Weak coupling double-end tuning fork MEMS electric field sensor

Abstract

The invention discloses a weak coupling double-end tuning fork MEMS electric field sensor, and belongs to the technical field of MEMS sensors, and the weak coupling double-end tuning fork MEMS electric field sensor is provided with a first resonator, a second resonator, a weak coupling mechanical beam, a first mass block, a second mass block, a driving electrode, a DC bias electrode, a disturbance electrode, an adjusting electrode, a first induction electrode, and a second induction electrode. The first resonator and the second resonator are arranged in parallel in a staggered manner on the same horizontal plane along the horizontal direction and are connected through the weak coupling mechanical beam; the driving electrode and the first induction electrode are respectively arranged on two sides of the first resonator, and the disturbance electrode and the second induction electrode are respectively arranged on two sides of the second resonator; the direct-current bias electrode and the adjusting electrode are arranged on the two sides of the second resonator respectively; the two sides of the first resonator are respectively provided with a first mass block, and the two sides of the second resonator are respectively provided with a second mass block. The method has the advantages of high performance, simplicity in manufacturing, low cost and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS sensors, and in particular to a weakly coupled double-ended tuning fork micro-electro-mechanical systems (MEMS) electric field sensor. Background Art

[0002] As a core instrument that can detect electric fields, micromechanical electric field sensors have been widely used in meteorology, petrochemicals, aerospace, power grids, and biomedicine. Compared with traditional non-MEMS field-milling electric field sensors, micrometer-scale MEMS electric field sensors have many advantages such as small size and low power consumption, which has promoted the development of micromechanical sensors. At present, the more mature MEMS electric field sensors mainly include micro-field milling and electric field sensors based on electro-optical effect, which have many advantages such as low cost and simple principle. Micro-field milling electric field sensors generally use sensing electrodes to sense external electric fields, causing changes in the capacitance gap between the shielding electrode to detect external electric fields. With its performance advantages, it has been put into use in the meteorological field, with a resolution of 40V / m, which can meet the detection needs of thunderstorm weather. However, the electric field detection changes on sunny days can generally reach several V / m. The power grid and biomedical fields have higher performance requirements for electric field sensors, and the current MEMS electric field sensors still cannot meet the needs of these fields.

[0003] In recent years, in response to the demand for high-performance sensors, a modal localization phenomenon based on a weakly coupled resonant system has been successfully applied to various sensors, including electrometers, current sensors, and accelerometers. The Chinese invention patent application with application number CN202310806821.3 proposes a modal localization electrometer based on self-adjustment of the modal coupling frequency, which uses electrostatic force to achieve coupling between resonant beams and realize flexible coupling strength control. With the greatly expanded linear working bandwidth, the measurement accuracy, range and other indicators of the electrometer based on the modal localization principle are significantly improved. To a certain extent, the problem of insufficient sensor measurement range has been solved. However, due to the high heat loss of the sensitive structure of the sensor, the improvement of sensitivity and quality factor is limited, and the requirements of high performance have not yet been met. In 2022, Chang Honglong's team from Northwestern Polytechnical University proposed a mode-localized DC electric field sensor based on a weakly coupled resonant system in the paper "A mode-localized DC electric field sensor". The sensor uses a designed capacitor array to sense the electric field and generate stiffness disturbances on the resonator, triggering the mode localization phenomenon, causing the resonator amplitude ratio to change, and achieving accurate measurement of the electric field, which to a certain extent solves the sensitivity and resolution problems of MEMS sensors. However, due to the limitations of the structural design of the resonator itself and the electric field transduction mechanism, it is still impossible to achieve a wider range and high quality factor under low vacuum, which limits the application of lightning detection in the meteorological field and also poses severe challenges to vacuum packaging. Summary of the invention

[0004] The present invention provides a weakly coupled double-end tuning fork MEMS electric field sensor to solve the technical problems of insufficient sensitivity, resolution, range and other performances of existing MEMS electric field sensors.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A weakly coupled double-ended tuning fork MEMS electric field sensor, comprising a ceramic package tube shell and a silicon-on-insulator resonator chip interconnected by gold wire bonding; the resonator chip is provided with a first resonator, a second resonator, a weakly coupled mechanical beam, a first mass block, a second mass block, a driving electrode, a DC bias electrode, a perturbation electrode, an adjustment electrode, a first sensing electrode and a second sensing electrode; wherein,

