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由于超声波能对人体内部组织无创伤地进行探测,近年来,超声实时显象在医学上获得了越来越广泛的应用,B型超声显象成了一种有效的常规检查手段.因此,对超声接收机进行深入的研究,以获得更好的图象质量,是有意义的. 超声在生物介质中传播时,由于组织的吸收、散射、反射,强度急剧减弱,其衰减系数与超声频率有关,频率越高,衰减越快,因此其中心频率就随传播距离增加而向低处迁移.有许多文献都谈到过这个现象,但未曾见到有关该现象的定量计算. 本文论证了在高斯形脉冲情况下,频率迁移的一般规律,提出了定量公式,并且具体设计了迁频接收机,得到了较好的实验效果.
In recent years, ultrasound real-time imaging has been more and more widely used in medicine, and ultrasound B imaging has become an effective routine examination method. Ultrasound receiver in-depth study to obtain better image quality, it is significant.Ultrasound in biological media, due to tissue absorption, scattering, reflection, the intensity of the abrupt decline, the attenuation coefficient and the ultrasonic frequency , The higher the frequency, the faster the attenuation, so its center frequency with the propagation distance increases to the lower migration.Many literatures have talked about this phenomenon, but did not see the quantitative calculation of this phenomenon.This paper demonstrates that Gaussian Shape pulse, the general rule of frequency migration, a quantitative formula is proposed, and the concrete design of the frequency shift receiver, get better experimental results.