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题名	数字平台上实现甚宽频带恒定束宽方法
作者	方华
学位类别	博士
答辩日期	2005
授予单位	中国科学院声学研究所
授予地点	中国科学院声学研究所
关键词	嵌套线列阵 宽带 恒定束宽
中文摘要	要测量海洋中低噪声的目标，必须提高被动声纳的处理增益，一种有效的途径是采用高空间处理增益的基阵。对于宽带声纳，需要设计恒定束宽波束成形器，使得基阵系统对应不同频率的入射信号具有相同的波束图。宽带恒定束宽方法是声纳信号处理里面很重要的部分，不断有新方法提出。本文详细研究了一种利用嵌套线列阵的宽带恒定束宽成形方法，并且讨论了这种波束成形方法在DSP数字平台上的实现方法。嵌套线列阵方法主要步骤如下：将整个宽频带按频率的倍数关系划分成几个倍频程，在每个倍频程上对应低、高频率分别构成长、短均匀线列阵，长阵的阵元间距是短阵的两倍，让民、短子阵的输出信号分别通过一组补偿滤波器后相加，即刘"不同的频率长短阵信号进行线形组合，得到在倍频程上恒定束宽的信号，接着通过带通滤波器，滤掉倍频程以外的信号，最后把各个倍频程的输出信号相加得到在整个宽带上恒定束宽的信号。恒定束宽方法的信号处理需要在数字平台上实现。我们采用了一些行之有效的方法，解决了在数字化过程中出现的儿个主要问题。（1）线性内插法实现了对离散的数字信号的准确延迟，解决了聚焦处理时不能准确延迟数字信号的问题；（2）对信号进行降采样，解决了所需的带通滤波器通带太小、设计困难的问题；（3）设计与模拟滤波器有尽可能相习黝幅频响应的FIR滤波器，解决了理论方法中的模拟滤波器不能直接用来处理数字信号的问'题；（4）通过延迟点数消除处理过程中FIR滤波器带来的延迟，解决了各个倍频程的输出信号不同步，不能直接相加的问题。宽带恒定束宽方法运算量很大，为了提高整体计算速度，我们采用了可以多任务同时处理的DSP信号处理板。针对宽带恒定束宽方法的算法结构，进行了多任务可以同时处理的软件设计，实现了高速、高性能的数字信号处理，基本满足了声纳信号需高速处理的要求。
英文摘要	We must increase the gain of the passive sonar for measuring the object which radiates very low noise in ocean. An effective way is to use a sensor array which has high dimensional gain. It is needed to design a beamformer which can maintain the beamwidth of a transducer constant over a very wide frequency range for the directivity pattern at different frequency should be the same. The beamfomer is a very important part of the signal processing of the passive sonar and there are many new methods are provided recently. In this paper we study a beamformer by using a nesting line array and describe the implement on DSP. The method by using a nesting line array includes some steps: we divide the whole frequency range to some octaves by multiple and construct two symmetrical line arrays according the low and high frequency at every octave, The space between the sensors of the longer array is the twice of the other. Then two array outputs respectively pass through a compensation filter and get added together. Then the octave outputs respectively pass through a band pass filter which can get rid of the signal except this octave and get added all together to obtain the signal with constant beam shape over all the octaves. The signal processing should be implemented on a digital platform. We have solved some important problems in the implement by some efficient methods, (1) Linear interline can delay the discrete digital signal with a little time exactly and solves the problem of the inaccurate delay of digital signal at focus processing. (2) The band of the band-pass-filter is too small and the designing the filter is difficult. Getting the sampling frequency of the signal down can solves this problem. (3) To design a FIR filter according to the analog filter's frequency response can solve the problem of the analog filter can't be used directly to deal with the digital signal. (4) A FIR filter can produce a fixed delay to the input signal and the outputs of octave can't be added together for different time delays. We can delay the output of each octave by dots. The magnitude of the calculation of the implementation on digital platform is very large. The DSP calculating board has the advantage of processing multitasks at a time. We take use of the DSP board to improve the whole calculating speed and design the program on DSP according to the structure of the nesting line array method. It is proved by experimental results that the calculating speed on DSP can meet the real-time speed.
语种	中文
公开日期	2011-05-07
页码	42
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/976]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	方华. 数字平台上实现甚宽频带恒定束宽方法[D]. 中国科学院声学研究所. 中国科学院声学研究所. 2005.

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