[0007] The first resonator and the second resonator are arranged in parallel and staggered in the horizontal direction on the same horizontal plane, and the two resonators overlap to a certain extent in the horizontal direction, and are connected by the weak coupling mechanical beam at the overlapping part;

[0008] In the vertical direction, the driving electrode and the first sensing electrode are respectively arranged on both sides of the first resonator, and the driving electrode and the first sensing electrode are arranged in parallel, the perturbation electrode and the second sensing electrode are respectively arranged on both sides of the second resonator, and the perturbation electrode and the second sensing electrode are arranged in parallel; in the horizontal direction, the DC bias electrode and the adjustment electrode are respectively arranged on both sides of the second resonator;

[0009] Along the vertical direction, the first mass blocks are respectively disposed on both sides of the first resonator, and the second mass blocks are respectively disposed on both sides of the second resonator.

[0010] Furthermore, a parallel plate capacitor is formed between the driving electrode and the first resonator, and an AC driving signal is applied to the driving electrode, the first resonator is periodically excited through the driving electrode, and energy is transferred through the weakly coupled mechanical beam to drive the second resonator, thereby achieving the purpose of driving the entire sensor;

[0011] The DC bias electrode is directly mechanically connected to the second resonator, and a DC voltage is applied to the DC bias electrode so that a stable potential difference exists between the DC bias electrode and the disturbance electrode;

[0012] The disturbance electrode is connected to the input electrode in the electric field to be measured through a wire, and a parallel plate capacitor is formed between the disturbance electrode and the second resonator. The electric field to be measured is converted into a redistribution of charges on the disturbance electrode by using the principle of electrostatic induction, and a negative electrostatic stiffness disturbance is generated on the second resonator, triggering a modal localization effect, thereby causing a redistribution of energy between modes, affecting the amplitude ratio of the second resonator, and achieving the purpose of detecting the electric field by measuring the changes in the amplitude and phase of the first resonator and the second resonator and calculating the amplitude ratio;

[0013] A parallel plate capacitor is formed between the adjustment electrode and the second resonator, and a fixed voltage is applied to the adjustment electrode through a DC power supply to adjust the stiffness of the second resonator so that the second resonator is located in an amplitude ratio sensitivity linear region outside the steering region;

[0014] The first sensing electrode and the first resonator form a parallel plate capacitor for detecting the amplitude of the first resonator; the second sensing electrode and the second resonator form a parallel plate capacitor for detecting the amplitude of the second resonator; the amplitude and phase information of the first resonator and the second resonator are obtained by measuring the change of the capacitance;

[0015] Among them, the length of all electrodes is 200~300μm, the width is 200~300μm, and the thickness is 20~40μm; and the gap of all parallel plate capacitors is 2~4μm.

[0016] Furthermore, the first resonator and the second resonator have the same shape and size, and are both double-ended fixed tuning fork structures; the double-ended fixed tuning fork structure consists of a rectangular resonant beam and a rectangular frame fixed at both ends of the rectangular resonant beam; the rectangular resonant beam has a length of 300~400μm, a width of 2~4μm, and a thickness of 20~40μm.

[0017] Furthermore, the double-ended fixed tuning fork structure adopts a connection design with an intermediate interval; and a hollow structure design.

[0018] Furthermore, the double-end fixed tuning fork structure adopts an annular or partially annular design.

[0019] Further, the first resonator and the second resonator differ in geometric structure and / or mass distribution.

[0020] Furthermore, the weakly coupled mechanical beam is a rectangular coupled beam with a length of 100-500 μm, a width of 1-5 μm, and a thickness of 20-40 μm; and the distances from the center point of the weakly coupled mechanical beam to the first resonator and the second resonator are equal.

[0021] Furthermore, the weakly coupled mechanical beam is a ring-shaped coupling beam.

[0022] Further, the first mass block includes a rectangular connection block perpendicular to the axial direction of the first resonator and a rectangular connection block parallel to the axial direction of the first resonator; and the first mass blocks on both sides of the first resonator are symmetrically arranged;

[0023] The second mass block includes a rectangular connecting block perpendicular to the axial direction of the second resonator and a rectangular connecting block parallel to the axial direction of the second resonator; and the second mass blocks on both sides of the second resonator are symmetrically arranged.

