Application Cases

Experiment Name: Application of Power Amplifiers in Flexural Wave Acoustic Lens Focusing Experiments

Experimental Content:
To test whether flexural waves can reach a focal point after reflection by adjacent acoustic lenses, thereby achieving energy harvesting.

Research Direction: Study of elastic wave propagation mechanisms in phononic crystals

Testing Equipment: Signal generator, ATA-2022B high-voltage amplifier, longitudinal wave straight probe, PZT, oscilloscope, computer, etc.

Experimental Procedure:
First, two adjacent lenses were designed based on Mindlin plate theory and phase modulation principles. Theoretical and numerical simulations demonstrated that flexural waves would focus within a specific region, with a focal spot size smaller than half the wavelength. To validate this design concept, acoustic lenses were machined along the edges of an aluminum plate, and a PZT array was arranged in the excitation region. All PZT elements were connected in parallel to the circuit.

Although the PZT elements themselves have high energy conversion efficiency, driving the entire array simultaneously required signal amplification via a power amplifier. In this experiment, the ATA-2022B high-voltage amplifier was selected, which amplified the output voltage by a factor of 20 before delivering it to the PZT array, providing sufficient voltage to drive all 17 piezoelectric ceramic elements simultaneously. The excitation signal was a narrowband pulse with a center frequency of 25 kHz, enabling optimal amplification.

On the receiving end, a longitudinal wave straight probe was used to collect signals point by point in the detection region. The oscilloscope was connected to a computer for batch processing. Finally, all collected signals were transformed into the frequency domain via Fourier transform to qualitatively characterize the focusing behavior of flexural waves and compare the results with simulations.

Schematic of the plate combining two lenses for focusing incident flexural waves:
(a) Schematic of the lenses; (b) Theoretical model of the base plate.

Rectangular aluminum plate and experimental system: The rectangular aluminum plate was fabricated with two lenses placed at the corners.

Experimental Results:
The flexural wave focusing phenomenon was distinctly observed. The actual focal position (0.101 m, 0) closely matched the theoretical design value (0.1 m, 0). The focal spot dimensions were 1.92 cm and 1.40 cm in the x- and y-directions, respectively, corresponding to 0.57λ and 0.42λ. The focal spot size in the y-direction being smaller than half the wavelength indicates subwavelength focusing.

Squared received voltage after FFT: (a) Near the theoretical focal position; (b) Along the x-direction at y = 0; (c) Along the y-direction at x = 0.101 m.

Figure: ATA-2022B High-Voltage Amplifier Specifications and Parameters