WO2020253795A1 - 基于模态局部化效应的微弱磁场测量装置及方法 - Google Patents

基于模态局部化效应的微弱磁场测量装置及方法 Download PDF

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WO2020253795A1
WO2020253795A1 PCT/CN2020/096896 CN2020096896W WO2020253795A1 WO 2020253795 A1 WO2020253795 A1 WO 2020253795A1 CN 2020096896 W CN2020096896 W CN 2020096896W WO 2020253795 A1 WO2020253795 A1 WO 2020253795A1
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resonator
magnetic field
resonators
detection electrode
weakly coupled
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PCT/CN2020/096896
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French (fr)
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常洪龙
李文牧
严子木
叶芳
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西北工业大学
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux

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  • the invention relates to a high-precision weak magnetic field measuring device and a corresponding test method under a new theory, and belongs to the field of electronic measuring instruments.
  • the magnetometer is an electronic instrument that can measure the strength and direction of the surrounding magnetic field at the same time.
  • MEMS micromechanical electronic process
  • MEMS magnetometers use permanent magnets, which are combined with electronic tunneling and other technologies to achieve magnetic field strength measurement and obtain good results, with a resolution of up to 300Pt/Hz.
  • permanent magnets due to the hysteresis phenomenon of permanent magnets and the crosstalk error in multi-axis measurement, the stability of such magnetometers is poor, and it is difficult to apply in daily life environments. .
  • another part of MEMS magnetometers based on the Lorentz force measurement principle has the advantages of no crosstalk between axes and easy integrated use, which means that such devices can be easily synchronized.
  • Various types of inertial sensors are integrated and used, while reducing interference such as crosstalk between axes.
  • a type of magnetometer based on amplitude modulation achieves an ultra-high sensitivity of 30nT/Hz and has a good quality factor, but the disadvantage is that its dynamic range is small. In practical applications, it is limited by the measurement range and therefore difficult to apply to various scenarios.
  • another type of magnetometer based on frequency modulation has a better dynamic range, but there is a problem of frequency drift during the measurement process, which will greatly affect the sensitivity and resolution of this type of device, and it is difficult to achieve high Accuracy.
  • the present invention proposes a series magnetometer with multiple weakly coupled resonators.
  • a grid structure is designed to induce Lorentz force to be sensitive to the magnetic field to be measured, which greatly improves the detection.
  • this invention can realize high-precision measurement of weak magnetic fields, and has a larger dynamic range and better noise suppression capabilities.
  • the present invention proposes a high-precision weak magnetic field measurement device, which is based on the modal localization effect of a multi-degree-of-freedom weakly coupled resonator and can realize the measurement of a micro-Tesla-level weak magnetic field.
  • a high-precision weak magnetic field measurement device mainly includes a weakly coupled resonator, a grid structure and an electrode circuit part;
  • the weakly coupled resonator includes no less than two identical resonators, resonator one 301, resonator two 303, and a resonator array 302 located in the middle.
  • the rigidity of the resonators in the resonator array 302 is completely The same, the number can be zero; there is a grating structure 312 at a certain gap outside the resonator 301; the stiffness of the resonator 301 and the resonator 303 are exactly the same, and the resonator array 302 is placed sequentially in the horizontal direction; each resonance
  • the resonators are all connected to the horizontal mechanical coupling beam 304 through the vertical resonance beams on both sides, that is, the resonator one 301, the resonator array 302, and the resonator two 303 are connected in series in the horizontal direction through the mechanical coupling beam 304; Both ends of the coupling beam 304 are fixed to the anchor points 305 by vertical short beams.
  • the mechanical coupling beam 304 and the short beams on both sides are collectively referred to as a "bridge-type coupling beam".
