伪随机码宽带扩频技术在海洋探测中的应用

发布时间：2019-07-07 20:21

【摘要】：本文主要研究伪随机码宽带扩频探测技术在海洋中的应用,针对目前国内外常用的典型水声探测技术与设备的一些不足之处,提出利用伪随机码宽带扩频技术改善现有的海洋探测系统性能。本文首先对扩频技术理论做了深入的讨论,认识到扩频技术对于信号信噪比的改善。伪随机码序列为伪随机扩频系统的发射信号,因而伪随机码的设计对系统性能具有重要的影响,此外,当有多个系统平台观测时,伪随机码还可作为码分多址技术中的地址码使用。本文的伪随机码以Gold序列为主,而Gold序列是基于m序列优选对产生的,因而本文讨论和探索了m序列和Gold序列的生成条件,并对其相关特性进行比较,最终设计出适合扩频系统平台的平衡Gold序列码集。扩频技术中信号在接收端要达到最大信噪比,则需要一种最佳的线性滤波器,这就需要匹配滤波来实现,因而本文还讨论了匹配滤波的原理算法及其在时域和频域的实现,并在频域上实现了Gold序列的匹配滤波处理。扩频技术的实现需要借助于数字信号处理器(DSP)平台,因而本研究利用数字信号处理器、模数/数模转换器、内存等硬件搭建了一海洋探测泛用的数字信号处理器平台,并将信号生成程序和匹配滤波程序写入该平台中,成为扩频技术的核心处理器。为验证伪随机码扩频技术对海洋探测系统性能的改善,在实验室环境下通过发射Gold序列、Chirp信号和CW信号,并在接收端接收这些信号,利用DSP中的匹配算法分别对其这三种信号进行匹配处理,并评价这三种信号的匹配处理对系统性能的影响。结果表明6阶的Gold序列具有和Chirp信号相近的系统处理增益,它们的增益比CW信号高得多,而Gold序列具有最佳的时间分辨率。此外,将数字信号处理器海洋泛用平台运用于海洋声层析系统中,通过声层析系统实现扩频技术在实际海洋探测中的应用。计划在舟山桃花岛海域布设声层析基站,选取目标海域的声层析布设点,完成声层析基站的设计,并对目标海域进行水文调查并对该海域的声学环境进行分析,为实际海域系统测试和之后的长期声层析声呐系统的观测提供实际海域的声学环境数据支撑。
文内图片：

图片说明：阶m序列自相关函数曲线
[Abstract]:In this paper, the application of pseudorandom code broadband spread spectrum detection technology in ocean is studied. In view of some shortcomings of typical underwater acoustic detection technology and equipment commonly used at home and abroad, the performance of existing marine detection system is improved by using pseudorandom code broadband spread spectrum technology. In this paper, the theory of spread spectrum technology is discussed in detail, and the improvement of signal-to-noise ratio (SNR) by spread spectrum technology is recognized. Pseudorandom code sequence is the transmitted signal of pseudorandom spread spectrum system, so the design of pseudorandom code has an important influence on system performance. In addition, pseudorandom code can also be used as address code in code division multiple access (CDMA) technology when there are multiple system platforms. In this paper, the pseudorandom code is mainly Gold sequence, while Gold sequence is based on m sequence optimization pair. Therefore, this paper discusses and explores the generation conditions of m sequence and Gold sequence, compares their related characteristics, and finally designs a balanced Gold sequence code set suitable for spread spectrum system platform. In order to achieve the maximum signal-to-noise ratio (SNR) at the receiver of spread spectrum technology, an optimal linear filter is needed, which requires matching filtering. Therefore, the principle and algorithm of matched filtering and its implementation in time domain and frequency domain are also discussed in this paper, and the matched filtering processing of Gold sequence is realized in frequency domain. The realization of spread spectrum technology needs the help of digital signal processor (DSP) platform, so this research uses digital signal processor, analog-to-digital converter, memory and other hardware to build a universal digital signal processor platform for ocean detection, and writes the signal generation program and matching filter program into the platform, which becomes the core processor of spread spectrum technology. In order to verify the improvement of the performance of marine detection system by pseudorandom code spread spectrum technology, Gold sequence, Chirp signal and CW signal are transmitted in laboratory environment, and these signals are received at the receiving end. The matching algorithm in DSP is used to match the three signals, and the influence of matching processing of these three signals on the performance of the system is evaluated. The results show that the sixth order Gold sequence has the same system processing gain as the Chirp signal, and their gain is much higher than that of the CW signal, while the Gold sequence has the best time resolution. In addition, the offshore universal platform of digital signal processor is applied to the ocean acoustic tomography system, and the application of spread spectrum technology in the actual ocean detection is realized by the acoustic tomography system. It is planned to set up acoustic chromatography base station in Zhoushan Taohua Island sea area, select the acoustic chromatography distribution point in the target sea area, complete the design of acoustic chromatography base station, and carry on the hydrological investigation to the target sea area and analyze the acoustic environment of the sea area, so as to provide the acoustic environment data support for the actual sea area system test and the long-term acoustic tomography Sonar system observation.
【学位授予单位】：浙江海洋大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P715

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