A differential micro electric field sensor based on frequency output and a working method thereof

Abstract

The application discloses a frequency output-based differential micro electric field sensor and a working method thereof, and relates to the field of sensors.The sensor comprises a resonant beam structure, an input structure, a driving structure and an output structure, the resonant beam structure has at least one pair of left-right symmetrical and vibrationable extension vertical beams; the input structure comprises a fixed input electrode, an input coupling unit is arranged between the fixed input electrode and the adjacent extension vertical beam, and an external sensing metal plate is connected to the fixed input electrode, the external sensing metal plate can be placed in a to-be-detected electric field; the driving structure comprises a fixed driving electrode and a driving coupling unit; the output structure comprises at least two output units, which are arranged on both sides of the extension vertical beams away from the input structure and the driving structure; and each output unit comprises a fixed output electrode. The frequency output-based differential micro electric field sensor and the working method thereof have high detection sensitivity, the output signal is represented by a resonant frequency, and the output signal is convenient for analysis in the rear end.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a differential micro electric field sensor based on frequency output and its operating method. Background Technology

[0002] Electric field sensors are core components for detecting electric field intensity and characterizing spatial electric field distribution. They are widely used in key areas such as electrostatic protection for aerospace vehicles, electromagnetic situational awareness for defense equipment, meteorological and lightning warnings, voltage monitoring and equipment insulation fault diagnosis in smart grids, electrostatic protection in industrial production, and basic physical science research. In smart grids and ultra-high voltage and extra-high voltage direct current transmission projects, electric field distribution inversion enables non-contact conductor voltage measurement and online assessment of equipment insulation status, which is a core technology for improving the safety and reliability of power system operation. In equipment operation and battlefield electromagnetic situational awareness under complex electromagnetic environments, highly sensitive and highly anti-interference miniature electric field sensors are key supporting components for realizing the digitization and visualization of the electromagnetic environment.

[0003] Driven by the continuous advancements in microelectronics, microfabrication, and ultra-precision machining technologies, electric field sensors based on MEMS (Micro-Electro-Mechanical Systems) technology are gradually replacing traditional mechanical and optical electric field sensors, becoming the most promising technology in the field of electric field detection due to their significant advantages such as small size, low power consumption, low manufacturing cost, ease of integration with integrated circuits, and mass production capability. Currently, MEMS electric field sensors mainly achieve electric field detection based on principles such as electrostatic induction, piezoelectric effect, and resonant modulation. Among them, resonant MEMS electric field sensors measure electric field signals by converting them into the inherent frequency shift of a resonant structure, exhibiting high detection sensitivity and long-term stability, and have become a key focus of current academic research and industrialization.

[0004] However, existing resonant MEMS electric field sensors still suffer from numerous technical shortcomings in practical engineering applications, severely hindering their widespread application in high-precision, highly interference-prone, and complex scenarios. First, most existing sensors employ a single-ended output structure, which cannot effectively suppress common-mode interference signals such as temperature drift, power supply voltage fluctuations, mechanical vibration, and environmental electromagnetic noise. This makes measurement results susceptible to environmental factors, resulting in insufficient detection accuracy and long-term stability. Furthermore, the limited signal amplitude of the single-ended output structure further restricts the sensor's ability to detect weak electric field signals. Second, existing devices primarily rely on analog voltage or current signal output. The original signal generated by the electric field is extremely weak and highly susceptible to external electromagnetic interference during transmission and processing. This necessitates complex signal conditioning, multi-stage amplification, and analog-to-digital conversion circuits, significantly increasing system power consumption, size, and overall cost. It also introduces additional circuit noise, ultimately limiting further improvements in detection accuracy and hindering seamless integration with backend digital processing systems. Finally, in pursuit of miniaturization, the input capacitive coupling area of ​​existing sensors is generally designed to be small, resulting in low perturbation gain in the electric field-mechanical conversion process. The change in equivalent stiffness of the resonant structure caused by external electric field signals is limited, making it difficult to achieve high-sensitivity detection of weak electric field signals at the nanovolt level.