  • the stiffness of the bridge-type coupling beam is much smaller than that of the resonance beam. Further, the ratio of the stiffness of the bridge-type coupling beam to the stiffness of the resonance beam is not higher than 1:1000, so as to realize a weak coupling connection between the resonators;
  • the first detection electrode 306 and the second detection electrode 307 form a resonator one 301 differential detection electrode to detect the amplitude of the resonator one 301; the third detection electrode 308 and the fourth detection electrode 309 form a resonator two 303 differential detection electrode, Detect the amplitude of resonator two 303; AC drive 310 and anchor point 305 apply an alternating current to the entire weakly coupled resonator, and Lorentz force is generated in the magnetic field to drive the simple resonance of the resonator; adjustment electrode 311 passes through resonator two 303 realizes the adjustment of the initial vibration state of the entire weakly coupled resonator; the grating structure 312 induces the applied magnetic field and perturbs the stiffness of the resonator one 301 to change the vibration state of the resonator one 301; due to the resonator one 301 and the resonator two 303, and the resonator array 302 in the middle have a weak coupling relationship, and the vibration state of the
  • Step 1 Apply alternating current on resonator one 301, resonator two 303, and resonator array 302, and apply direct current on grid structure 312;
  • Step 2 Place the current-applied chip into a set of arbitrary multiple known magnetic fields to obtain multiple corresponding amplitude differences u i u 0 .
  • Step 3 Obtain the fitting curve corresponding to the input magnetic field with different amplitude differences through the linear fitting method.
  • Step 4 Place the chip in the magnetic field to be measured to obtain an amplitude difference u 0 , and substitute this amplitude difference u 0 into the fitting curve to obtain the corresponding magnetic field strength, which is the magnetic field strength of the magnetic field to be measured.
  • the beneficial effect of the present invention is to provide a high-precision magnetometer based on the modal localization effect.
  • a plurality of resonators are weakly coupled in series through a bridge-type coupling beam.
  • the design of the bridge-type coupling beam can release the axial stress generated during the processing, and ensure that the device is not affected by the residual stress; two outer sides
  • the output signal of the resonator is detected by two sets of detection electrodes and extracted for difference.
  • This detection method can not only enhance the signal strength, but more importantly, it can eliminate the feedthrough capacitance caused by the potential difference between the driving electrode and the detection electrode. Signal interference can greatly improve the stability and accuracy of the measurement signal.
  • an alternating current is applied to the entire weakly coupled resonator, and the magnetic field force is used to drive the resonator to vibrate, while achieving the effect of inducing changes in the magnetic field.
  • the externally designed grid structure can be used to generate a direct current to sense the magnetic field to be measured. By fully expanding the grid structure density, the directional current is greatly increased. Therefore, the measurement sensitivity is greatly improved on the basis of the weak magnetic field detected by the resonator.
  • the directional current on the grid structure is moved by the Lorentz force, which changes the electrostatic negative stiffness between the resonator and the resonator, thereby affecting
  • the energy distribution of the weakly coupled resonator system causes drastic changes in the mode of the resonator.
  • Using the amplitude difference of the output resonator as the output dimension can amplify the sensitivity of the magnetic field measurement chip, ensuring ultra-high precision magnetic field measurement.
  • taking the amplitude difference as the output dimension has outstanding restraint power to environmental noise, and adapts to the Joule heating problem that is easily generated by the excitation current in the magnetic field detection.
  • Figure 1 is an equivalent schematic diagram of a weakly coupled resonator array based on modal localization effects.
  • Fig. 2 is a working schematic diagram of a high-precision magnetometer with modal localization effect of the present invention.
  • Figure 3 is a schematic diagram of the structure of a high-precision magnetometer based on modal localization effects.
  • Figure 4 is a schematic diagram of the detection method implementing the present invention (taking three degrees of freedom as an example).
  • Fig. 5 is a fitting curve of amplitude difference ratio versus magnetic field size obtained by implementing the present invention (taking three degrees of freedom as an example).
