中文说明：这个程序可以将超声射频信号读取并且分成若干帧，最终以文本文档的形式保存。读取的信号格式为RFD文件，若读取失败返回值为-1.同时文件还可以保存为.mat文件，在Matlab中使用非常方便
English Description：
This procedure can be read and the ultrasonic radio frequency signal into a number of frames, stored in the form of the final text document. RFD signal format file is read, the return value is -1 if the read fails while .mat files can also be saved as a file, very easy to use in Matlab