[0005] Therefore, there is an urgent need to design a technical solution with high detection sensitivity that can output the resonant frequency as a characteristic quantity. Summary of the Invention

[0006] The purpose of this invention is to provide a differential micro electric field sensor based on frequency output and its working method, so as to solve the problems existing in the prior art. It has high detection sensitivity and can output the resonant frequency as a characteristic quantity, which is convenient for back-end analysis.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a differential micro electric field sensor based on frequency output, comprising a resonant beam structure, an input structure, a driving structure, and an output structure. The resonant beam structure has at least one pair of left-right symmetrical, vibrating extended vertical beams. The input structure includes a fixed input electrode connected to a substrate via a fixed beam and positioned outside the outermost extended vertical beam. An input coupling unit is provided between the fixed input electrode and the adjacent extended vertical beam. An external sensing metal plate is externally connected to the fixed input electrode and can be placed in the electric field to be measured. The input coupling unit can introduce axial compressive or tensile stress into the resonant beam structure, causing a shift in the resonant frequency of the resonant beam structure. The driving structure includes a fixed driving electrode and a driving coupling unit. The fixed driving electrode is fixed to the substrate via a beam. The fixed driving electrode is located on the other side of the extended vertical beam adjacent to the fixed input electrode. A driving coupling unit is provided between the fixed driving electrode and the corresponding extended vertical beam. An excitation voltage can be applied to the fixed driving electrode to make the resonant beam structure resonate continuously through the driving coupling unit. The output structure includes at least two output units, symmetrically arranged on both sides of the vibration direction under the working mode of the extended vertical beam. Each output unit includes a fixed output electrode, which is fixed to the substrate through an output beam. An output coupling unit is provided between the fixed output electrode and the adjacent extended vertical beam. The output unit located on the same side of the vibration direction under the working mode of the extended vertical beam constitutes the first output terminal, and the output unit located on the other side of the vibration direction under the working mode of the extended vertical beam constitutes the second output terminal. The first output terminal and the second output terminal constitute a differential output terminal.

[0008] In one embodiment, the resonant beam structure further includes two parallel thin vertical beams and a horizontal beam connecting the two thin vertical beams; the upper ends of the two thin vertical beams are fixedly connected to a horizontally arranged upper support beam, and the lower ends of the two thin vertical beams are fixedly connected to a horizontally arranged lower support beam; the horizontal beam is vertically fixed at the middle position of the thin vertical beams; and the left and right ends of the horizontal beam extend horizontally away from the thin vertical beams respectively, the extended vertical beam is fixed on the horizontal beam and located outside the thin vertical beams, the extended vertical beam is rigidly connected to the horizontal beam and can vibrate synchronously with the thin vertical beams.

[0009] In one embodiment, the fixed input electrode is arranged parallel to the adjacent extended vertical beam, and the input coupling unit includes a fixed input comb beam disposed on one side of the fixed input electrode and a movable input comb beam disposed on the corresponding extended vertical beam. The fixed input comb beam and the corresponding movable input comb beam are arranged alternately to form an input capacitor comb pair.

[0010] In one embodiment, the fixed driving electrode is arranged parallel to the adjacent extended vertical beam. The driving coupling unit includes a fixed driving comb beam disposed on the fixed driving electrode and a movable driving comb beam disposed on the corresponding extended vertical beam. The fixed driving comb beam and the movable driving comb beam are staggered in the horizontal direction to form a driving capacitor comb pair. When an alternating driving voltage is applied, the driving capacitor comb pair generates a periodic electrostatic force to drive the resonant beam structure to resonate and vibrate.

[0011] In one embodiment, the fixed output electrode is arranged parallel to the adjacent extended vertical beam; the output coupling unit includes a fixed output comb beam disposed on the fixed output electrode and a movable output comb beam disposed on the corresponding extended vertical beam, the fixed output comb beam and the movable output comb beam are arranged alternately to form an output capacitor comb pair, which is used to convert the vibration displacement of the resonant beam structure into a change in output capacitance.

[0012] In one embodiment, both the fixed input comb beam and the movable input comb beam are arranged vertically so that adjacent fixed input comb beams and movable input comb beams are arranged in a horizontally staggered manner to form input capacitor comb pairs; or, both the fixed input comb beam and the movable input comb beam are arranged horizontally so that adjacent fixed input comb beams and movable input comb beams are arranged in a vertically staggered manner to form input capacitor comb pairs.

[0013] In one embodiment, four extending vertical beams are provided, namely a first extending vertical beam, a second extending vertical beam, a third extending vertical beam, and a fourth extending vertical beam; the first and second extending vertical beams are provided on the crossbeam located to the left of the thin vertical beam, and the third and fourth extending vertical beams are provided on the crossbeam located to the right of the thin vertical beam; a fixed input electrode is provided on the outer side of the first extending vertical beam and the outer side of the fourth extending vertical beam, and a fixed drive electrode is provided on the inner side of the first extending vertical beam and the inner side of the fourth extending vertical beam; a fixed output electrode is provided on the inner side of the second extending vertical beam and the inner side of the third extending vertical beam. Among the four output units, two output units arranged symmetrically on the left and right constitute a differential output structure; under the working mode of the resonant beam structure, the vibration directions of the extending vertical beams on the left and right sides are opposite, so that the capacitance changes of the two output capacitor comb pairs in this differential output structure are similar in magnitude and opposite in direction, and the differential output signal is obtained by differential measurement of the two output terminals.