  • 201-High-precision magnetometer chip of the present invention 202-Grate structure model, 203-Multi-degree-of-freedom weakly coupled resonator (indicated by three degrees of freedom in the figure), 204-Resonator output signal, 205-Detection circuit.
  • This embodiment uses a three-degree-of-freedom weakly coupled resonator to implement self-driving in a magnetic field.
  • a grid structure is used to greatly change the energy distribution of the resonator array, and combined with a detection circuit, the magnitude of the magnetic field is detected by the amplitude difference between the first and the last two resonators.
  • the high-precision weak magnetic field measurement device in this embodiment mainly includes a weakly coupled resonator, a grid structure 312 and an electrode part; the weakly coupled resonator includes three identical resonators, resonator one 301 and resonator two 303 , And the middle resonator.
  • the first resonator 301 has a grating structure 312 at 3 ⁇ m outside; the stiffness of the first resonator 301 and the second 303 are exactly the same, and the middle resonator is placed in sequence in the horizontal direction; each resonator is The vertical resonance beams on both sides are connected to the horizontal mechanical coupling beam 304, that is, resonator one 301, intermediate resonator, and resonator two 303 are connected in series in the horizontal direction through mechanical coupling beam 304; mechanical coupling beam 304 Both ends are fixed to the anchor points 305 by vertical short beams. Therefore, the mechanical coupling beam 304 and the short beams on both sides are collectively referred to as a "bridge coupling beam".
  • the ratio of the stiffness of the bridge coupling beam to the stiffness of the resonance beam is 1:1200 , So as to realize the weak coupling connection between the resonators;
  • the first detection electrode 306 and the second detection electrode 307 form a resonator one 301 differential detection electrode to detect the amplitude of the resonator one 301; the third detection electrode 308 and the fourth detection electrode 309 form a resonator two 303 differential detection electrode, Detect the amplitude of resonator two 303; AC drive 310 and anchor point 305 apply an alternating current to the entire weakly coupled resonator, and Lorentz force is generated in the magnetic field to drive the simple resonance of the resonator; adjustment electrode 311 passes through resonator two 303 realizes the adjustment of the initial vibration state of the entire weakly coupled resonator; the grating structure 312 induces the applied magnetic field and perturbs the stiffness of the resonator one 301 to change the vibration state of the resonator one 301; due to the resonator one 301 and the resonator two There is a weak coupling relationship between 303 and the intermediate resonator, and the vibration state of the entire weakly coupled
  • the detailed working process of the high-precision weak magnetic field measuring device in this embodiment is as follows: an alternating voltage is applied between the driving electrode 310 and the anchor point 305, so that the first resonator 301, the intermediate resonator, and the second resonator 303 pass the alternating current; DC current is applied to the type structure 312. Place the magnetic field measurement chip in the magnetic field to be measured, adjust the alternating voltage applied on the driving electrode 310, and the changing Lorentz force makes the resonator vibrate near the resonance frequency;
  • x 1 and x 2 are the vibration displacements of the two resonators
  • ⁇ 0 is the resonant frequency point of the resonator
  • Q is the quality factor
  • t is the time
  • ⁇ is the coupling coefficient-the stiffness of the coupling beam 304 and the resonator 301
  • m is the mass of resonator one 301 and resonator two 303
  • F 1 and F 2 are the driving forces received by resonator one 301 and resonator two 303, respectively.
  • B is the size of the external magnetic field
  • i is the alternating current
  • l eff1 and l eff2 are the effective lengths of resonator one 301 and resonator two 303 respectively.
  • the grid structure 312 receives the Lorentz force in the horizontal direction and produces a displacement in the horizontal direction, which causes a stiffness disturbance to the resonator 301.
  • the disturbance magnitude ⁇ is:
  • A represents the effective facing area of the grid structure 312 and the weakly coupled resonator
  • G 0 represents the distance between the grid structure 312 and the weakly coupled resonator
  • V represents the distance between the grid structure 312 and the weakly coupled resonator
  • I represents the magnitude of the directional current on the grid structure 312
  • L represents the total length of all longitudinal beam structures in the grid structure 312
  • k grili represents the stiffness of the grid structure 312
  • ⁇ represents the vacuum dielectric constant.
