DSSS系统的干扰检测技术研究与实现
发布时间：2018-09-14 06:45
【摘要】：无线通信发展至今,已经广泛应用于各个领域,但空间电磁环境复杂多变,通信系统的可靠性依然受到空间干扰的威胁。基于扩频技术的直接序列扩频(DSSS)系统的抗干扰性强、保密性高、截获概率低,成为现今众多通信系统中最常用的通信系统并应用到各个领域。虽然DSSS系统可以在具有一定干扰存在的空间环境中正常工作,但当干扰信号的强度超过系统干扰容限时,系统通信的可靠性将无法得到保证,通信抗干扰技术是保障通信可靠性的必要途径,而干扰检测技术是通信抗干扰技术的基础也是关键技术,因此,针对DSSS系统干扰检测技术的研究具有重要的现实意义。首先,本文介绍了DSSS系统和干扰检测技术的基本原理、干扰门限的选取方法和虚警概率的计算,为DSSS系统干扰检测技术的研究奠定了理论基础。其次,对DSSS系统中常见的干扰信号进行了建模、分析,并给出了信号的数学表达式。详细研究了干扰检测技术中常用的频域干扰检测算法:一般干扰检测算法、连续均值去除算法(CME)、前向连续均值去除算法(FCME)、双门限算法。最终改进了FCME算法,运用MATLAB仿真了窗函数对算法干扰检测性能的影响和不同干扰检测算法之间检测性能的差异。通过仿真、分析、比较可知,在同一检测概率下,使用汉明窗(Hamming)的改进FCME算法比其他几种算法的整体检测性能更好。最后,利用FPGA对改进FCME算法进行硬件实现,设计出干扰检测通信系统,并在静默周期和非静默周期下,分别测试了系统对单音干扰、多音干扰以及窄带干扰的检测性能。测试结果表明,改进FCME算法的实际检测性能与运用软件仿真时的检测性能接近,信号的信噪比不同,系统对干扰信号的检测性能也不一样。在静默周期下,系统能够对干噪比大于-30d B的单音干扰信号、干噪比大于-26d B的多音干扰信号以及干噪比大于-4d B的窄带干扰信号正确检测出频点的位置。在非静默周期下,信噪比为-15d B时,系统能够对干噪比大于-29d B的单音信号、干噪比大于-24d B的多音信号以及干噪比大于-3d B的窄带信号正确检测出频点的位置。信噪比为0d B时,系统能够对干噪比大于-23d B的单音信号、干噪比大于-18d B的多音信号以及干噪比大于2d B的窄带信号正确检测出频点的位置。该干扰检测通信系统对常见类型的干扰信号表现出很好的检测性能。
[Abstract]:Since the development of wireless communication, it has been widely used in various fields, but the electromagnetic environment in space is complex and changeable, and the reliability of communication system is still threatened by space interference. The direct sequence spread spectrum (DSSS) system based on spread spectrum technology has strong anti-interference, high security and low probability of interception. It has become the most commonly used communication system in many communication systems and has been applied to various fields. Although the DSSS system can work normally in the space environment where the interference exists, the reliability of the system communication will not be guaranteed when the intensity of the interference signal exceeds the interference tolerance limit of the system. The communication anti-jamming technology is the necessary way to guarantee the communication reliability, and the interference detection technology is the foundation and the key technology of the communication anti-jamming technology. Therefore, it is of great practical significance to study the interference detection technology of the DSSS system. Firstly, this paper introduces the basic principle of DSSS system and interference detection technology, the selection method of interference threshold and the calculation of false alarm probability, which lays a theoretical foundation for the study of interference detection technology in DSSS system. Secondly, the common interference signals in DSSS system are modeled, analyzed, and the mathematical expressions of the signals are given. The frequency-domain interference detection algorithms commonly used in interference detection are studied in detail: general interference detection algorithm, continuous mean removal algorithm, (CME), forward continuous mean removal algorithm, (FCME), double threshold algorithm. Finally, the FCME algorithm is improved, and the influence of window function on the performance of interference detection and the difference between different algorithms are simulated by MATLAB. Through simulation and analysis, we can see that under the same detection probability, the improved FCME algorithm using hamming window (Hamming) has better overall detection performance than other algorithms. Finally, the improved FCME algorithm is implemented by using FPGA, and the interference detection communication system is designed, and the detection performance of monophonic interference, multi-tone interference and narrowband interference is tested under silence period and non-silence period, respectively. The test results show that the actual detection performance of the improved FCME algorithm is similar to that of the software simulation. The signal-to-noise ratio of the signal to noise is different, and the detection performance of the interference signal is not the same. In the silent period, the system can correctly detect the position of the frequency points for the single tone interference signal with a dry noise ratio greater than -30 dB, the multi-tone interference signal with a dry noise ratio greater than -26 dB and the narrow band interference signal with a dry noise ratio greater than -4 dB. When the signal-to-noise ratio (SNR) is -15dB, the system can correctly detect the position of the frequency points for the single-tone signal with a signal-to-noise ratio greater than -29dB, the multi-tone signal with a dry-noise ratio greater than -24dB and the narrow-band signal with a signal-to-noise ratio greater than -3dB. When the signal-to-noise ratio (SNR) is 0 dB, the system can correctly detect the position of the frequency point for the single tone signal with a signal-to-noise ratio greater than -23 dB, the multi-tone signal with a dry-noise ratio greater than -18 dB and the narrow band signal with a signal-to-noise ratio of more than 2 dB. The interference detection communication system has good detection performance for common types of interference signals.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN972
