed by the detection end structure and the MEMS disk resonant structure 4-6. The gap size is 1-10 μm. The excitation end metal electrode layer 4-8 is detected and sputtered on the excitation end fixed anchor 4-9, and is used to output an induced oscillation signal.

[0083] The shapes of the fixed anchors, the excitation anchors and the detection anchors are all square, and the sizes are 100-300 μm. The shapes of the metal electrode layers are all square, and the sizes are 100-300 μm.

[0084] The closed-loop circuit 2-3 includes an amplifier 3-1, a band-pass filter 3-2, a phase shifter 3-3 and a comparator 3-4.

[0085] The frequency reading device 2-5 includes an amplifier 3-1, a band-pass filter 3-2, a phase shifter 3-3, a comparator 3-4, an FPGA 3-5 and a frequency reading module program 3-6 arranged inside the FPGA 3-5.

[0086] The frequency-voltage processing device 2-6 includes an STM32 frequency-voltage processing module 3-7 and a frequency-voltage conversion algorithm and a PID control algorithm 3-8 arranged inside the STM32 frequency-voltage processing module 3-7.

[0087] The digital / analog voltage conversion module is composed of an ADC digital-analog converter 3-9.

[0088] The working principle of the closed-loop self-excitation circuit of the silicon MEMS resonator is as follows:

[0089] The intrinsic frequency of the MEMS disk resonant structure 4-6 is excited by applying an alternating current signal to the excitation end metal electrode layer 4-3, and the frequency signal is output to the closed loop circuit composed of the amplifier 3-1, the band pass filter 3-2, the phase shifter 3-3 and the comparator 3-4 with a gain of 1 through the detection end metal electrode layer 4-8, and after being processed by the closed loop circuit, the signal is transmitted to the excitation end metal electrode layer 4-3 to realize self-excited oscillation.

[0090] The working principle of the frequency-temperature compensation loop is as follows:

[0091] The bias voltage applied to the first heating end electrode 4-5 and the second heating end electrode 4-10 causes the MEMS disk resonant structure 4-6 to generate a piezoresistive heat, and the vibration signal of the MEMS disk resonant structure 4-6 is transmitted to the frequency detection device composed of the amplifier 3-1, the band pass filter 3-2, the phase shifter 3-3, the comparator 3-4, the FPGA 3-5 and the frequency reading module program 3-6 set inside the FPGA 3-5 through the detection end metal electrode layer 4-8, the frequency detection device transmits the frequency signal in real time to the frequency-voltage processing device composed of the STM32 frequency-voltage processing module 3-7 and the frequency-voltage conversion algorithm and PID control algorithm 3-8 set inside the STM32 frequency-voltage processing module 3-7, the frequency-voltage processing device converts the frequency error into a voltage change, transmits the calculated voltage signal to the ADC digital-analog converter 3-9, the ADC digital-analog converter 3-9 converts the digital electrical signal into an analog electrical signal, changes the bias voltage set on the first heating end electrode 4-5 and the second heating end electrode 4-10, so that the piezoresistive heat of the MEMS resonator changes, and due to the frequency-temperature characteristics of the silicon resonator, the resonator intrinsic frequency changes with temperature, and this cycle is repeated, so as to compensate the frequency drift of the silicon MEMS resonator caused by the influence of the external environment.

[0092] Please refer to Figure 4 The measured curve of the resonator temperature-frequency offset and the heating power-frequency offset of the embodiment of the present application, through curve calculation, the frequency change coefficient with temperature is about -2322m / ℃. Through curve calculation, the frequency change coefficient with heating power is about -8.0722m / mW. Therefore, the relationship between the resonator temperature rise and the heating power is about 0.351℃ / mW.

[0093] Please refer to Figure 5 The allan variance curve of the resonator in the non-compensation and piezoresistive heat frequency self-compensation system of the embodiment of the present application, the long-time stability of the resonator through the piezoresistive heat frequency self-compensation system is improved, and the allan variance at 6000s is improved by 2.782x10 3 from 50.5322m to 1.81622b.