[0024] Furthermore, both the first mass block and the second mass block adopt a circular structural design, and the first mass blocks on both sides of the first resonator are asymmetrically arranged, and the second mass blocks on both sides of the second resonator are asymmetrically arranged.

[0025] The beneficial effects brought about by the technical solution provided by the present invention include at least:

[0026] (1) The present invention is a high-resolution, wide-range weak-coupling double-ended tuning fork MEMS electric field sensor based on modal localization. The double-ended tuning fork structural design is adopted. Two double-ended tuning fork resonators are placed in parallel and offset to the left and right on the same horizontal plane. While ensuring the structural stability, the middle part of the beam can vibrate freely, so that the double-ended tuning fork resonator exhibits a high-quality factor resonance characteristic at a specific frequency, thereby reducing heat loss and compensating for the reduction of the quality factor caused by parasitic feedthrough capacitance.

[0027] (2) The present invention can also adopt an intermediate spacer connection design and introduce microstructures, such as microgrooves, microholes, microgrooves, or design the beam into a honeycomb shape, so that the coupling stiffness between the resonators is much smaller than the coupling stiffness inside the tuning fork while ensuring that a high quality factor can be obtained, thereby avoiding the mode aliasing phenomenon and ensuring that the mode localization phenomenon mainly occurs between the two double-ended tuning fork resonators, and obtaining a better sensitivity, measurement range and quality factor;

[0028] (3) The two resonators of the present invention are coupled by a rectangular slender beam, and the aspect ratio of the slender beam is usually designed to be large, which ensures the weak coupling characteristics between the two double-ended tuning forks. Compared with the resonators with electrical coupling and mechanical coupling, it is more stable and has higher reliability;

[0029] (4) The present invention adopts a parallel plate capacitor structure to effectively transmit the sensor input and output signals. The parallel plate capacitor structure has a simple design and a mature manufacturing process, which helps to reduce production costs and improve product consistency. Since the capacitance value of the parallel plate capacitor is inversely proportional to the square of the distance between the electrodes, it has high stability and low environmental sensitivity, so that it can maintain excellent performance under different environmental conditions.

[0030] (5) The present invention adopts a single-ended driving method to periodically excite the first resonator by driving the electrode, thereby reducing the number of electrodes required and the complexity of chip design. In addition, compared with double-ended driving, higher amplitude ratio sensitivity can be achieved.

[0031] (6) The present invention uses capacitive sensing for detection, and by applying a fixed bias voltage on the resonator, signal detection is made easier, thereby obtaining a higher signal-to-noise ratio and lower noise performance;

[0032] (7) The input electrode of the present invention is located in the electric field to be measured, and the potential on the connected disturbance electrode is changed by electrostatic induction, so that the electric field is converted into a stiffness disturbance of the second resonator. The resonator is regulated by adjusting the voltage applied by the electrode, so that the working mode is in a high-sensitivity linear region, and the measurement range is also expanded;

[0033] (8) The structural size design of the present invention achieves a high quality factor in a low vacuum environment, reducing the requirements for high vacuum packaging;

[0034] (9) The present invention uses SOI wafer as the manufacturing material, which has high compatibility with MEMS technology, simple manufacturing and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 1 is a schematic diagram of the structure of a weakly coupled double-ended tuning fork MEMS electric field sensor provided by an embodiment of the present invention;

[0037] Figure 2 1 is a working principle diagram of a weakly coupled double-ended tuning fork MEMS electric field sensor provided by an embodiment of the present invention;

[0038] Figure 3 is a response curve diagram of a weakly coupled double-ended tuning fork MEMS electric field sensor to an electric field provided by an embodiment of the present invention;

[0039] Figure 4 It is the relationship between the resonator amplitude and frequency during the process of modal localization phenomenon under different stiffness disturbances of the weakly coupled double-ended tuning fork MEMS electric field sensor provided by an embodiment of the present invention; wherein (a) is the relationship between the amplitude and frequency of the first resonator; and (b) is the relationship between the amplitude and frequency of the second resonator.

