Research And Realization Of Passive Sonar's Simulator Signal Sorce

Active SONAR provides signal for enemy when ranging by transmitting pulse and this is very dangerous for submarine. Therefore, passive SONAR, aiming at universal noise targets, becomes the dominating SONAR of submarine. As we know, noise target ranging technology is one of its main problems. The purpose of this thesis is to study and design a digital self examination system, to simulate noise targets and plus targets for passive ranging system. This system can provides simulating signals in some areas for a three spatially separated array.In noise target passive ranging SONAR (NTPRS), 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, first of all, 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 (X-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 fluctuation of underwater channel. Consequently, some signal processing and real-time correction algorithm must be conceived for passive ranging. This thesis discussed the general design principle of simulating noise targets, include direct calculating, by approximately formula and by tables, and did some compared between them. In the project, we used the method of calculating by look up tables,...