[0014] In one embodiment, there are two extending vertical beams, including a first extending vertical beam and a second extending vertical beam symmetrically arranged on the left and right sides of the thin vertical beam; a fixed input electrode is provided on the outer side of the first extending vertical beam, and a fixed driving electrode is provided on the inner side of the first extending vertical beam; the fixed output electrode is provided on both the inner and outer sides of the second extending vertical beam.

[0015] In one embodiment, the extended vertical beams located on the left and right sides of the resonant beam structure vibrate in opposite phases, so that the output capacitances of the first output terminal and the second output terminal change in opposite directions; the first output terminal and the second output terminal are respectively connected to transimpedance amplifiers, and the transimpedance amplifiers are connected to instrumentation amplifiers.

[0016] This invention provides a method for operating a differential miniature electric field sensor based on frequency output, comprising the following steps: When an external metal plate is placed in the electric field to be measured, an induced charge is generated on its surface; a fixed input electrode connected to it by a wire generates a proportionally opposite charge. The input capacitance formed between the fixed input comb beam on the fixed input electrode and the adjacent movable input comb beam generates an attractive force under the action of the electrostatic field, causing the movable input comb beam to deflect towards the fixed input comb beam, thereby introducing axial compressive or tensile stress into the resonant beam structure, changing its equivalent stiffness, and causing the resonant frequency to shift. An excitation voltage is applied to a fixed driving electrode to make the resonant beam structure resonate continuously at a frequency close to its intrinsic frequency. During the resonance process, the extended vertical beams on the left and right sides of the resonant beam structure vibrate in opposite phases, and the output capacitances of the first and second output terminals change in opposite directions. The fixed output electrodes are converted into high-frequency AC voltage signals by transimpedance amplifiers, and then differentially amplified by instrumentation amplifiers to obtain AC differential output voltages. The frequency change corresponding to the AC differential output voltage is detected to measure the electric field strength under test.

[0017] The present invention achieves the following technical effects compared to the prior art: The differential miniature electric field sensor based on frequency output of this invention designs fixed input electrodes, fixed drive electrodes, and fixed output electrodes as fixed electrodes, and forms multiple sets of capacitor structures in conjunction with a resonant beam structure. Under the action of an external electric field, electrostatic force is used to change the equivalent stiffness and resonant frequency of the resonant beam structure. The differential readout of the multi-channel output capacitors and the use of the resonant frequency as the output characteristic quantity realize frequency-type digital output. The differential output structure improves the common-mode rejection capability, and the use of the resonant frequency as the output characteristic quantity facilitates the backend to obtain the measurement results by frequency analysis. This not only achieves highly sensitive detection of electric field strength, but also significantly improves the anti-interference capability of the system. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the differential micro electric field sensor structure based on frequency output in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram illustrating the working principle of the differential micro electric field sensor based on frequency output in Embodiment 1 of the present invention. Figure 3 This is a schematic diagram of the comb electrode of the differential micro electric field sensor based on frequency output in Embodiment 1 of the present invention. Figure 4 This is a schematic diagram of the differential micro electric field sensor structure based on frequency output in Embodiment 2 of the present invention; Figure 5 This is a schematic diagram illustrating the working principle of the differential micro electric field sensor based on frequency output in Embodiment 2 of the present invention. Figure 6 This is a schematic diagram of the comb electrode of the differential micro electric field sensor based on frequency output in Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of a differential micro electric field sensor based on frequency output in Embodiment 3 of the present invention.

