Application Cases

Experiment Name: Application of High-Voltage Amplifiers in Research on HIFU Transducers and Sound Field Measurement

Research Direction: Medical Ultrasound

Test Objective:
The HIFU sound field possesses unique acoustic characteristics, requiring that the detection method avoids interference with the sound field while also withstanding the impacts caused by high temperature, high pressure, and cavitation responses. Currently reported methods have certain limitations in terms of application scope, measurement upper limit, anti-interference capability, and accuracy. Therefore, a sound field calculation model based on the Rayleigh integral is proposed. According to this calculation principle, the sound field distribution can be described by obtaining the normal vibration velocity distribution of all particles on the radiating surface of the HIFU transducer. Based on this, considering the characteristics of the vibration velocity distribution on the transducer surface, a measurement method for the transducer's surface normal vibration velocity is established. An all-fiber Doppler vibrometer system based on a fiber optic vibration sensor is investigated, ultimately achieving the measurement of transducer surface vibration velocity, sound pressure measurement of the HIFU field, and description of the sound field distribution.

Test Equipment: ATA-2041 high-voltage amplifier, signal generator, photodetector, oscilloscope, piezoelectric ceramic under test, all-fiber Doppler vibrometer system.

Experimental Procedure:

Figure: Experimental Setup of the All-Fiber Doppler Vibrometer System Based on a Fiber Optic Vibration Sensor

During the experiment, the object under test was initially kept stationary. The fiber optic vibration sensor was positioned above the piezoelectric ceramic. The laser was turned on, and the signal generator output was set to a sinusoidal signal of 5V with a 2.5V offset. When the signal generator started outputting, the amplification factor of the power amplifier was continuously adjusted. The vibrometer system obtained an interferometric output electrical signal containing the vibration signal of the piezoelectric ceramic via the AC output port of the photodetector, which was then displayed on an oscilloscope.

Based on the relationship between the maximum measurable velocity and the delay time in the system testing, the velocity measurement range corresponding to the fiber delay line length was relatively large. However, in this experiment, the vibration velocity of the piezoelectric ceramic was relatively small. Therefore, the delay time was initially set to 50 ps, the laser output wavelength to 1550 nm, and the driving signal was set to the resonant frequency of the piezoelectric ceramic.

Experimental Results:

Figure 2: Interference Signal Output from the All-Fiber Doppler Vibrometer System at 20V Driving Voltage

Figures 2(a), (b), and (c) show the interference signal output curve, amplitude-frequency curve, and phase-frequency curve of the all-fiber Doppler vibrometer system at a driving voltage of 20V, respectively.

Figure 3: Interference Signal Output from the All-Fiber Doppler Vibrometer System at 30V Driving Voltage

Figures 3(a), (b), and (c) show the interference signal output curve, amplitude-frequency curve, and phase-frequency curve of the all-fiber Doppler vibrometer system at a driving voltage of 30V, respectively.

From the obtained interference signals, the vibration velocity of the piezoelectric ceramic measured by the vibrometer system under the corresponding driving voltage conditions can be demodulated. According to the signal processing method, the Doppler shift carried by the vibration signal measured at 20V driving voltage, processed by the computer, was 74.84 kHz, corresponding to a vibration velocity of 58 mm/s. The Doppler shift at 30V driving voltage was 125.16 kHz, corresponding to a vibration velocity of 97 mm/s.

The experimental results demonstrate the feasibility of applying the all-fiber Doppler vibrometer system based on a fiber optic vibration sensor for measuring the surface vibration velocity of piezoelectric ceramics.

Figure: ATA-2041 High-Voltage Amplifier Specifications and Parameters