Application Cases

Experiment Name: Application of Power Amplifiers in Underwater Acoustic Radiation Experiments Based on Flexible Piezoelectric Ultrasonic Transducers

Experiment Objective:
To address the long-term needs for adjunctive treatment of bone injuries,  attachable flexible piezoelectric ultrasonic transducer was designed.

Experimental Equipment:
Host computer, signal generator, power amplifier, hydrophone, test water tank

Experimental Content:
Test clamping platform)was controlled by a stepper motor to achieve displacement along the X, Y, and Z axes. A signal generator and a power amplifier served as the excitation source, providing a sinusoidal excitation signal to the flexible piezoelectric ultrasonic transducer. A hydrophone fixed in position was used to receive the underwater ultrasonic waves emitted by the flexible piezoelectric ultrasonic transducer. The received signals were fed back to the host computer via an oscilloscope for data acquisition.

Experimental Procedure:
In this test, a sinusoidal voltage with a frequency of 321.15 kHz (the device's resonant frequency previously measured in water using an impedance analyzer) and an amplitude of 10 V was initially used as the excitation signal for the flexible piezoelectric ultrasonic transducer, driven by a power amplifier. The distance between the hydrophone and the flexible piezoelectric ultrasonic transducer was controlled to be 5 cm (the minimum achievable distance due to equipment assembly constraints), and the receiving end of the hydrophone was aligned with the center of the device under test.

The black waveform represents the signal generated by the signal generator, while the blue waveform is the signal received by the hydrophone. As shown in the figure, the peak-to-peak voltage of the ultrasonic signal received by the hydrophone was 31 mV. However, without changing the relative position of the hydrophone and the flexible piezoelectric ultrasonic transducer or the excitation voltage amplitude, the frequency of the sinusoidal excitation was repeatedly varied. It was observed that the intensity of the ultrasonic signal received by the hydrophone was maximum at a frequency of 357 kHz.

Figure: Excitation Signal Waveform and Received Voltage Waveform at 321.15 kHz

Figure: Excitation Signal Waveform and Received Voltage Waveform at 357 kHz

Experimental Results:
The calculated relationship between the excitation voltage amplitude and the ultrasonic acoustic intensity is shown in the figure. It can be observed from the figure that when the sinusoidal excitation signal had a frequency of 357 kHz and an amplitude of 100 V, the signal measured by the hydrophone at a distance of 5 cm from the flexible piezoelectric ultrasonic transducer was calculated to yield an acoustic intensity of 55.33 W/m², equivalent to 5.533 mW/cm². Due to the minimum controllable distance in this experiment being 5 cm rather than complete attachment, the measured acoustic intensity was relatively low. However, the current experimental data indicate that the low-intensity ultrasound generated by the flexible piezoelectric ultrasonic transducer has the potential to assist in the treatment of bone fractures. Its safety depends on the amplitude of the excitation voltage and the duration of exposure.

Figure: Relationship Between Ultrasonic Acoustic Intensity and Excitation Voltage Amplitude

Figure: ATA-4011C High-Voltage Power Amplifier Specifications and Parameters