[0020] Figure reference numerals: 1-Resonant beam structure; 11-Horizontal beam; 112-First extended vertical beam; 113-Second extended vertical beam; 114-Third extended vertical beam; 115-Fourth extended vertical beam; 101-Upper support fixed beam; 102-Lower support fixed beam; 21-Left disturbance input electrode; 22-Right disturbance input electrode; 31-Upper left driving electrode; 32-Lower left driving electrode; 33-Upper right driving electrode; 34-Lower right driving electrode; 41-Upper left sensing output electrode; 42-Lower left sensing output electrode; 43-Upper right sensing output electrode; 44-Lower right sensing output electrode; 211-External sensing metal plate; 311-AC driving power supply; 312-Power ground; 411-Trans-resistor amplifier Large instrument; 412-Instrument amplifier; 51-Disturbance input electrode 2; 61-Upper drive electrode 1; 62-Lower drive electrode 1; 71-Resonant beam structure 2; 701-Upper support fixed beam 2; 702-Lower support fixed beam 2; 81-Upper left sensing output electrode 1; 82-Lower left sensing output electrode 1; 83-Upper right sensing output electrode 1; 84-Lower right sensing output electrode 1; 91-Resonant beam structure 3; 920-Upper support fixed beam 3; 921-Lower support fixed beam 3; 930-Input electrode 3; 931-Sensing output electrode 3; 940-Upper drive electrode 2; 941-Lower drive electrode 2; 950-Upper left sensing output electrode 3; 951-Lower left sensing output electrode 3. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The purpose of this invention is to provide a differential micro electric field sensor based on frequency output and its working method, so as to solve the problems existing in the prior art. It has high detection sensitivity and can output the resonant frequency as a characteristic quantity, which is convenient for back-end analysis.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] refer to Figures 1-7As shown, this invention provides a differential micro electric field sensor based on frequency output, including a resonant beam structure 1, an input structure, a driving structure, and an output structure. The resonant beam structure 1 has at least one pair of left-right symmetrical and vibrating extended vertical beams. The input structure includes a fixed input electrode, which is connected to the substrate via a fixed beam and is arranged outside the outermost extended vertical beam. An input coupling unit is provided between the fixed input electrode and the adjacent extended vertical beam. An external sensing metal plate 211 is externally connected to the fixed input electrode via a wire. The external sensing metal plate 211 can be placed in the electric field to be measured. The input coupling unit can introduce axial compressive or tensile stress into the resonant beam structure 1, causing a shift in the resonant frequency of the resonant beam structure 1. The driving structure includes a fixed driving electrode and a driving coupling unit. The fixed driving electrode is fixed to the substrate via a beam. On the other side of the extended vertical beam adjacent to the fixed input electrode, a drive coupling unit is provided between the extended vertical beams corresponding to the fixed drive electrode. The fixed drive electrode is connected to an AC drive power supply 311 through a wire so that an excitation voltage can be applied to the fixed drive electrode so that the resonant beam structure 1 can resonate continuously through the drive coupling unit. The output structure includes at least two output units, which are symmetrically arranged on both sides of the vibration direction under the working mode of the extended vertical beam. Each output unit includes a fixed output electrode, which is fixed to the base through an output beam. An output coupling unit is provided between the fixed output electrode and the adjacent extended vertical beam. The output unit located on the same side of the vibration direction under the working mode of the extended vertical beam constitutes the first output terminal, and the output unit located on the other side of the vibration direction under the working mode of the extended vertical beam constitutes the second output terminal. The first output terminal and the second output terminal constitute a differential output terminal. The resonant beam structure 1 also includes two parallel thin vertical beams and a horizontal beam 11 that connects the two thin vertical beams. The upper ends of the two thin vertical beams are fixedly connected to a horizontally arranged upper support fixing beam 101, and the lower ends of the two thin vertical beams are fixedly connected to a horizontally arranged lower support fixing beam 102. The lower support fixing beam 102 is connected to the power ground 312. The horizontal beam 11 is vertically fixed at the middle position of the thin vertical beams. The left and right ends of the horizontal beam 11 extend horizontally away from the thin vertical beams. The extended vertical beams are fixed on the horizontal beam 11 and located outside the thin vertical beams. In the resonant state, the two thin vertical beams undergo bending vibration in the plane. The horizontal beam 11 and its extended vertical beams are rigidly connected to the thin vertical beams and vibrate synchronously with the thin vertical beams.The differential miniature electric field sensor based on frequency output of the present invention designs the fixed input electrode, fixed driving electrode, and fixed output electrode as fixed electrodes, and forms multiple sets of capacitor structures in conjunction with the resonant beam structure 1. Under the action of an external electric field, the equivalent stiffness and resonant frequency of the resonant beam structure 1 are changed by electrostatic force. The frequency-type digital output is achieved by differential readout of the multi-channel output capacitor and using the resonant frequency as the output characterization quantity. The differential output structure improves the common-mode rejection capability, and the use of the resonant frequency as the output characterization quantity facilitates the back-end to obtain the measurement results by frequency analysis. This not only achieves high-sensitivity detection of electric field strength, but also significantly improves the anti-interference capability of the system.

