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首页> 外文期刊>IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control >The Effects of Phase-Modulated Excitation on the Focused Acoustic Field
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The Effects of Phase-Modulated Excitation on the Focused Acoustic Field

机译：相位调制激励对聚焦声场的影响

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摘要

Various modulation approaches, such as amplitude and frequency modulations, have been applied widely to modify the acoustic field and improve the performance of ultrasound imaging and therapy. However, phase modulation (PM) has not been investigated extensively in the ultrasound applications, especially at a long-pulse duration. In this study, the effects of PM on the acoustic field were investigated. The radiated acoustic pressure waveforms produced using different PM strategies (i.e., sequential phase inversion every cycle, every two cycles, and random phase inversion) were explored, and the distributions of acoustic pressure and average acoustic intensity along and transverse to the transducer axis were compared with those of a sinusoidal wave excitation in both measurement and simulation. It is found that the phase inversion between the modulated signals is not clearly seen in the radiated waveform because of the limited fractional bandwidth of the therapeutic ultrasound transducer. As a result, the radiated waveform has a higher oscillating frequency, and the pressure at the focus and the -6-dB beam size are decreased. Both simulation and measurement show similar trends. Furthermore, produced acoustic fields of the phased array using these PM strategies were also simulated at the varied lateral and axial focus shifting distances. The magnitude and beam size of both the main lobe and grating lobe are found between them, especially at the large focus shifting. In summary, the acoustic field is dependent on the PM, and the appropriate excitation scheme could improve the ultrasound application.
机译：已经广泛应用了各种调制方法，例如幅度和频率调制，以改变声场并提高超声成像和治疗的性能。然而，尚未在超声应用中广泛研究相位调制（PM），尤其是在长脉冲持续时间内。在这项研究中，研究了PM对声场的影响。探讨了使用不同PM策略产生的辐射声压波形（即，顺序相位倒置每个循环，每两个循环和随机相位反转），并进行比较声压和平均声强的分布和横向换能器轴的分布与测量和仿真中的正弦波激发的刺激。结果发现，由于治疗性超声换能器的有限分数带宽，在辐射波形中不清楚地看到调制信号之间的相位反转。结果，辐射波形具有更高的振荡频率，并且焦点处的压力和-6-dB波束尺寸减小。仿真和测量都显示出类似的趋势。此外，还在各种横向和轴向聚焦距离距离处模拟使用这些PM策略的分阶段阵列的产生声场。在它们之间找到主叶和光栅叶的幅度和光束尺寸，尤其是在大焦点移位。总之，声场取决于PM，并且适当的激励方案可以改善超声应用。

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