Research On The Key Technology Of Infrasound Focusing Method Based On Three Dimensional Phased Array

Infrasound wave can realize the long distance transmission in the medium which depend on its physical characteristics,in the meantime infrasound wave spread in the form of radiation.So infrasound does not have any directionality when it travels in the atmosphere.Aiming at infrasonic orientation,a new method of three dimensional phased arrays is proposed to achieve infrasound orientation.The main research work includes the following aspects:(1)Theoretical study on direction of three dimensional array phased array.According to the directed product theorem and the directional analysis method of phased array to deduce the formula of direction function,the formula of main lobe width and the calculation formula of delay time of each array element is deduced,laying foundation for simulation research of infrasonic direction.(2)Simulation and analysis of three dimensional array infrasonic direction:The direction function formula and main lobe width formula are simulated based on the three dimensional phased array.The influence of infrasound direction according to the array form,array element form,array element spacing,array element number and infrasonic frequency is studied.The image of infrasound direction on three dimensional phased arrays and two dimensional phased arrays when they have the same element number is contrasted.Direction effect influence caused by changing of array form and Z axis element spacing is analyzed.(3)Design of three dimensional phased array delay circuit:FPGA digital circuit to design delay circuit of three-dimensional array and delay trigger elements using high frequency clock signal of FPGA base on counter delay method are adopted.And the PLL module in the FPGA chip is used,doubling the clock signal frequency to realize the design of the high precision delay system.Finally,a desired delayed triggering signal through experiment of the delay circuit is obtained.And the deviation of actual trigger signal is analyzed.Through the research of the infrasound direction effect under the three dimensional array form and influence of infrasound direction effect when three-dimensional array parameters change,not only the 3D directional phased array phased array focusing for infrasound directional is proved feasibility,but also the directional effect is better than the traditional phased array.