[0025] Example 1 In this embodiment, four extension vertical beams are provided, namely, the first extension vertical beam 112, the second extension vertical beam 113, the third extension vertical beam 114, and the fourth extension vertical beam 115. The fixed input electrode is arranged parallel to the adjacent extension vertical beam. The input coupling unit includes a fixed input comb beam disposed on one side of the fixed input electrode and a movable input comb beam disposed on the corresponding extension vertical beam. The fixed input comb beam and the corresponding movable input comb beam are staggered to form an input capacitor comb pair. The fixed drive electrode is arranged parallel to the adjacent extension vertical beam. The drive coupling unit includes a fixed drive comb beam disposed on the fixed drive electrode and a movable drive comb beam disposed on the corresponding extension vertical beam. The fixed drive comb beam and the movable drive comb beam are staggered in the horizontal direction to form a drive capacitor comb pair. When an alternating drive voltage is applied through the AC drive power supply 311, the drive capacitor comb pair generates a periodic electrostatic force to drive the resonant beam structure 1 to resonate and vibrate. The fixed output electrode is arranged parallel to the adjacent extended vertical beam. The output coupling unit includes a fixed output comb beam disposed on the fixed output electrode and a movable output comb beam disposed on the corresponding extended vertical beam. The fixed output comb beam and the movable output comb beam are staggered to form an output capacitor comb pair, which is used to convert the vibration displacement of the resonant beam structure 1 into a change in output capacitance. Both the fixed input comb beam and the movable input comb beam are arranged vertically so that adjacent fixed comb beams and movable input comb beams are arranged laterally to form an input capacitor comb pair; or, both the fixed input comb beam and the movable input comb beam are arranged laterally so that adjacent fixed comb beams and movable input comb beams are arranged vertically to form an input capacitor comb pair.

[0026] In this embodiment, the resonant beam structure 1 and the comb teeth on its extended vertical beam are movable parts, which are anchored by the upper support fixed beam 101 and the lower support fixed beam 102. The remaining beams and comb teeth connected to each electrode are fixed parts.

[0027] In this embodiment, the input electrode structure includes two identical sets of input electrodes, defined as the left perturbation input electrode 21 and the right perturbation input electrode 22, respectively, arranged on the left and right sides of the resonant beam structure 1. For ease of explanation, unless otherwise specified, the right perturbation input electrode 22 will be used to represent the two sets of input electrode structures. The right perturbation input electrode 22 is connected to the substrate via a fixed beam. The fixed input comb beam on the right perturbation input electrode 22 meshes with the movable input comb beam on the first extended vertical beam 112 extending laterally from the resonant beam. The fixed input comb beam on the right perturbation input electrode 22 meshes with the movable input comb beam on the fourth extended vertical beam 115 extending laterally from the resonant beam, forming a vertical comb-shaped input capacitor structure. Figure 3 As shown, in the resonant operating state, the input movable comb beam vibrates laterally with the resonant beam structure 1, and the input capacitance changes accordingly, realizing the coupling of the external electric field signal to the resonant beam structure 1.

[0028] The driving electrode structure includes four identical fixed driving electrodes, defined as the coaxially arranged upper left driving electrode 31, lower left driving electrode 32, and coaxially arranged upper right driving electrode 33, lower right driving electrode 34, respectively positioned at the upper left, lower left, upper right, and lower right positions of the resonant beam structure 1. Figure 1 For example, the upper left driving electrode 31 and the lower left driving electrode 32 are arranged inside the first extended vertical beam 112, and the upper right driving electrode 33 and the lower right driving electrode 34 are arranged inside the fourth extended vertical beam 115. Unless otherwise specified, each fixed driving electrode is fixed to the base via its connecting beam. The fixed driving comb beams on the fixed driving electrode and the corresponding movable driving comb beams on the extended vertical beam are arranged alternately to form a transverse comb-shaped driving capacitor structure. In use, a DC voltage superimposed with an AC excitation voltage is applied to the fixed driving electrode, generating a time-varying electrostatic force in the driving capacitor structure, thereby exciting the resonant beam structure 1 to produce transverse resonant vibration, the vibration mode of which is as follows: Figure 3 As shown.

[0029] The output electrode structure also includes four identical fixed output electrodes, defined as the coaxially arranged upper left induction output electrode 41, lower left induction output electrode 42, and coaxially arranged upper right induction output electrode 43 and lower right induction output electrode 44, respectively, arranged adjacent to the four sets of drive electrode structures. The fixed output electrodes are connected to the base via fixed beams. The fixed output comb beams on the fixed output electrodes and the movable output comb beams on the extended vertical beam of the resonant beam structure 1 are staggered to form an output capacitor structure. During resonance, the overlap area between the movable output comb beams and the fixed output comb beams changes with the displacement of the resonant beam structure 1, thereby causing periodic changes in the output capacitance value, and the output induced current changes accordingly.