[0040] Description of reference numerals:

[0041] 1. First resonator; 2. Second resonator; 3. Weakly coupled mechanical beam; 4. First mass block;

[0042] 5. Second mass block; 6. Driving electrode; 7. DC bias electrode; 8. Perturbation electrode;

[0043] 9. Adjustment electrode; 10. First sensing electrode; 11. Second sensing electrode. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0045] First of all, it should be noted that in the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "exemplarily" is intended to present the concept in a concrete way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0046] This embodiment provides a high-resolution, wide-range weak-coupled double-end tuning fork MEMS electric field sensor based on modal localization, which is a MEMS electric field sensor that can maximize the resolution and measurement range. The MEMS electric field sensor includes a ceramic package shell and a silicon-on-insulator (SOI) resonator chip. The chip and the package shell are interconnected by gold wire bonding, which effectively transmits the input and output signals of the resonator and facilitates the stable vibration of the resonator. Among them, the ceramic shell includes a ceramic cavity base with 44 gold-plated metal pins and a metal cover plate; the SOI resonator chip consists of a device layer, a buried oxide layer and a substrate layer, which is used to make a resonant electric field sensitive unit; wherein, the SOI resonator chip needs to go through a complete set of SOI etching processes starting from the SOI wafer: first, a metal pad is deposited on the device layer and patterned using a lift-off technique; second, the device layer is patterned by photolithography and coated with a layer of polyimide to protect its surface; then, deep silicon etching is performed to pattern the buried silicon layer to ensure the accuracy and integrity of the structure; Finally, hydrofluoric acid is used to wet-etch the silicon oxide of the buried oxide layer to release the device layer and remove the top polyimide protective layer. The materials used for the device layer and the substrate layer in the SOI resonator chip are both single crystal silicon, thereby ensuring the mechanical strength and stability of the structure, while the material used for the buried oxide layer in the SOI resonator chip is silicon oxide, which provides good electrical isolation and structural support. This process is mature and reliable, and can effectively manufacture high-precision MEMS electric field sensors, verifying the feasibility of the designed structure, while ensuring the stable performance of the device under high resolution and wide range.

[0047] like Figure 1 As shown, the device layer is provided with a first resonator 1, a second resonator 2, a weakly coupled mechanical beam 3, a first mass block 4, a second mass block 5, a driving electrode 6, a DC bias electrode 7, a disturbance electrode 8, an adjustment electrode 9, a first sensing electrode 10 and a second sensing electrode 11; the metal pads on the electrodes are connected to the packaging tube shell by gold wire bonding, so as to achieve the purpose of effectively transmitting the sensor input and output signals.

[0048] The first resonator 1 and the second resonator 2 are arranged in parallel and staggered in the horizontal direction (i.e., the left-right direction) on the same horizontal plane. While ensuring the stability of the structure, the middle part of the beam can vibrate freely, so that the double-ended tuning fork resonator exhibits a high-quality factor resonance characteristic at a specific frequency based on the modal localization effect; and the first resonator 1 and the second resonator 2 have a certain overlap in the horizontal direction, and the two resonators are connected by the weak coupling mechanical beam 3 at the overlapping part to form a weak coupling.

[0049] Furthermore, the first resonator 1 and the second resonator 2 can be designed with a symmetrical structure. The two can be exactly the same in geometric structure and size parameters, and both are double-ended tuning fork structures to ensure that the natural frequencies and modal shapes of the two are completely consistent when not disturbed. This design puts the system in the steering zone of modal localization. When the system is subjected to a slight disturbance, the modal localization phenomenon can be clearly observed without the need for additional adjustment or searching for the steering zone, thereby improving the detection accuracy and system stability.

[0050] Specifically, the double-ended fixed tuning fork structure consists of a rectangular resonant beam and a rectangular frame fixed at both ends of the rectangular resonant beam to reduce heat loss and compensate for the reduction in quality factor caused by parasitic feed-through capacitance; wherein the rectangular resonant beam has a length of 300~400μm, a width of 2~4μm, and a thickness of 20~40μm. In addition, the double-ended fixed-end tuning fork structure can also adopt an intermediate spacer connection design, which ensures that a high quality factor can be obtained while making the coupling stiffness between the resonators much smaller than the coupling stiffness inside the tuning fork, avoiding modal aliasing, and ensuring that the modal localization phenomenon mainly occurs between the two double-ended tuning fork resonators, which can clearly and effectively demonstrate the modal localization phenomenon; based on the connection of the intermediate spacer of the tuning fork, microstructures such as microgrooves, microholes, microgrooves or the beam can be designed into a honeycomb shape to reduce heat loss, frequency drift caused by thermal effects and energy loss and the influence of environmental changes, and obtain better sensitivity and quality factor; in addition, the tuning fork can also adopt an annular or partially annular design, thereby utilizing the continuity and integrity of the annular structure to reduce stress concentration and improve the frequency stability and resonance characteristics of the tuning fork.

