从*.dat文件保存的4根天线数据中提取出前两根天线的数据，并保存在文件中-*. Dat file from the four antennas to extract the data before the two antenna data, and save the file

chu序列的同步应用，用于帧同步，提取数据起点-Application of Chu sequence for synchronization, frame synchronization, data extraction point