[0030] In this embodiment, to achieve differential output, the four fixed output electrodes are divided into left and right groups by the resonant beam structure 1. The two output electrode structures within each group exhibit the same output change direction during resonance. A pair of differential output terminals can be formed by selecting any one output electrode structure from the left or right groups. For example, the upper left induction output electrode 41 on the left and the upper right induction output electrode 43 on the right can be selected to form a pair of differential output terminals. To increase the output signal amplitude, two output electrode structures within the same group can be connected in parallel as a single electrode, forming a left parallel output electrode and a right parallel output electrode, which together form a pair of differential output terminals.

[0031] like Figure 1 and Figure 2 As shown, the sensor in this embodiment can be divided into a movable part and a fixed part. The movable part includes a resonant beam structure 1 and a horizontal beam, an extended vertical beam and movable comb teeth rigidly connected to it; the fixed part includes a fixed input electrode, a fixed drive electrode, a fixed output electrode and their connecting beams and fixed comb teeth, as well as an upper supporting fixed beam 101, a lower supporting fixed beam 102, etc. When an excitation is applied, the resonant beam structure 1 generates bending vibration in the plane, and the horizontal beam 11 and the extended vertical beam vibrate as a whole, realizing synchronous modulation of multiple capacitor units.

[0032] In this embodiment, the working principle of the resonant micro electric field sensor is as follows: Figure 2 As shown, an external metal plate is placed in the electric field E to be measured, and an induced charge -Q is generated on its surface. A fixed input electrode connected to it via a wire generates a proportionally opposite charge kQ, where k is a proportionality coefficient. The input capacitance formed between the fixed input comb beam on the fixed input electrode and the corresponding movable input comb beam on the resonant beam structure 1 generates an attractive force under the action of the electrostatic field, causing the movable input comb beam to deflect towards the fixed input comb beam. This introduces axial compressive or tensile stress into the resonant beam structure 1, changing its equivalent stiffness and shifting its resonant frequency. Simultaneously, an excitation voltage is applied to the fixed driving electrode, causing the resonant beam structure 1 to resonate continuously near its intrinsic frequency.

[0033] During the resonance process, such as Figure 3 As shown, the extended vertical beams on the left and right sides of the resonant beam structure 1 vibrate in opposite phases, causing the output capacitance in the two sets of output electrode structures to change in opposite directions. The fixed output electrodes are converted into high-frequency AC voltage signals by transimpedance amplifier 411, and then differentially amplified by instrumentation amplifier 412 to obtain AC differential output voltage. Differential readout can suppress common-mode noise and co-source interference. The output is characterized by the resonant frequency, which facilitates frequency analysis at the back end. By detecting the frequency change corresponding to the AC differential output voltage, high-precision measurement of the electric field strength under test can be achieved.

[0034] The input, driving, and output structures are all arranged symmetrically about the central axis of the resonant beam structure 1 to reduce the additional errors caused by structural asymmetry and further improve the common-mode rejection capability of the differential output. Both the fixed and movable comb beams in the input, driving, and output structures employ multi-finger comb structures to significantly increase the equivalent capacitance and its rate of change while maintaining a small device size, thereby improving coupling and modulation efficiency and ultimately enhancing the electro-mechanical conversion sensitivity.

[0035] Example 2 This embodiment is an improvement upon embodiment one, such as... Figures 4-6 As shown, in this embodiment, the resonant beam is defined as resonant beam structure 71, which is connected to upper support fixed beam 701 and lower support fixed beam 702. The input and output structures can adopt a same-side output arrangement. At this time, a disturbance input electrode 51 is set on the left side, along with an upper driving electrode 61 and a lower driving electrode 62 that cooperate with it. Four fixed output electrodes are set on the right side, defined as upper left induction output electrode 81, lower left induction output electrode 82, upper right induction output electrode 83, and lower right induction output electrode 84. The upper right induction output electrode 83 and the lower right induction output electrode 84 are a single structure and can be considered as the same output electrode; therefore, the upper left induction output electrode 81 and the lower left induction output electrode 82 on the same side can be connected in parallel as one output electrode, and the upper right induction output electrode 83 and the lower right induction output electrode 84 can be connected in parallel as another output electrode, forming a pair of differential output terminals. In this embodiment, each electrode and the resonant beam structure 71 are still capacitively coupled through a comb-tooth structure. The distribution of its movable and fixed parts is as follows... Figure 6 As shown, the motion state is consistent with that of the corresponding structure in the aforementioned embodiments.