[0051] In addition, the first resonator 1 and the second resonator 2 can also adopt an asymmetric structural design, and there are differences between the two in geometric structure and / or mass distribution. This structural design makes the initial state of the system in the linear region of amplitude ratio sensitivity (asymmetric state), so that the sensor can obtain higher sensitivity.

[0052] Among them, the weakly coupled mechanical beam 3 can adopt a rectangular slender beam with a length of 100~500μm, a width of 1~5μm, and a thickness of 20~40μm; the aspect ratio of the slender beam is usually designed to be large, ensuring the weak coupling characteristics between the two double-ended tuning forks, so that the system can clearly show the modal localization effect, and the distance from the center point of the slender beam to the two resonators is equal, ensuring the symmetry and uniformity of the system; in addition, the weakly coupled mechanical beam 3 can also adopt the structural design of an annular coupling beam, which can achieve an ultra-low coupling coefficient, ensure stable vibration modes and effective modal localization, and effectively avoid modal aliasing, so as to obtain a higher modal localization amplitude ratio sensitivity and improve the overall performance of the sensor.

[0053] Further, in the vertical direction, the driving electrode 6 and the first sensing electrode 10 are respectively arranged on both sides of the first resonator 1, and the driving electrode 6 and the first sensing electrode 10 are arranged in parallel, the perturbation electrode 8 and the second sensing electrode 11 are respectively arranged on both sides of the second resonator 2, and the perturbation electrode 8 and the second sensing electrode 11 are arranged in parallel; in the horizontal direction, the DC bias electrode 7 and the adjustment electrode 9 are respectively arranged on both sides of the second resonator 2; wherein the metal pads on the electrodes are interconnected with the package shell by gold wire bonding; the driving electrode 6, the perturbation electrode 8, the adjustment electrode 9, the first sensing electrode 10 and the second sensing electrode 11 are all coupled with the corresponding resonator by a parallel plate capacitor structure, so as to effectively transmit the input and output signals of the sensor, and the structure is simple in design and mature in manufacturing process, which helps to reduce production costs and improve product consistency, and has high stability and low environmental sensitivity.

[0054] Specifically, a parallel plate capacitor is formed between the driving electrode 6 and the first resonator 1. The sensor adopts a single-ended driving method. A periodic AC driving signal is applied to the driving electrode 6 to periodically excite the first resonator 1 through the parallel plate capacitor to drive the first resonator 1, and energy is transferred through the weakly coupled mechanical beam 3 to drive the second resonator 2, thereby achieving the purpose of driving the entire sensor.

[0055] The DC bias electrode 7 is directly mechanically connected to the second resonator 2 , and a DC voltage is applied to the DC bias electrode 7 so that a stable potential difference exists between the DC bias electrode 7 and the disturbance electrode 8 .

[0056] The disturbance electrode 8 is connected to the input electrode responsible for inducing the electric field in the electric field to be measured through a wire, and forms a parallel plate capacitor with the second resonator 2. By utilizing the principle of electrostatic induction, the electric field to be measured can be effectively converted into a redistribution of the charge on the disturbance electrode 8, and a negative electrostatic stiffness disturbance is generated on the second resonator 2, thereby achieving the purpose of converting the electric field to be measured into the stiffness disturbance of the resonator, triggering the modal localization effect, and then leading to the redistribution of energy between modes. The modal localization amplitude ratio changes, affecting the amplitude ratio of the second resonator 2, and the purpose of detecting the electric field is achieved by measuring the changes in the amplitude and phase of the first resonator 1 and the second resonator 2 and calculating the amplitude ratio.

[0057] A parallel plate capacitor is formed between the adjustment electrode 9 and the second resonator 2. A fixed voltage is applied to the adjustment electrode 9 through a DC power supply to generate a stiffness disturbance on the stiffness of the second resonator 2, which is used to adjust the stiffness and the initial working point of the second resonator 2 so that it is located in the amplitude ratio sensitivity linear region outside the steering region.