[0094] In summary, the silicon MEMS resonator and the body piezoresistive thermal frequency drift self-compensation method and system of the application utilize the temperature-frequency characteristics of the silicon resonator, and compensate the frequency drift generated by changing the working temperature of the resonator. The frequency drift with high temperature variation makes the regulation system with low power consumption have a larger frequency compensation range. In the resonator heating mode, the piezoresistive heat is generated by the conduction current of the resonator and the resistance of the resonator. This method avoids the control delay caused by the heat conduction time from the heat source to the resonator, and reduces the power loss. The piezoresistive heat generated is directly used by the resonator, and the power loss in the heat conduction process is minimized.

[0095] The above is only to illustrate the technical idea of the application, and cannot limit the protection scope of the application. Any modification made according to the technical idea of the application on the basis of the technical scheme falls within the protection scope of the claims of the application.

Claims

1. A method for self-compensation of frequency drift by silicon MEMS resonator body piezoresistive thermal implementation, characterized in that, Collect the vibration frequency of the self-excited oscillation of the silicon MEMS resonator; according to the vibration frequency value, calculate the voltage required for frequency compensation by using the temperature-frequency relationship combined algorithm; output a direct current voltage after analog-digital voltage conversion of the voltage required for frequency compensation; use the direct current voltage as the body bias voltage of the silicon MEMS resonator, so that the piezoresistive heat of the silicon MEMS resonator changes; change the intrinsic frequency of the silicon MEMS resonator according to the silicon resonator frequency-temperature characteristic, and compensate for the frequency drift of the silicon MEMS resonator caused by external influences; The MEMS oscillator gives the MEMS resonator an alternating current excitation signal through the excitation electrode, and the detection end of the MEMS resonator is connected to the body heating end through the frequency-temperature compensation loop of the piezoresistive heat frequency compensation system. The frequency-temperature compensation loop is specifically: The bias voltage is set to the body heating end to make the MEMS resonator generate piezoresistive heat. The MEMS resonator vibration signal is transmitted to the frequency reading module through the detection end. The frequency reading module transmits the frequency signal to the frequency-voltage processing module in real time. The frequency-voltage processing module transmits the voltage signal to the body heating end through the analog-digital voltage conversion module to regulate and control the piezoresistive heat of the MEMS oscillator. The frequency-voltage processing module is responsible for processing the oscillator frequency transmitted by the frequency reading device, converting the deviation between the corresponding frequency and the initial set frequency into a voltage change, and obtaining the voltage output at the corresponding time. The voltage output is converted into an analog signal and input into the analog-digital voltage conversion module. Before the next voltage output changes, the corresponding output state remains unchanged.

2. The method of claim 1, wherein the frequency drift self-compensation is achieved by a thermal process. The silicon MEMS oscillator gives the MEMS resonator an alternating current excitation signal through the excitation electrode, and the detection end of the MEMS resonator is connected to the excitation end through the closed loop self-excitation loop of the piezoresistive heat frequency compensation system to realize self-excitation.

3. The method of claim 2, wherein the frequency drift self-compensation is achieved by a thermal process. The closed loop self-excitation loop is specifically: The excitation end excites the intrinsic frequency of the MEMS resonator, and outputs the frequency signal to the closed loop circuit with a gain of 1 through the detection end. After processing by the closed loop circuit, the signal is transmitted to the excitation end.

4. The method of claim 1, wherein the frequency drift self-compensation is achieved by a thermal process. The body heating end is distributed on both sides of the MEMS resonator.

5. The method of claim 1, wherein the frequency drift self-compensation is achieved by a thermal process. The frequency reading device is responsible for processing the resonator alternating current oscillation signal fed back by the detection end of the MEMS oscillator, and transmits the frequency of the detection signal to the frequency-voltage processing module in real time.

6. The method of claim 1, wherein the frequency drift self-compensation is achieved by a thermal process. The analog-digital voltage conversion module converts the voltage analog signal transmitted by the frequency-voltage processing module into a digital voltage signal, changes the bias voltage set on the body heating end, so that the piezoresistive heat of the MEMS resonator changes, and compensates for the frequency drift of the MEMS resonator caused by external influences.

7. A silicon MEMS resonator, characterized by, Use the silicon MEMS resonator body piezoresistive heat to realize the frequency drift self-compensation method according to any one of claims 1-6.

Images