The LOFAR And DEMON Analysis Of The Target's Through Characteristic

All kinds of ship targets have their own noise characteristics, which can be used for targets identification, classification, condition monitoring and so on. The noise abnormality of ship could make the ship become the target, which is easily destroyed by the underwater weapon, such as mine and torpedo. In order to reduce the risk of being destroyed and enhance the safety control, it is necessary to weaken the noise characteristics of ship target effectively timely, and it has extremely important military and economic value. Monitoring the daily condition of ship is the base for ship maintenance.This paper use haven monitoring as the application background, consider the frequency-domain characteristics of target noise, analysis the target characteristics with the combination of CABF(Conventional Array Beam-forming) processing and LOFAR analysis, DEMON analysis, and demonstrate the performance of the above mentioned methods with real data. Beam forming can enhance the signal-to-noises rate (SNR) of the signals, and give the target azimuth estimations; LOFAR analysis can show the nonstationarity of signal, and extract the distribution characteristics of broad-band strong line-spectrums; while DEMON analysis can get the low frequency modulated strong line-spectrums, and remedy the deficiency of LOFAR analysis in low frequency.In the paper, the basic theoretics of target's through characteristic is generalized firstly, then the basic principle and concrete implementation methods of CABF(Conventional Array Beam-forming), LOFAR analysis and DEMON analysis are discussed. Further more, the simulation research is made for CABF, LOFAR analysis and DEMON analysis in different SNR conditions, then the temporal-domain and frequency-domain characteristics between the signals of single hydrophone and the beam output are contrasted and analyzed. Then the LOFAR method of beam output and the DEMON method of multi-hydrophone information fusion are built to improve the comparable feature of the target's through characteristics. Finally, large numbers of ship noise data processing and analyzing are used to prove the validity, robustness and practicability of the CABF, LOFAR analysis and DEMON analysis methods.