[0058] The first sensing electrode 10 and the first resonator 1 form a parallel plate capacitor, and the second sensing electrode 11 and the second resonator 2 form a parallel plate capacitor. With the DC bias, an open-loop measurement circuit is used to characterize the amplitude-frequency response of the two resonators in the sensor. The amplitude and phase information of the first resonator 1 and the second resonator 2 are obtained by measuring the change in capacitance; and the amplitude ratio of the resonators is obtained by calculation.

[0059] Among them, the length of all electrodes is 200~300μm, the width is 200~300μm, and the thickness is 20~40μm; the metal pad on the electrode is a rectangular structure with the same shape as the electrode but slightly smaller, and its side length is 150~250μm; the gap of the parallel plate capacitor between the resonator and the electrode is 2~4μm.

[0060] Furthermore, along the vertical direction, the first mass blocks 4 are respectively disposed on both sides of the first resonator 1 , and the second mass blocks 5 are respectively disposed on both sides of the second resonator 2 .

[0061] Among them, the first mass block 4 and the second mass block 5 have the same shape and size, the first mass block 4 includes a rectangular connecting block perpendicular to the axial direction of the first resonator 1 and a rectangular connecting block parallel to the axial direction of the first resonator 1, one end of the rectangular connecting block perpendicular to the axial direction of the first resonator 1 is connected to the first resonator 1, and the other end is connected to the rectangular connecting block parallel to the axial direction of the first resonator 1; and the first mass blocks 4 on both sides of the first resonator 1 are symmetrical about the long axis of the tuning fork; the second mass block 5 includes a rectangular connecting block perpendicular to the axial direction of the second resonator 2 and a rectangular connecting block parallel to the axial direction of the second resonator 2, one end of the rectangular connecting block perpendicular to the axial direction of the second resonator 2 is connected to the second resonator 2, and the other end is connected to the rectangular connecting block parallel to the axial direction of the second resonator 2, and the second mass blocks 5 on both sides of the second resonator 2 are symmetrical about the long axis of the tuning fork. This symmetrical layout optimizes the mass distribution and enhances the symmetry and stability of the resonator.

[0062] Furthermore, the first mass block 4 and the second mass block 5 can also adopt a circular structural design, and achieve an asymmetric structural design by changing the position of the mass block on the tuning fork. This structure can make the initial state of the sensor located in the linear region of amplitude ratio sensitivity, thereby obtaining better sensitivity performance.

[0063] Furthermore, the MEMS electric field sensor is fixed on a front-end amplifying circuit for effectively transmitting the input and output signals of the sensor; the front-end amplifying circuit includes a transimpedance amplifier, a DC decoupling capacitor and a voltage amplifier; the transimpedance amplifier is used to convert the weak current signal of the sensor into a voltage signal to improve the anti-interference ability of the signal; the DC decoupling capacitor is used to remove the DC bias in the signal to ensure that only the effective sensor output component is further amplified; the voltage amplifier is used to perform secondary amplification of the output signal to facilitate subsequent signal processing and precise measurement.

[0064] Based on the structural design of the double-ended tuning fork described above, this embodiment greatly broadens the range of the resonant sensor, improves the measurement resolution, achieves a high quality factor under low vacuum conditions, and overcomes the problem that the sensitivity of the resonant electric field sensor is in a nonlinear range. Based on the high quality factor under low vacuum conditions, the requirements of the resonant sensor for vacuum packaging are reduced; based on the above performance, the sensor can meet the actual application requirements of the wide range of resonant MEMS electric field sensors, and achieves a significant improvement in the overall performance of the modal localization sensor.

[0065] See also Figure 2 The MEMS electric field sensor of this embodiment adopts an open-loop characterization circuit, and the AC signal V ac and DC bias voltage V dc , generating periodic electrostatic excitation to make the sensor vibrate periodically; in conjunction with the adjustment voltage V t , adjust the sensor sensitivity to be within the linear region; due to electrostatic induction, the electric field is converted into the disturbance of the second resonator, causing the amplitude of the two resonators to change; the change in amplitude means that the induced current induced by the two sensing electrodes changes, and the induced current passes through the transimpedance amplifier of the front-end amplifier circuit, converting the current signal into a voltage signal with strong anti-interference ability, and then the signal is further amplified by the voltage amplifier of the preamplifier circuit, thereby improving the signal-to-noise ratio of the voltage signal and facilitating reading; after a series of signal processing such as mixers, phase detectors, filters and amplifiers, the amplitudes and phases of the two resonators are obtained respectively.