  • Transimpedance amplifiers 405, 406, 407, and 408 are connected to the resonator detection electrodes, and differential amplifiers 409 and 410 are used to obtain differential amplified amplitude signals of resonators one 301 and two 303, and the resonator output signal amplitude difference is obtained through subtractor 411. .
  • the stiffness of resonator one 301, intermediate resonator, and resonator two 303 have been determined, the total length L of the longitudinal beam structure of the grid structure 312 has been determined, and the stiffness of the grid structure 312 has been determined.
  • Grili has determined that the AC current i is known, and the detected amplitude difference U has a one-to-one correspondence with the magnetic field strength B.
  • Step 1 Apply an alternating current to the first resonator 301, the intermediate resonator, and the second resonator 303, and apply a direct current to the grid structure 312.
  • Step 2 Perform calibration, place the chip applying current into a set of ten known magnetic fields, the size of the magnetic field B i is arranged in an arithmetic within 0-50mT; 10 different amplitude differences u i are obtained from the subtractor 411.
  • Step 3 Record ten sets of amplitude differences u i and the corresponding magnetic field size B i , and obtain calibration curves of different amplitude differences corresponding to the input magnetic field through a linear fitting method, as shown in FIG. 5.
  • Step 4 Place the chip in the magnetic field to be measured of unknown size, obtain an amplitude difference u 0 from the subtractor 411, and obtain the magnetic field strength B 0 according to the calibration curve, which is the magnetic field strength of the magnetic field to be measured.

