直接序列扩频系统是在发端直接用具有高码率的扩频编码去扩展信号的频谱，而在收端用相同的扩频编码进行解扩使扩频信号还原为原始信号的一种扩频方式。直接序列系统中用的编码序列通常是伪随机序列或叫伪噪声（PN）码。要传送的信息经数字化后变成二元数字序列，它和伪随机序列模二相加(或相乘)后变成复合码去调制载波。在直接序列系统中通常对载波进行二进制相移键控调制(BPSK)。当扩频调制后由天线发射出去，在接收机中要有一个和发射机中的伪随机码同步的本地码，对接收信号进行解扩，解扩后的信号送到解调器取出传送的信息-direct sequence spread spectrum system is the originator directly with the high rate of spread spectrum signal coding to the expansion of the spectrum, and the resumption end with the same spread-spectrum coding for despreading spread spectrum signal so that the original signal reverted to a spread-spectrum approach. Direct-sequence system used in the coding sequence is usually pseudo-random sequence, or a pseudo-noise (PN) code. To the transmission of digital information by the following figures into binary sequence, it, and pseudo-random sequence-two together (or multiplication) into a composite code modulation to Carrier. In the direct-sequence system usually right carrier for binary phase shift keying modulation (BPSK). When spread spectrum modulation after the antenna launched, in the