说明：  这是直接扩频通信系统的PPT课件，清楚讲解了扩频技术的来源，理论依据等，让人能快速了解扩频技术的原理。
(This is a direct spread spectrum communication system, PPT courseware, clearly explained the source of spread spectrum technology, the theoretical basis so people can quickly understand the principle of spread spectrum technology.)