The Signal Processing Software Design Of Underwater High-speed Target's Trace Measuring System

Underwater high-speed target measuring system is used to locate the high-speed underwater target. The receiving array composed of four acoustic buoys, and they send the processed data to the control and display unit by wireless. And the control and display unit compute the track of the target and display it. The system has active and passive operating mode, and the dissertation mainly deals with the underwater acoustic signal processing software design under active operating mode.Under the active mode, the synergic target transmits two kinds of signal, one is Continuous Wave (CW) pulse, and the other is Linear Frequency Modulation (LFM) pulse. The buoys play important roles in detecting the type of the signal and estimating the arriving time, and then send the data to the central unit.The adaptive filter was used to deal with CW pulse. The receiving signal was processed by the filter first, and the output was used to detect CW pulse by both the length of envelop and the standard deviation of the instantaneous frequency. If there is a CW pulse, the arriving time and the frequency of CW can be obtained. To the LFM pulse, the copy correlator was used to estimate the arriving time of the LFM.The correlators were applied in receiving signals at first, and then in searching the peak of the output to estimate the time. In order to reduce the influence of Doppler Effect on the replica correlators, the frequency of CW was used to get the referenced signal of the correlators. The principle of signal processing and the idea of the software design is discussed systemically in the dissertation.The data processing system in the acoustic buoy employs two pieces of TMS320VC5509A fixed-point DSP. The mixing program was designed by C language and assembly language, and the effective correlation in DSP program is realized by assembly language. A fast algorithm was studied to detect the LFM signal in the outputs of the multi-correlator, which can restrain the jam between the channels. Moreover, the float-point data type and its function were defined, and the experiment result has shown they can avoid the overflow, increase the precision and decrease the computing time.The system was used in the SongHua Lake trial, and the result show the system can operate well.