中文摘要：

由于生物软组织对超声波的衰减、吸收等作用，组织超声背散射射频（RF）信号的中心频率会发生偏移，利用超声背散射RF信号中心频率的偏移量来估计软组织超声特征散射子的粒径等特征成为可能。该文在软组织超声背散射RF信号功率谱理论分析的基础上，制作了4种不同散射子粒径的实验仿体，并对实验仿体进行了信号采集和数据处理，研究其频率特性。研究结果表明，生物软组织超声背散射RF信号的中心频率随超声特征散射子粒径的增大而向低频方向移动，且越来越接近发射超声信号的中心频率。

英文摘要：

Due to the effects of ultrasonic attenuation and absorption by biological soft tissue, central frequency of ultrasonic backscattered radio frequency（RF）signals will be offset, and it is possible to use the offset of central frequency to estimate the features of scatterer in the soft tissues, such as scatterer size, and so on. Based on the theoretical analysis of power spectrum of ultrasonic baekscattered RF signals, this paper has made four experimental imitations which have different scatterer sizes, and conducted a signal acquisition and processed the data for the experimental imitations to study the frequency characteristics. The results of research show that the central frequency of ultrasonic backscattered RF signals will trend to low-frequency when the size of ultrasonic feature scatterer is increased, getting more and more closer to the central frequency of launch ultrasonic signal.