Ultrasonic Barker-coded excitation method with attenuation matching

In order to increase the ability of ultrasound to penetrate the high attenuation medium,an attenuation matching method of ultrasonic Barker-coded excitation is proposed.Based on the assumption of transducer impulse response with Gaussian shape and linear phase attenuation without dispersion in material,the signal model of Barkercoded excitation is obtained.By solving the expression of signal-to-noise ratio of Barker-coded pulse compression after sidelobe suppression,it can be seen the proposed method only needs to adjust the center frequency and time duration of the Barker-coded signal according to the material attenuation characteristic and the requirement of axial resolution.Take the rubber with attenuation coefficient of 1.4 Np/(MHz·cm) and thickness of 5 cm for example.When the axial resolution of square wave excitation method is similar to that of the Barker-coded excitation method,the signal-to-noise ratio gain of attenuation matching Barker-coded excitation method is nearly 5 dB higher than that of traditional Barkercoded excitation method.Furthermore,the increasement of the signal-to-noise ration gain grows to 11 dB at the cost of the axial resolution.The results show that the attenuation matching Barker-coded excitation method can reduce the influence of frequency-dependent attenuation on pulse compression and effectively improve the signal-to-noise ratio of the attenuated echo.