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压电圆柱对平面声波的散射——换能器的传递函数、瞬态响应及其相位重现

SCATTERING OF PLANE WAVE BY PIEZOELECTRIC CYLINDER——TRANSFER FUNCTION, TRANSIENT RESPONSES AND PHASE RECONSTRUCTION OF TRANSDUCER

  • 摘要: 在克希霍夫假定下,本文提出了径向极化压电圆柱的薄壳理论。作为理论的一个应用,我们利用格林函数和分离变量法求解了压电圆柱对平面声波的散射问题,得到了圆柱表面振速分布和总声场的简正波级数表达式。由此给出了压电圆柱作为声接收器的传递函数的解析表达式,利用FFT便可算出其瞬态响应。对于PZT-5压电陶瓷圆柱,计算了它的传递函数、脉冲响应和阶跃响应。
    计算结果表明,脉冲响应呈现出典型的最小相位行为,因此压电圆柱接收器属于最小相位系统,从而它的传递函数的相位谱可以利用希尔伯特变换从它的振幅谱重现出来。由此得到的相位谱与从传递函数的解析表达式直接计算的相位谱满意地符合。由此推论,如果已知换能器是最小相位系统,则它的传递函数的相位谱可以利用希尔伯特变换从它的振幅谱的测量值重现出来,考虑到相位谱实际测量的种种困难,而振幅谱的测量则十分简便,因此相位谱的重现具有很重要的实际意义。

     

    Abstract: In this paper, under Kirchhoff's assumptions, a theory of the thin shell o'f radially-polarized piezoelectric ceramic cylinder has been developed. Using the methods of the Green's function and separation of variables the scattering of a plane wave by the cylinder has been solved. The normal mode series expressions of the velocity distribution of the surface of the cylinder and of the total sound field have been obtained and from those an exact analytical expression of the transfer function of the cylinder as a sound receiver has been given. Arbitrary transient response of the cylinder can be calculated from the transfer function by using FFT.
    For PZT-5 piezoelectric ceramic cylinder, the transfer function, impulse response and step response have been calculated. The results show that the impluse response appears a typical minimum phase behaviour and so the cylindrical piezoelectric receiver belongs to the minimum phase system. Therefore, the phase spectrum of transfer function of the receiver can be reconstructed from its amplitude spectrum by using the Hilbert transform. The phase spectrum obtained by such a method is in good agreement with that calculated from the analytical expression of transfer function directly.
    Obviously, it can be deduced that if a transducer has the minimum phase property then the phase spectrum of its transfer function can be reconstructed from the measured values of the amplitude spectrum by using the Hilbert transform.
    The phase reconstruction of transducer is of importance in engineering applications, especially because o’f various difficulties of the phase measurement.

     

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