Gunshot Location Technology Based On Cross-spectrum Phase Fitting

In modern war and non-war military operations,snipers become ghosts of the battlefield with their concealment,flexibility and huge point killing ability,giving their opponents lethal killing and strong psychological deterrent effect on important targets.Therefore,the anti-sniper detection system is very significant to ensure the safety of military and civilian life.In this paper,based on the acoustic positioning of sniper rifle and using the microphone array time delay estimation positioning technology,the cross spectrum is filtered in frequency domain and the phase of the cross spectrum is fitted by the least square straight line method,in order to improve the accuracy of the spatial positioning of gunfire.The main work is as follows:1.The spatial model of microphone array is analyzed,including far-field model and near-field model.The definition of cross correlation,the evolution process of basic cross correlation and generalized cross correlation are introduced,combining the PHAT(Phase Transform)and SCOT(Smooth Coherence Transform)weighting,a PHAT/SCOT joint weighting algorithm with stronger anti-noise capability is proposed.2.For fractional order time delay estimation,the commonly used time domain linear interpolation,polynomial fitting algorithm and the corresponding least square principle are introduced.According to the linear relationship between cross spectrum phase and frequency of two signals,a time delay estimation algorithm based on cross spectrum phase fitting is proposed.3.The spatial regular tetrahedron array model is designed,and the overall time delay is comprehensively obtained according to the steps of first integer and then fraction.The key point is to use the cross spectrum phase fitting algorithm,to filter the cross spectrum in frequency domain to obtain low-frequency useful signals,and to use the least square straight line fitting method for the cross spectrum phase to obtain more accurate fractional time delay values.Then the gunfire was accurately oriented by geometric positioning method.Finally,the more accurate distance precision is obtained within the distance coordinate corrected by double array coordination.The simulation data show that when the gun is about 500 meters from the center of the array,the two-array interspectral phase fitting algorithm is positioned.Among them,the distance average error is 1.11 meters,the azimuth average error is 0.01 degrees,and the angle of pitch average error is 0.02 degrees.