[0066] See also Figure 3 , which is an amplitude-frequency response diagram of the MEMS electric field sensor of this embodiment, when the resonator transfers from a balanced state to a non-equilibrium state after an electric field disturbance is applied.

[0067] See also Figure 4, which is the MEMS electric field sensor of this embodiment, by applying different electric field strengths, the amplitude-frequency responses of the two resonators under different relative disturbances are obtained; it can be seen that as the relative disturbance increases, the first mode amplitude of the first resonator decreases, and the second mode amplitude increases; the two mode amplitudes of the second resonator both decrease. This means that the mode localization phenomenon occurs, and the energy is transferred to the first mode of the first resonator.

[0068] In summary, this embodiment provides a high-resolution, wide-range weak-coupled double-ended tuning fork MEMS electric field sensor based on modal localization. The sensor is based on the modal localization mechanism of the weak-coupled resonant system and utilizes the electrostatic induction principle of the metal electrode to convert the measured electric field into the stiffness disturbance of the resonator, triggering the modal localization phenomenon, resulting in the redistribution of energy between the modes of the resonant system, and using the dimensionless amplitude ratio as output, thereby achieving an improvement in sensitivity and, to a certain extent, achieving the effect of resisting temperature drift. The sensor is designed with two double-ended tuning fork resonators coupled by a mechanical beam to reduce heat loss and compensate for the reduction in quality factor caused by parasitic feed-through capacitance; by converting the electric field into a negative electrostatic stiffness disturbance of the resonator, the modal localization effect is triggered, thereby affecting the amplitude ratio of the resonator, achieving superior performance of high quality factor and wide range. Open-loop and closed-loop experiments were performed on two double-ended tuning fork resonators with the above-mentioned structural dimensions to characterize them. Under weak coupling conditions, based on the structural design and modal localization effect, the harmonic sensor achieved a comprehensive and substantial improvement in performance, such as wide range, high resolution, and high quality factor under low vacuum. This proves that the sensor has an excellent quality factor under low vacuum conditions, which reduces the requirements for high vacuum packaging. Combined with the characteristics that the initial state of the resonator is in the linear region, the resolution and range of the sensor are significantly improved.

[0069] In addition, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device.

[0070] In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements. In addition, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship, but it may also represent an "and / or" relationship, which can be understood by referring to the context. "At least one" means one or more, and "multiple" means two or more. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple.

[0071] Finally, it should be noted that the above is only a preferred embodiment of the present invention. It should be pointed out that although the preferred embodiment of the present invention has been described, for ordinary technicians in this technical field, once the basic creative concept of the present invention is known, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. Therefore, the attached claims are intended to be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the embodiments of the present invention.

Claims

1. A weakly coupled double-ended tuning fork MEMS electric field sensor, comprising a ceramic package tube shell and a silicon-on-insulator resonator chip interconnected by gold wire bonding; characterized in that: The resonator chip is provided with a first resonator, a second resonator, a weakly coupled mechanical beam, a first mass block, a second mass block, a driving electrode, a DC bias electrode, a disturbance electrode, an adjustment electrode, a first sensing electrode and a second sensing electrode; wherein, The first resonator and the second resonator are arranged in parallel and staggered in the horizontal direction on the same horizontal plane, and the two resonators overlap to a certain extent in the horizontal direction, and are connected by the weak coupling mechanical beam at the overlapping part; In the vertical direction, the driving electrode and the first sensing electrode are respectively arranged on both sides of the first resonator, and the driving electrode and the first sensing electrode are arranged in parallel, the perturbation electrode and the second sensing electrode are respectively arranged on both sides of the second resonator, and the perturbation electrode and the second sensing electrode are arranged in parallel; in the horizontal direction, the DC bias electrode and the adjustment electrode are respectively arranged on both sides of the second resonator; Along the vertical direction, the first mass blocks are respectively disposed on both sides of the first resonator, and the second mass blocks are respectively disposed on both sides of the second resonator.