[0036] Example 3 like Figure 7 As shown, the difference between this embodiment and Embodiment 2 is that the input structure can be changed to a transverse comb structure; the resonant beam in this embodiment is defined as resonant beam structure 391, which is connected to upper support fixed beam 3920 and lower support fixed beam 3921. At this time, the fixed input electrode is input electrode 3930, the fixed driving electrodes are upper driving electrode 2940 and lower driving electrode 2941, and the fixed output electrodes are inductive output electrode 3931, upper left inductive output electrode 3950, and lower left inductive output electrode 3951. To ensure differential output characteristics, the upper left inductive output electrode 3950 and lower left inductive output electrode 3951 can be connected in parallel as one output terminal, forming a pair of differential output terminals together with inductive output electrode 3931. The driving and output structures in this embodiment partially overlap with those in the aforementioned embodiment, and the structural form and motion state of the overlapping part are the same as in the above embodiment.

[0037] Example 4 This embodiment provides a method for operating a differential micro electric field sensor based on frequency output as described in the above embodiment, including the following steps: An external metal plate is placed in the electric field to be measured, and induced charges are generated on its surface. A fixed input electrode connected to it via a wire generates a proportionally opposite charge. The input capacitance formed between the fixed input comb beam on the fixed input electrode and the adjacent movable input comb beam generates an attractive force under the action of the electrostatic field, causing the movable input comb beam to deflect towards the fixed input comb beam, thereby introducing axial compressive or tensile stress into the resonant beam structure 1, changing its equivalent stiffness and shifting the resonant frequency. An excitation voltage is applied to the fixed driving electrode, causing the resonant beam structure 1 to resonate continuously at a frequency close to its intrinsic frequency. During the resonance process, the extended vertical beams on the left and right sides of the resonant beam structure 1 vibrate in opposite phases, and the output capacitances of the first and second output terminals change in opposite directions. The fixed output electrodes are converted into high-frequency AC voltage signals by a transimpedance amplifier 411, and then differentially amplified by an instrumentation amplifier 412 to obtain an AC differential output voltage. The frequency change corresponding to the AC differential output voltage is detected to measure the strength of the electric field to be measured.

[0038] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A differential miniature electric field sensor based on frequency output, characterized in that: include: A resonant beam structure has at least one pair of symmetrical, vibrating extended vertical beams; the resonant beam structure also includes two parallel thin vertical beams and a transverse beam connecting the two thin vertical beams; the transverse beam is vertically fixed at the middle position of the thin vertical beams; and the left and right ends of the transverse beam extend horizontally away from the thin vertical beams respectively; the extended vertical beam is fixed on the transverse beam and located outside the thin vertical beams; the extended vertical beam is rigidly connected to the transverse beam and can vibrate synchronously with the thin vertical beams; The input structure includes a fixed input electrode connected to a base via a fixed beam and positioned outside the outermost extended vertical beam. An input coupling unit is provided between the fixed input electrode and the adjacent extended vertical beam. An external sensing metal plate is connected to the fixed input electrode and can be placed in the electric field to be measured. The input coupling unit can introduce axial compressive or tensile stress into the resonant beam structure, causing a shift in the resonant frequency. The fixed input electrode and the adjacent extended vertical beam are arranged parallel to each other. The input coupling unit includes a fixed input comb beam positioned on one side of the fixed input electrode and a movable input comb beam positioned on the corresponding extended vertical beam. The fixed input comb beam and the corresponding movable input comb beam are arranged alternately to form an input capacitance comb pair. The driving structure includes a fixed driving electrode and a driving coupling unit. The fixed driving electrode is fixed to the base by a beam. The fixed driving electrode is located on the other side of the extended vertical beam adjacent to the fixed input electrode. A driving coupling unit is provided between the fixed driving electrode and the corresponding extended vertical beam. An excitation voltage can be applied to the fixed driving electrode so that the resonant beam structure can resonate continuously through the driving coupling unit. as well as The output structure includes at least two output units, symmetrically arranged on both sides of the vibration direction under the working mode of the extended vertical beam; each output unit includes a fixed output electrode, the fixed output electrode is fixed to the base through the output beam, and an output coupling unit is provided between the fixed output electrode and the adjacent extended vertical beam; Among them, the output unit located on the same side of the vibration direction under the working mode of the extended vertical beam constitutes the first output end, and the output unit located on the other side of the vibration direction under the working mode of the extended vertical beam constitutes the second output end. The first output end and the second output end constitute a differential output end.

