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本文讨论了直接序列扩展频谱系统在几种不同类型干扰下的性能,提出用“系统增益”作为扩谱系统与普通系统性能比较的准则。通过对解扩相关器输出的干扰功率谱的计算,得出了系统增益的表达式,从而明确了扩谱系统的主要好处是:在不牺牲白噪声干扰下的性能的前提下,改善了通信的荫蔽性,得到了抗窄带干扰和多径干扰的能力。本文还从同步误差引起的信号能量损失及相关自噪声这两个方面进行了计算,并从减小自噪声的角度对 PN 码周期的选择提出了设计原则。附录中给出了 PN 序列的自相关函数 R_c(τ)(τ为连续值)的证明。
In this paper, the performance of direct sequence spread spectrum system under several different types of interference is discussed. It is proposed that “system gain” be used as a criterion for performance comparison between spread spectrum systems and ordinary systems. Through the calculation of the interference power spectrum output from the despreading correlator, the expression of the gain of the system is obtained, and the main benefit of the spread spectrum system is clarified: the communication is improved without sacrificing the performance under white noise interference Of shading, get the resistance to narrow band interference and multipath interference. In this paper, the signal energy loss caused by synchronization error and the related self-noise are calculated. The design principle of PN code period is proposed from the view of reducing the self-noise. The appendix shows the proof of the autocorrelation function R_c (τ) (τ is a continuous value) of a PN sequence.