说明：  本文是在学习了数字信号处理课程之后，通过阅读了近几年的一些文章，结合自己的方向GPS数据处理，写的一篇总结文章。其中主要主要篇幅介绍了两种载波L1和L2，GPS伪噪声码，以及调制过程。
(This article is in learning digital signal processing course after reading some articles in recent years, combined with the direction the GPS data processing, write a summary of articles. Which mainly length introduces two carrier L1 and L2, and the GPS pseudo noise code, and a modulation process.)