Piezoelectric signals of layered systems driven by elastic waves

An incident elastic wave propagating in a cubic piezoelectric multilayer system, along to the direction of growth, and the reflected elastic wave in the system form an elastic standing wave inside after interference. The elastic standing wave induces a standing wave of strains, which results in a standing wave of piezoelectric fields. The field will produce an AC voltage signal across the system at the frequency of the elastic wave. The sensitivity of the piezoelectric signal depends on the number of the period. The maximum of the crests of the voltage signal appear when the wavelength is equal to a value of 1/odd number comparing with thickness of each period, and if the thickness of one period is smaller than the wavelength, no maximum peak appears