基于磁致伸缩效应的声表面波电流传感器研究

Study on SAW Current Sensor Based on Magnetostrictive Effect

该文设计制作了一种基于磁致伸缩效应的声表面波(SAW)电流传感器,采用了磁致伸缩铁钴合金(FeCo)薄膜,并对其性能进行实验研究。传感器采用双通道300 MHz声表面波延迟线型振荡器结构,以128°YXLiNbO_3为压电基片,在其表面覆盖与其温度系数极性相反的SiO_2薄膜来改善器件温度稳定性,并在声传播路径上溅射FeCo薄膜用以感知电流量。在电流产生磁场作用下,FeCo薄膜发生磁致伸缩应变,导致声传播速度的变化,进而以振荡器频率信号的改变来表征待测电流。该文通过对不同FeCo膜厚及不同FeCo薄膜长宽比的传感器进行实验分析,以获得优化的传感功能结构。实验结果表明,在优化的FeCo薄膜厚度(500nm)和长宽比(2∶1)条件下,所研制的声表面波电流传感器的灵敏度为12.375kHz/A。

In this paper,a kind of surface acoustic wave（SAW）current sensor based on the magnetostrictive effect was designed,the sensor adopted magnetostrictive FeCo thin film and its characteristics were studied experimentally The SAW current sensor used 300 MHz dual-channel delay line oscillator,and 128°YX-LiNbO_3 as piezoelectric substrate.SiO_2 thin film layer was coated on the piezoelectric substrate to improve the temperature stability because they had opposite temperature coefficient polarity,and the magnetostrictive FeCo film was sputtered on one of the SAW delay lines to percept the current.Under the magnetic field of desired current,the FeCo film produces magnetostrictive strain,and results in SAW phase velocity changes,and then the current to be measured is characterized by the change of the frequency signal of SAW oscillator.SAW current sensors with different thickness and different aspect ratio of FeCo film were tested in the experiments to obtain optimized sensing structure.The experimental results show that the sensitivity of the developed SAW current sensor is up to 12.375 kHz/A with optimized FeCo film thickness of 500 nm and aspect ratio of 2∶1.