2. The weakly coupled double-ended tuning fork MEMS electric field sensor according to claim 1, characterized in that: A parallel plate capacitor is formed between the driving electrode and the first resonator. By applying an AC driving signal to the driving electrode, the first resonator is periodically excited through the driving electrode, and energy is transferred through the weakly coupled mechanical beam to drive the second resonator, thereby achieving the purpose of driving the entire sensor; The DC bias electrode is directly mechanically connected to the second resonator, and a DC voltage is applied to the DC bias electrode so that a stable potential difference exists between the DC bias electrode and the disturbance electrode; The disturbance electrode is connected to the input electrode in the electric field to be measured through a wire, and a parallel plate capacitor is formed between the disturbance electrode and the second resonator. The electric field to be measured is converted into a redistribution of charges on the disturbance electrode by using the principle of electrostatic induction, and a negative electrostatic stiffness disturbance is generated on the second resonator, triggering a modal localization effect, thereby causing a redistribution of energy between modes, affecting the amplitude ratio of the second resonator, and achieving the purpose of detecting the electric field by measuring the changes in the amplitude and phase of the first resonator and the second resonator and calculating the amplitude ratio; A parallel plate capacitor is formed between the adjustment electrode and the second resonator, and a fixed voltage is applied to the adjustment electrode through a DC power supply to adjust the stiffness of the second resonator so that the second resonator is located in an amplitude ratio sensitivity linear region outside the steering region; The first sensing electrode and the first resonator form a parallel plate capacitor for detecting the amplitude of the first resonator; The second sensing electrode and the second resonator form a parallel plate capacitor for detecting the amplitude of the second resonator; the amplitude and phase information of the first resonator and the second resonator are obtained by measuring the change of the capacitance; Among them, the length of all electrodes is 200~300μm, the width is 200~300μm, and the thickness is 20~40μm; and the gap of all parallel plate capacitors is 2~4μm.

3. The weakly coupled double-ended tuning fork MEMS electric field sensor according to claim 1, characterized in that: The first resonator and the second resonator have the same shape and size, and are both double-ended fixed tuning fork structures; the double-ended fixed tuning fork structure consists of a rectangular resonant beam and a rectangular frame fixed at both ends of the rectangular resonant beam; the rectangular resonant beam has a length of 300~400μm, a width of 2~4μm, and a thickness of 20~40μm.

4. The weakly coupled double-ended tuning fork MEMS electric field sensor according to claim 3, characterized in that: The double-end fixed tuning fork structure adopts a connection design with an intermediate interval; and also adopts a hollow structure design.

5. The weakly coupled double-ended tuning fork MEMS electric field sensor according to claim 3, characterized in that: The double-end fixed tuning fork structure adopts an annular or partially annular design.

6. The weakly coupled double-ended tuning fork MEMS electric field sensor according to claim 1, characterized in that: The first resonator and the second resonator differ in geometric structure and / or mass distribution.

7. The weakly coupled double-ended tuning fork MEMS electric field sensor according to claim 1, characterized in that: The weakly coupled mechanical beam is a rectangular coupled beam with a length of 100-500 μm, a width of 1-5 μm, and a thickness of 20-40 μm; and the distances from the center point of the weakly coupled mechanical beam to the first resonator and the second resonator are equal.

8. The weakly coupled double-ended tuning fork MEMS electric field sensor according to claim 1, characterized in that: The weakly coupled mechanical beam is a ring-shaped coupling beam.

9. The weakly coupled double-ended tuning fork MEMS electric field sensor according to claim 1, characterized in that: The first mass block includes a rectangular connecting block perpendicular to the axial direction of the first resonator and a rectangular connecting block parallel to the axial direction of the first resonator; and the first mass blocks on both sides of the first resonator are symmetrically arranged; The second mass block includes a rectangular connecting block perpendicular to the axial direction of the second resonator and a rectangular connecting block parallel to the axial direction of the second resonator; and the second mass blocks on both sides of the second resonator are symmetrically arranged.

10. The weakly coupled double-ended tuning fork MEMS electric field sensor according to claim 1, characterized in that: The first mass block and the second mass block both adopt a circular structure design, and the first mass blocks on both sides of the first resonator are asymmetrically arranged, and the second mass blocks on both sides of the second resonator are asymmetrically arranged.

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