[Abstract]:Since the development of wireless communication, it has been widely used in various fields, but the electromagnetic environment in space is complex and changeable, and the reliability of communication system is still threatened by space interference. The direct sequence spread spectrum (DSSS) system based on spread spectrum technology has strong anti-interference, high security and low probability of interception. It has become the most commonly used communication system in many communication systems and has been applied to various fields. Although the DSSS system can work normally in the space environment where the interference exists, the reliability of the system communication will not be guaranteed when the intensity of the interference signal exceeds the interference tolerance limit of the system. The communication anti-jamming technology is the necessary way to guarantee the communication reliability, and the interference detection technology is the foundation and the key technology of the communication anti-jamming technology. Therefore, it is of great practical significance to study the interference detection technology of the DSSS system. Firstly, this paper introduces the basic principle of DSSS system and interference detection technology, the selection method of interference threshold and the calculation of false alarm probability, which lays a theoretical foundation for the study of interference detection technology in DSSS system. Secondly, the common interference signals in DSSS system are modeled, analyzed, and the mathematical expressions of the signals are given. The frequency-domain interference detection algorithms commonly used in interference detection are studied in detail: general interference detection algorithm, continuous mean removal algorithm, (CME), forward continuous mean removal algorithm, (FCME), double threshold algorithm. Finally, the FCME algorithm is improved, and the influence of window function on the performance of interference detection and the difference between different algorithms are simulated by MATLAB. Through simulation and analysis, we can see that under the same detection probability, the improved FCME algorithm using hamming window (Hamming) has better overall detection performance than other algorithms. Finally, the improved FCME algorithm is implemented by using FPGA, and the interference detection communication system is designed, and the detection performance of monophonic interference, multi-tone interference and narrowband interference is tested under silence period and non-silence period, respectively. The test results show that the actual detection performance of the improved FCME algorithm is similar to that of the software simulation. The signal-to-noise ratio of the signal to noise is different, and the detection performance of the interference signal is not the same. In the silent period, the system can correctly detect the position of the frequency points for the single tone interference signal with a dry noise ratio greater than -30 dB, the multi-tone interference signal with a dry noise ratio greater than -26 dB and the narrow band interference signal with a dry noise ratio greater than -4 dB. When the signal-to-noise ratio (SNR) is -15dB, the system can correctly detect the position of the frequency points for the single-tone signal with a signal-to-noise ratio greater than -29dB, the multi-tone signal with a dry-noise ratio greater than -24dB and the narrow-band signal with a signal-to-noise ratio greater than -3dB. When the signal-to-noise ratio (SNR) is 0 dB, the system can correctly detect the position of the frequency point for the single tone signal with a signal-to-noise ratio greater than -23 dB, the multi-tone signal with a dry-noise ratio greater than -18 dB and the narrow band signal with a signal-to-noise ratio of more than 2 dB. The interference detection communication system has good detection performance for common types of interference signals.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN972
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