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  直接序列扩频系统（DS，Direct Sequence）又称为直接序列调制系统或伪噪声系统（PN 系统），简称为直扩系统，是目前应用较为广泛的一种扩展频谱系统。要传送的信息经伪随机序列编码后对载波进行调制。在发信端越冬用扩频序列去扩展信号的频谱，在收信端，用相同的扩频友序列进行解扩，将展宽的频谱扩展信号还原成原始信号。因为伪随机序列的速率远大于要传送信息的速率，所以受调信号的频谱宽度将远大于要传送信息的频谱宽度，帮称之为扩频(Direct sequence spread spectrum (DS, Direct Sequence) modulation system, also known as direct sequence or pseudo-noise system (PN system), referred to as direct expansion systems, is currently the more widely used as a spread spectrum system. To send the information encoded by the pseudo-random sequence of carrier modulation. End of winter in the letter to extend the signal with the spreading sequence of spectrum, in the end prepared to receive and use the same sequence spread spectrum despreading friends, broadening the spectrum to restore the original signal expansion signals. Because the rate of pseudo-random sequence is much larger than the rate of information to be sent, so the frequency spectrum by adjusting the width of the spectrum is much larger than the width of the information to be sent to help is called spread spectrum)