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  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Magnetic Variables (AREA)

Abstract

本发明公开了一种高灵敏度磁场测量方法及装置，属于电子测量仪器领域。包括磁场测量芯片及测试信号的处理方法。芯片包括不少于两个的弱耦合谐振器、驱动电极、检测电极和外侧的栅型结构。通过驱动电极在弱耦合谐振器中施加交变电流，芯片置入垂直磁场时，谐振器受到变化的洛伦兹力产生简谐振动；外界磁场变化时，谐振器的振动状态随之变化。同时，在栅型结构上施加直流电流，其受到水平方向洛伦兹力，改变其与弱耦合谐振器之间的静电负刚度，使得弱耦合谐振器系统的能量分布出现剧烈失衡。输出谐振器两侧设计两组检测电极，实现单谐振器振幅差分检测，消除馈通电容干扰，通过测量谐振器振幅差可以实现微弱磁场强度的高灵敏度测量；本发明可实现微弱磁场的实时测量并具有较强的抗干扰能力，具有较高的使用意义。

Description

基于模态局部化效应的微弱磁场测量装置及方法
所属领域：
本发明涉及了一种新理论下的高精度微弱磁场测量装置及相应的测试方法，属于电子测量仪器领域。
背景技术
从古代的司南开始，人类对于磁场强度的探测与应用已有数千年的历史。近现代以来，磁场强度探测在诸多科学研究和工程技术领域，尤其是在航空航天导航系统领域具有重要的应用需求。磁强计是一种能够同时测量周边磁场强度与方向的电子仪器，而微机械电子工艺(MEMS)下的磁强计由于其低成本，低功耗以及便于集成化的诸多优点，成为了目前磁强计研究的一大热点。
从原理上看，一部分MEMS磁强计采用了永磁体，通过结合电子隧穿等技术实现磁场强度测量并且获得了不错的结果，分辨率可达300Pt/Hz。然而对于基于永磁体的磁强计来说，由于永磁体存在磁滞现象，并且在多轴测量上存在轴间串扰误差，导致此类磁强计的稳定性较差，难以应用在日常生活环境。相比于基于永磁体的MEMS磁强计，另一部分基于洛伦兹力测量原理的MEMS磁强计具有轴间无串扰、便于集成化使用的优势，这意味着此类器件被可以方便地同各类惯性传感器集成使用，同时降低了轴间串扰等干扰。
基于洛伦兹力的MEMS磁强计中，一类基于幅度调制的磁强计实现了30nT/Hz的超高灵敏度，并且具有良好的品质因数，但是不足之处在于其动态范围较小，在实际应用中受限于测量范围因此难以应用于各类场景。相比于前者，另一类基于频率调制的磁强计拥有更好的动态范围，然而在测量过程中其存在频率漂移问题，这将大大影响此类器件的灵敏度与分辨率，难以做到高精度。
近年来，一种崭新的模态局部化机理被用于提升传感器的灵敏度，其核心在于通过幅值差调制来反映敏感量的变化，而非幅值或频率。基于幅值差调制的优势在于具备极高的测量精度的同时，能够有效抑制环境噪声对测量的影响。受此机理启发，本发明提出一种多个弱耦合谐振器串联式磁强计，同时基于模态局部化效应设计了一种栅型结构感应洛伦兹力从而敏感待测磁场，大幅提升检测灵敏度，使用幅值差调制作为输出量纲以提高测量精度，同时也兼具了所需求的工作稳定性。与上述其他磁强计相比，该发明可实现对微弱磁场的高精度测量，并具有较大的动态范围和较好的噪声抑制能力。
发明内容：
本发明提出了一种高精度微弱磁场测量装置，它基于多自由度弱耦合谐振器的模态局部化效应，能够实现微特斯拉级别微弱磁场的测量。
一种高精度微弱磁场测量装置主要包括弱耦合谐振器、栅型结构及电极电路部分；
所述弱耦合谐振器包含了不低于两个的完全相同的谐振器，谐振器一301、谐振器二303，以及位于中间的谐振器阵列302，其中谐振器阵列302中的谐振器刚度完全相同，数量可为零；所述谐振器一301外侧一定间隙处有栅型结构312；谐振器一301与谐振器303刚度完全相同，与谐振器阵列302在水平方向上顺序放置；每个谐振器均通过两侧垂直方向上的谐振梁与水平方向的机械耦合梁304相连接，即谐振器一301、谐振器阵列302、谐振器二303通过机械耦合梁304实现水平方向上串联连接；机械耦合梁304两端通过垂直方向短梁固定于锚点305上，故将所述机械耦合梁304与两侧短梁合称为“桥式耦合梁”，桥式耦合梁刚度远小于谐振梁刚度，进一步的，所述桥式耦合梁刚度与谐振梁刚度比值不高于1：1000，从而实现谐振器间弱耦合连接；
