Ultrashort pulse generation of airborne ultrasound by harmonic pulse compression using nonlinear focused ultrasound for ultra-high-precision airborne ultrasound sensing

Abstract The prolonged duration of radiated sound waves is one of the most challenging issues hindering the utilization of airborne ultrasound sensing. Here, we propose a signal processing method using nonlinear focused ultrasound and pulse compression techniques. Nonlinear focused ultrasound generates harmonics that are integer multiples of the driving signal frequency, enabling the radiation of broadband sound waves. On the other hand, since the frequency band of ultrasound waves containing harmonics is discrete, applying pulse compression generates sidelobes, which reduces the effectiveness of pulse compression. Therefore, by applying phase compensation, frequency interpolation and pulse compression techniques to these waves, it becomes possible to achieve extremely short-pulse sound radiation through signal processing. Specifically, this method succeeded in shortening the pulse width to 1/15 of that of conventional methods.