摘要
扩展频谱通信作为新型的通信方式,由于其优良的多址接入、低截获概率、抗干扰和强保密等特性,使得它在军事通信、卫星通信和C 3I等系统中得到了广泛的应用。为取得现代电子战的胜利,对扩频通信的有效干扰成为关键。因此,针对应用最广泛的直接序列扩频、跳频扩频通信系统进行了干扰研究具有重要的现实意义。
本文深入研究了直接序列扩频、跳频扩频通信系统抗干扰原理及对其干扰措施,主要工作包含:直接序列扩频通信系统DS/DPSK的建模与仿真、FH/BFSK跳频扩频系统的建模与仿真;以及针对DS/DPSK、FH/BFSK系统中干扰模块的设计与仿真,同时对一种特定的卫星链路和对FH/DPSK系统的一种相位估计算法进行了仿真研究。
对于DS/DPSK直接序列扩频的数字接收系统中的载波跟踪和伪码跟踪的方法,通过对其数学模型和参数设计进行分析,建立在simulink下的动态系统仿真模型,通过仿真实验验证了数学模型的正确性及仿真输出结果能准确的反映实际系统的性能,在进行分析的同时建立了干扰模型并在仿真模型上进行了干扰仿真,该部分主要工作如下:
研究了利用科斯塔斯环进行载波同步跟踪的方法和超前/滞后非相干延迟锁相环进行伪码跟踪的方法,分别对其数学模型和参数设计进行了分析,建立了跟踪环路仿真模块,进行了仿真实验,并与理论分析结果进行了比较。
对直扩系统的最佳干扰带宽、最佳干扰频率进行了数学分析,在已建立的DS/DPSK仿真模型上进行了仿真实验,与数学分析结果进行比较。对一种特定的卫星数据链路进行了干扰建模仿真,证实了脉冲干扰较单音干扰具有高效性。
对于跳频扩频的捕获和跟踪,对其数学模型进行分析,建立了捕获、跟踪及系统仿真模型,在系统模型上进行了多种干扰样式仿真实验,仿真实验验证了系统模型的正确性及对其干扰的有效性,该部分主要工作如下:
研究了基于匹配滤波器的跳频序列并行捕获技术,对并行捕获技术进行了数学分析和建立了仿真模型,同时建立了基于超前/滞后非相干延迟锁相环的FH/BFSK的扩频通信系统,对捕获和FH/BFSK系统都进行了仿真实验,得到与理论一致的结果。
对FH/BFSK进行了干扰分析,在仿真平台上对FH/BFSK系统进行了噪声干扰、多音干扰分析与仿真,证实了多音干扰较噪声干扰节省干扰功率。同时研究了针对FH/DPSK系统的一种相位估计算法,用该算法来估计每一跳信号的相位,相位校正后减少了FH/DPSK系统相位误差导致的功率损失。
As a novel communication mode, the spread spectrum communications are widely used in military communications, satellite communications and C 3I (Command, Control, Communications & Intelligence) system because of its well multi address access, low probability interception, the excellent performance of anti-interference and secrecy. The effective jamming for spread spectrum communications systems becomes the key to get the victory of electronic war, so it is very important to research the effectiveness of jamming and interference referred to the direct sequence spread spectrum (DS-SS) and frequency hopping spread spectrum communication system.
In this dissertation, DS-SS, FH-SS system are profoundly studied. Many kinds of effective jamming on them are founded out. The main work includes: The study of the key techniques in both DS/DPSK system and FH/BFSK system, the modeling and simulation of them; the evaluation and simulation of various jamming on them respectively and the study of a phase estimation algorithm for FH/DPSK system.
In the first part, the techniques of Costas carrier tracking and non-coherent PN sequence tracking in digital receiver for DS/DPSK system are studied. The dissertation analyzes its mathematical models and design of parameters, and finishes its simulative model on simulink platform. Through the experiment, the dissertation testifies that the mathematical model is correct and simulation results can approximately reflect the performance of real system.
The optimum jamming bandwidth and optimum jamming frequency for DS system are mathematically analyzed. The simulative experiment is carried out on the DS/DPSK model. Then the dissertation compares the theoretical analyses and the computer simulation results, and testifies the correctness of these analyses. In the meanwhile, the modeling and simulation of jamming for a specific satellite communication data link are finished. The simulation results indicate that the pulse jamming is more efficient than single-tone jamming.
The dissertation studies a parallel acquisition algorithm based on matched filters for FH-SS system and finishes modeling and simulation on simulink, then builds non-coherent tracking simulation model for FH/BFSK. The simulation results are consistent with the theoretical analyses.
The effectiveness of broadband noise, partial bandwidth noise and multi-tone jamming are deeply studied. The jamming simulation experiment is carried out on the FH/BFSK model. Then the dissertation compares the theoretical analyses and the computer simulation result, and testifies multi-tone jamming is more efficient than noise jamming. Finally, this dissertation studies a phase estimation algorithm for FH/DPSK system, using it to estimate the phase of each hop to gain more power efficiency.
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