Research Of Sonar Pulse Detection And Passive Ranging

It is very dangerous for submarine when ranging by active SONAR transmitting pulse because active SONAR provides signal to enemy which will reveal itself and it is a tremendous disadvantage for submarine. Therefore, how to use passive SONAR to check signal and estimate the parameters of aim become a active theme in the underwater acoustic domain. The purpose of this thesis is to reserch and design a digital fish torpedo SONAR pulse detect system(DSPDS), to solve some defect which exist in traditional SONAR, to accomplish real-time detect the aim and judge the aim's type and estimate the center frequency, angle, dsintance, repeat period of target, to follow the fast moving target, as well as to adapt the system to different flank three sub-array types without the limitation of installation place.Commonly, in passive ranging SONAR, target range finding is accomplished by estimating the time delay between signals emanating from a remote source and received by three spatially separated array elements. With the help of passive ranging and bearing formula, which is derived for arbitrary linear array type, general characteristic of the time delay is analyzed in detail in the thesis. To higher the ranging accuracy, a bigger array aperture is required to effectively estimate the range of target far away. In addition, singnal processing measures are also indispensable, which leads to different time delay estimation (TDE) methods acceptable for far and near target status. For far targets, based on azimuth word from tracking system, K parameter distribution method (K-PDM) is used to estimate the time delay because of the lower signal to noise ratio (SNR) and the vague correlation summit. However, for near targets, K-CDM has the problem of range blurring, then direct measurement method (DMM) is used instead the higher SNR and the clear summit. The problem of whole course ranging is accomplished by switching these two methods appropriately.Though simple the passive ranging model in theory, the practical implementation detail is very complex because the time delay needed is of the order of micro-second, which is the same or less than the propagation time...