Equivalent transmission line characterization and multi-layer material measurement analysis of the signal conversion process in the pulsed electro-acoustic method

This paper studies the equivalent transmission line model of the pulsed electro-acoustic (PEA) method with its applications. Based on the consistency of acoustic wave behaviour inside lossy acoustic materials and voltage wave propagation in transmission line, an equivalent simulation model of the PEA system is developed, whose reliability is verified by the output from the transducer and amplifier models and the comparison with measured waveforms. For the problem of acoustic impedance mismatch between different modules, simulation indicates that the unequal impedances of semiconducting electrode and sample can affect the amplitude of the measured signal at the upper electrode side, and the reflected acoustic waves caused by the transducer can affect the charge waveform. Further simulation for multi-layer materials finds that the reflected acoustic waves of different samples and sound absorbing module can superimpose on the charge signal. Accordingly, a selection criterion is proposed to avoid the effect of the reflected waves at the interface. As for the acoustic reflection caused by internal charge, it needs to be dealt with sequentially in calibration process, starting from the result inside the sample near ground electrode. The research can provide a foundation for analyzing the acoustic properties of the PEA method. The acoustic wave propagation in the pulsed electro-acoustic (PEA) method can be equivalent to the voltage wave behaviour in the transmission line model. Based on the model, it is found that the acoustic impedances of the PEA modules can affect the amplitude and shape of the measured charge waveforms severely. A selection criterion is then proposed to avoid the superimposition effect of the reflected waves at the interfaces of the multi-layer samples and sound absorbing module.image