2. The differential miniature electric field sensor based on frequency output according to claim 1, characterized in that: The upper ends of the two thin vertical beams are fixedly connected to horizontally arranged upper support beams, and the lower ends of the two thin vertical beams are fixedly connected to horizontally arranged lower support beams.

3. The differential miniature electric field sensor based on frequency output according to claim 1, characterized in that: The fixed driving electrode is arranged in parallel with the adjacent extended vertical beam. The driving coupling unit includes a fixed driving comb beam disposed on the fixed driving electrode and a movable driving comb beam disposed on the corresponding extended vertical beam. The fixed driving comb beam and the movable driving comb beam are arranged alternately in the horizontal direction to form a driving capacitor comb pair. When an alternating driving voltage is applied, the driving capacitor comb pair generates a periodic electrostatic force to drive the resonant beam structure to resonate and vibrate.

4. The differential miniature electric field sensor based on frequency output according to claim 1, characterized in that: The fixed output electrode is arranged parallel to the adjacent extended vertical beam; the output coupling unit includes a fixed output comb beam disposed on the fixed output electrode and a movable output comb beam disposed on the corresponding extended vertical beam. The fixed output comb beam and the movable output comb beam are arranged alternately to form an output capacitor comb pair, which is used to convert the vibration displacement of the resonant beam structure into changes in output capacitance.

5. The differential miniature electric field sensor based on frequency output according to claim 1, characterized in that: Both the fixed input comb beam and the movable input comb beam are arranged vertically so that adjacent fixed input comb beams and movable input comb beams are arranged in a horizontally staggered manner to form input capacitor comb pairs; or, both the fixed input comb beam and the movable input comb beam are arranged horizontally so that adjacent fixed input comb beams and movable input comb beams are arranged in a vertically staggered manner to form input capacitor comb pairs.

6. The differential miniature electric field sensor based on frequency output according to claim 2, characterized in that: The extended vertical beams are provided in four parts: a first extended vertical beam, a second extended vertical beam, a third extended vertical beam, and a fourth extended vertical beam. The first and second extended vertical beams are provided on the crossbeam located to the left of the thin vertical beam, and the third and fourth extended vertical beams are provided on the crossbeam located to the right of the thin vertical beam. A fixed input electrode is provided on the outer side of the first and fourth extended vertical beams, and a fixed drive electrode is provided on the inner side of the first and fourth extended vertical beams. A fixed output electrode is provided on the inner side of the second and third extended vertical beams.

7. The differential miniature electric field sensor based on frequency output according to claim 2, characterized in that: The extension vertical beam is provided in two parts, including a first extension vertical beam and a second extension vertical beam symmetrically arranged on the left and right sides of the thin vertical beam; a fixed input electrode should be provided on the outer side of the first extension vertical beam, and a fixed drive electrode should be provided on the inner side of the first extension vertical beam; the fixed output electrode should be provided on both the inner and outer sides of the second extension vertical beam.

8. The differential miniature electric field sensor based on frequency output according to claim 2, characterized in that: The extended vertical beams located on the left and right sides of the resonant beam structure vibrate in opposite phases, so that the output capacitance of the first output terminal and the second output terminal changes in opposite directions; the first output terminal and the second output terminal are respectively connected to transimpedance amplifiers, and the transimpedance amplifiers are connected to instrumentation amplifiers.

9. A method for operating the differential micro electric field sensor based on frequency output as described in any one of claims 1 to 8, characterized in that: Includes the following steps: When an external metal plate is placed in the electric field to be measured, an induced charge is generated on its surface; a fixed input electrode connected to it by a wire generates a proportionally opposite charge. The input capacitance formed between the fixed input comb beam on the fixed input electrode and the adjacent movable input comb beam generates an attractive force under the action of the electrostatic field, causing the movable input comb beam to deflect towards the fixed input comb beam, thereby introducing axial compressive or tensile stress into the resonant beam structure, changing its equivalent stiffness, and causing the resonant frequency to shift. An excitation voltage is applied to a fixed driving electrode to make the resonant beam structure resonate continuously at a frequency close to its intrinsic frequency. During the resonance process, the extended vertical beams on the left and right sides of the resonant beam structure vibrate in opposite phases, and the output capacitances of the first and second output terminals change in opposite directions. The fixed output electrodes are converted into high-frequency AC voltage signals by transimpedance amplifiers, and then differentially amplified by instrumentation amplifiers to obtain AC differential output voltages. The frequency change corresponding to the AC differential output voltage is detected to measure the electric field strength under test.

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