也可以有另一栅型结构312同时以一定间隙置于谐振器二303外侧；
第一检测电极306与第二检测电极307形成谐振器一301差分检测电极，对谐振器一301的振幅进行检测；第三检测电极308与第四检测电极309形成谐振器二303差分检测电极，对谐振器二303的振幅进行检测；交流驱动310和锚点305给整个弱耦合谐振器上施加交变电流，磁场中产生洛伦兹力驱动谐振器简谐振动；调节电极311通过谐振器二303实现对整个弱耦合谐振器初始振动状态的调节；栅型结构312感应施加的磁场并对谐振器一301进行刚度扰动，改变谐振器一301的振动状态；由于谐振器一301、谐振器二303，以及位于中间的谐振器阵列302之间存在弱耦合关系，整个弱耦合谐振器的振动状态也相应改变；由谐振器一301差分检测电极与谐振器二303差分检测电极输出的信号经信号处理电路205得到所述磁强计最终的输出信号。
本发明提出的一种高精度磁场强度测量方法，包括如下步骤：
步骤一：在谐振器一301、谐振器二303，谐振器阵列302上施加交变电流，在栅型结构312上施加直流电流；
步骤二：将施加电流的芯片置入一组任意多个已知磁场中，得到对应的多个振幅差u iu 0。
步骤三：通过线性拟合的方法得到不同振幅差对应输入磁场的拟合曲线。
步骤四：将芯片置入待测磁场当中，得到一个振幅差u 0，将此振幅差u 0代入拟 合曲线中，得到对应的磁场强度，即为待测磁场的磁场强度。
本发明的有益效果：提供一种基于模态局部化效应的高精度磁强计。本发明中通过桥式耦合梁对多个谐振器进行串联弱耦合，该桥型耦合梁的设计可以释放由于加工过程中产生的轴向应力，保证了器件不受残余应力的影响；两个外侧谐振器的输出信号均由两组检测电极检测并引出进行差分，这种检测方法不仅可以增强信号的强度，更重要的是可以消除由驱动电极与检测电极之间存在的电势差引起的馈通电容信号干扰，可以大幅提升测量信号的稳定性与准确度。
特别的，针对微弱磁场检测的特殊应用，给整个弱耦合谐振器施加交变电流，利用磁场力驱动谐振器振动，同时达到感应磁场变化的效果。外侧设计的栅型结构可用于产生直流电流从而敏感待测磁场，通过充分拓展栅型结构密度极大地增加了定向电流，因此在谐振器检测微弱磁场的基础上，大幅提升测量灵敏度。当施加待测磁场至器件正上方时，基于弗莱明左手定则，栅型结构上的定向电流受洛伦兹力作用而运动，改变了与谐振器之间的静电负刚度，从而影响了弱耦合谐振器系统的能量分布，导致谐振器模态的剧烈变化，以输出谐振器的振幅差作为输出量纲可放大磁场测量芯片的灵敏度，保证了超高精度的磁场测量。同时，以幅值差作为输出量纲对环境噪声有突出的抑制力，适应磁场检测中因激励电流易产生的焦耳热问题。
附图说明：
图1是基于模态局部化效应的弱耦合谐振器阵列的等效示意图。
图2是本发明模态局部化效应的高精度磁场计的工作示意图。
图3是基于模态局部化效应的高精度磁场计的结构示意图。
图4是实施本发明的检测方法示意图(以三自由度为例)。
图5是实施本发明得到的振幅差比对磁场大小的拟合曲线(以三自由度为例)。
图中：
101-谐振器一等效质量模型，102-谐振器阵列等效质量模型，103-谐振器二等效质量模型，104-谐振器一等效刚度模型，105-连接谐振器一等效质量模型与谐振器阵列等效质量模型的耦合梁模型，106-连接谐振器阵列等效质量模型与谐振器二等效质量模型的耦合梁模型，107-谐振器二的等效刚度模型。
201-本发明高精度磁强计芯片，202-栅型结构模型，203-多自由度弱耦合谐振器(图中以三自由度示意)，204-谐振器输出信号，205-检测电路。
