School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China.
Sensors (Basel). 2023 Apr 13;23(8):3943. doi: 10.3390/s23083943.
The main disadvantage of the electromagnetic acoustic transducer (EMAT) is low energy-conversion efficiency and low signal-to-noise ratio (SNR). This problem can be improved by pulse compression technology in the time domain. In this paper, a new coil structure with unequal spacing was proposed for a Rayleigh wave EMAT (RW-EMAT) to replace the conventional meander line coil with equal spacing, which allows the signal to be compressed in the spatial domain. Linear and nonlinear wavelength modulations were analyzed to design the unequal spacing coil. Based on this, the performance of the new coil structure was analyzed by the autocorrelation function. Finite element simulation and experiments proved the feasibility of the spatial pulse compression coil. The experimental results show that the received signal amplitude is increased by 2.3~2.6 times, the signal with a width of 20 μs could be compressed into a δ-like pulse of less than 0.25 μs and the SNR is increased by 7.1-10.1 dB. These indicate that the proposed new RW-EMAT can effectively enhance the strength, time resolution and SNR of the received signal.
电磁声换能器（EMAT）的主要缺点是能量转换效率低和信噪比（SNR）低。这个问题可以通过时域中的脉冲压缩技术来改善。在本文中，提出了一种新的不等间距线圈结构，用于瑞利波 EMAT（RW-EMAT），以替代具有等间距的常规曲折线线圈，从而允许在空间域中对信号进行压缩。分析了线性和非线性波长调制，以设计不等间距线圈。在此基础上，通过自相关函数对新线圈结构的性能进行了分析。有限元模拟和实验证明了空间脉冲压缩线圈的可行性。实验结果表明，接收信号的幅度增加了 2.3~2.6 倍，宽度为 20 μs 的信号可以被压缩成小于 0.25 μs 的 δ 脉冲，SNR 提高了 7.1-10.1 dB。这表明所提出的新 RW-EMAT 可以有效地增强接收信号的强度、时间分辨率和 SNR。
