静电推挽驱动-电磁感应检测谐振式微型磁传感器

For non-contact current sensing purpose, the magnetic sensor should have good linearity, good sensitivity, large magnetic field measurement range and large bandwidth. Thus, this project proposes a resonant magnetic field microsensor with electrostatic push-pull driving and electromagnetic induction sensing. The proposed microsensor is driven to square extensional mode by push-pull electrostatic driving, and exploits the principle of electromagnetic induction to detect external magnetic field through the generated electromotive force in the planar induction coil, which is placed on top of the resonant plate. This project combines the principle of electromagnetic induction with the vibrating theory to build a model for the proposed push-pull magnetic sensor. The proposed sensor will be fabricated by Cavity-SOI approach and the movable structures are released by dry etching process. Moreover, the floating sensing structure will be sealed and protected by wafer bonding. A phase-locked loop will be used to detect the high frequency weak electromagnetic induction voltage signals from the induction coil. Because the magnetic sensor in this project employs electromagnetic induction sensing approach to detect the external magnetic field and the induced electromotive force is proportional to the magnetic flux density, the output of the proposed sensor should have a good linearity. Furthermore, the proposed sensor is free from hysteresis and magnetic saturation, which implies a large magnetic field measurement range and large response bandwidth. Due to that the electrostatic push-pull driving doubles driving force, the sensitivity can be improved, and the power dissipation can also be reduced. Additionally, the proposed sensor has low temperature coefficient, since both the electrostatic driving and electromagnetic induction sensing approach are insensitive to temperature. Therefore, the proposed device can operate well in a wide temperature range.

针对非接触电流传感对磁传感器高线性、高灵敏度、大响应范围、高带宽的要求，本项目提出了一种静电推挽驱动-电磁感应检测谐振式微型磁传感器，利用谐振振子上金属线圈切割磁感线实现磁场强度和方向的测量。本项目拟将电磁感应定律与振动理论相结合，建立推挽结构电磁感应磁传感器的器件模型；采用Cavity-SOI工艺，利用干法刻蚀释放可动感应微结构，并通过圆片级键合实现微结构的密封保护；通过锁相放大技术，实现对高频微弱电磁感应电压信号的精确检测。本项目提出的磁传感器基于电磁感应原理进行传感，感应电动势与磁场强度成正比，输出信号具有很好的线性，并且避免了磁滞和磁饱和，提高了磁场测量范围和响应带宽；采用静电推挽驱动将驱动力提高1倍，提高了器件灵敏度，降低了器件功耗。此外，由于静电驱动和电磁感应两种机制对温度都不敏感，本项目提出的磁传感器也将具有较小的温度系数，可在较大温度范围工作。

本课题以微机械谐振器为基础，结合电磁感应定律实现了一种静电驱动-电磁感应敏感的三轴谐振式MEMS磁场传感器，适用于位置感知，惯性导航，智能交通，材料非破坏性测试等领域。.建立了磁场传感器的理论模型，在理论模型的指导下通过对比论证设计了两种敏感结构分别工作在收缩扩张模态和扭转模态用来测量面外和面内磁场；对于工作在扭转模态的敏感结构创新性的采用垂直交错的梳齿电极取代常规的平板电极以降低空气阻尼并且避免了吸合现象；基于两种敏感结构，提出了集成式三轴磁场传感器的实现方案。.开发了磁场传感器制作方法。提出并采用一种简单的自对准工艺实现了垂直交错梳齿电极的制作，降低了工艺成本和复杂度。.研究了微机械谐振器中存在的馈通效应。采用导纳圆图形象的解释了馈通效应对器件谐振特性测试的影响，讨论了根据测试曲线获得谐振频率和Q值的参数提取法，并在器件设计，版图布局和PCB设计三个方面给出了降低馈通效应的方法，从而为谐振式MEMS传感器的设计优化，接口电路设计以及器件性能测试提供指导。.设计了完整的传感器接口电路，包括闭环自激驱动和信号锁相放大。加入温度补偿二极管消除温度漂移造成的检波误差，将器件的TCS降低至-265 ppm/℃。.基于搭建的磁场传感器测试平台对器件性能进行了详细测试。测试表明，器件具有准零功耗，低至0.06%的非线性误差，不低于37 dB的交叉轴抑制比，-20 ~ 80 ℃测试温区内低至-265 ppm/℃的TCS和384 ppm/℃的TCO以及不低于98dB的动态范围。目前大气下面外和面内磁场的分辨率分别为3 μT和6 μT。

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