301-谐振器一,302-谐振器阵列,303-谐振器二,304-桥式耦合梁，305-锚点，306-第一检测电极，307-第二检测电极，308-第三检测电极，309-第四检测电极，310-驱动电极，311-调节，312-栅型结构。
401-第一检测电极输出，402-第二检测电极输出，403-第三检测电极输出,404-第四检测电极输出,405-第一跨阻放大器，406-第二跨阻放大器，407-第三跨阻放大器,408-第四跨阻放大器，409-谐振器一信号差分放大器，410-谐振器二信号差分放大器,411-减法器。
具体实施方式：
本实施例使用三自由度弱耦合谐振器实施，在磁场中实现自驱动，同时使用格栅结构大幅改变谐振器阵列能量分布，结合检测电路，以首尾两个谐振器振幅差检测磁场大小。
本实施例中的高精度微弱磁场测量装置主要包括弱耦合谐振器、栅型结构312及电极部分；所述弱耦合谐振器包含三个完全相同的谐振器，谐振器一301、谐振器二303，以及中间谐振器，所述谐振器一301外侧3μm处有栅型结构312；谐振器一301与谐振器二303刚度完全相同，与中间谐振器在水平方向上顺序放置；每个谐振器均通过两侧垂直方向上的谐振梁与水平方向的机械耦合梁304相连接，即谐振器一301、中间谐振器、谐振器二303通过机械耦合梁304实现水平方向上串联连接；机械耦合梁304两端通过垂直方向短梁固定于锚点305上，故将所述机械耦合梁304与两侧短梁合称为“桥式耦合梁”，桥式耦合梁刚度与谐振梁刚度比值1：1200，从而实现谐振器间弱耦合连接；
第一检测电极306与第二检测电极307形成谐振器一301差分检测电极，对谐振器一301的振幅进行检测；第三检测电极308与第四检测电极309形成谐振器二303差分检测电极，对谐振器二303的振幅进行检测；交流驱动310和锚点305给整个弱耦合谐振器上施加交变电流，磁场中产生洛伦兹力驱动谐振器简谐振动；调节电极311通过谐振器二303实现对整个弱耦合谐振器初始振动状态的调节；栅型结构312感应施加的磁场并对谐振器一301进行刚度扰动，改变谐振器一301的振动状态；由于谐振器一301、谐振器二303，以及中间谐振器之间存在弱耦合关系，整个弱耦合谐振器的振动状态也相应改变；由谐振器一301差分检测电极与谐振器二303差分检测电极输出的信号经信号处理电路205得到所述磁强计最终的输出信号。
本实施例中高精度微弱磁场测量装置详细工作过程如下：在驱动电极310与锚点305之间施加交变电压，使得谐振器一301、中间谐振器、谐振器二303通过交变电流；在栅型结 构312中施加直流电流。将磁场测量芯片放置在待测磁场中，调节驱动电极310上施加的交变电压，变化的洛伦兹力使得谐振器在谐振频率附近振动；
谐振器一301、谐振器二303受磁场力驱动时的动力学方程为：
Figure PCTCN2020096896-appb-000001
其中，x 1、x 2为两个谐振器的振动位移，ω 0为谐振器谐振频率点，Q为品质因数，t为时间，κ为耦合系数——耦合梁304与谐振器一301刚度的差值，m为谐振器一301、谐振器二303的质量，F 1、F 2分别为谐振器一301、谐振器二303受到的驱动力。
F 1＝Bil eff1＝F 2＝Bil eff2＝F
其中B为外界磁场大小，i为交变电流，l eff1、l eff2分别为谐振器一301、谐振器二303的有效长度。栅型结构312受到水平方向洛伦兹力，产生水平方向位移，对谐振器一301产生刚度扰动，扰动大小δ为：
Figure PCTCN2020096896-appb-000002
其中，其中A表示栅型结构312与弱耦合谐振器有效正对面积；G 0表示栅型结构312与弱耦合谐振器之间的间距；V表示栅型结构312与弱耦合谐振器之间的电势差；I表示栅型结构312上定向电流的大小；L表示栅型结构312中所有纵向梁结构的总长度；k grili表示栅型结构312的刚度，ε表示真空介电常数。
两个谐振器振幅差公式为
u i＝x i1-x i2
有
Figure PCTCN2020096896-appb-000003
跨阻放大器405、406、407、408与谐振器检测电极相连，通过差分放大器409、410得到谐振器一301、二303的差分放大振幅信号，通过减法器411处得到谐振器输出信号幅值差。每个谐振器具有两个谐振峰值，代表弱耦合谐振器的两个主要模态，谐振器一：X 11与X 12；谐振器二：X 21与X 22。选择每个谐振器的第一个谐振峰值计算振幅差U＝X 11-X 21。
综上所述，芯片加工完成后，由于谐振器一301、中间谐振器、谐振器二303的刚度大小已确定，栅型结构312纵向梁结构的总长度L已确定，栅型结构312刚度k grili已确定，交流电流i大小已知，检测到的振幅差U与磁场强度大小B存在一一对应的关系。
本实施例中的一种高灵敏度磁场测量方法，包括如下步骤：
步骤一：在谐振器一301、中间谐振器、谐振器二303上施加交变电流，在栅型结构312上施加直流电流。
步骤二：进行标定，将施加电流的芯片置入一组十个已知磁场中，磁场大小B i在0-50mT内呈等差排列；从减法器411得到10个不同的振幅差u i。
步骤三：记录十组振幅差u i以及对应的磁场大小B i，通过线性拟合的方法得到不同振幅差对应输入磁场的标定曲线，曲线图如附图5所示。
步骤四：将芯片置入未知大小的待测磁场中，从减法器411得到一个振幅差u 0，根据标定曲线得磁场强度B 0，即为待测磁场的磁场强度大小。

Claims (4)

  1. 一种高精度微弱磁场测量装置，其特征在于，主要包括弱耦合谐振器、栅型结构及电极电路部分；
    所述弱耦合谐振器包含了不低于两个的完全相同的谐振器，谐振器一301、谐振器二303，以及位于中间的谐振器阵列302，其中谐振器阵列302中的谐振器刚度完全相同，数量可为零；所述谐振器一301外侧一定间隙处有栅型结构312；谐振器一301与谐振器303刚度完全相同，与谐振器阵列302在水平方向上顺序放置；每个谐振器均通过两侧垂直方向上的谐振梁与水平方向的机械耦合梁304相连接，即谐振器一301、谐振器阵列302、谐振器二303通过机械耦合梁304实现水平方向上串联连接；机械耦合梁304两端通过垂直方向短梁固定于锚点305上，故将所述机械耦合梁304与两侧短梁合称为“桥式耦合梁”，桥式耦合梁刚度远小于谐振梁刚度，从而实现谐振器间弱耦合连接；
    第一检测电极306与第二检测电极307形成谐振器一301差分检测电极，对谐振器一301的振幅进行检测；第三检测电极308与第四检测电极309形成谐振器二303差分检测电极，对谐振器二303的振幅进行检测；交流驱动310和锚点305给整个弱耦合谐振器上施加交变电流，磁场中产生洛伦兹力驱动谐振器简谐振动；调节电极311通过谐振器二303实现对整个弱耦合谐振器初始振动状态的调节；栅型结构312感应施加的磁场并对谐振器一301进行刚度扰动，改变谐振器一301的振动状态；由于谐振器一301、谐振器二303，以及位于中间的谐振器阵列302之间存在弱耦合关系，整个弱耦合谐振器的振动状态也相应改变；由谐振器一301差分检测电极与谐振器二303差分检测电极输出的信号经信号处理电路205得到所述磁强计最终的输出信号。
  2. 一种如权利要求1所述高精度微弱磁场测量装置，其特征在于，所述桥式耦合梁刚度与谐振梁刚度比值不高于1：1000。
  3. 一种如权利要求1所述高精度微弱磁场测量装置，其特征在于，所述栅型结构312同时以一定间隙置于谐振器二303外侧。
  4. 使用如权利要求1、2或3之一所述装置进行高精度磁场强度测量的方法，其特征在于，包括如下步骤：
    步骤一：在谐振器一301、谐振器二303，谐振器阵列302上施加交变电流，在栅型结构312上施加直流电流；
    步骤二：将施加电流的芯片置入一组任意多个已知磁场中，得到对应的多个振幅差u iu 0。
    步骤三：通过线性拟合的方法得到不同振幅差对应输入磁场的拟合曲线。
    步骤四：将芯片置入待测磁场当中，得到一个振幅差u 0，将此振幅差u 0代入拟合曲线中，得到对应的磁场强度，即为待测磁场的磁场强度。
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