Research On Underwater Target Multi-physical Field Coupling Detection Method

Human beings’perception of ocean information has long depended on a single physical field.With the development of sensor and signal detection technology,the detection of multiple physical fields has been paid more and more attention by various countries.This method combines the advantages of various physical field detection and makes up for the disadvantages of traditional single physical field detection limited by the development of sensors.This paper studies the electromagnetic coupling detection technology from principle to system design,and designs an electromagnetic coupling detection system based on the combined probe of coil and Tunnel Magneto Resistance（TMR）sensor.Obtaining the layout mode that makes the sensitive direction of the sensor perpendicular to the axial direction of the coil,which can reduce the primary field signal received by the sensor and ensure that the sensor works in the linear region,in order to improve the detection capability of the system.Through the derivation of the formula,it is concluded that the maximum amplitude of abnormal signal is detected when the radial distance between the target and the coil center sensor is=/2.The length diameter ratio,size and turns of rectangular coil are optimized.Phase sensitive detection algorithm and common mode noise suppression algorithm are used to realize the separation and noise suppression of primary field signal and secondary field signal.It is found that the designed detection system is not affected by the distributed capacitance between coil and water.It has ideal detection ability for targets in air and water.Different from the traditional double coil probe,which can only detect targets under coil,the probe designed in this paper can detect the coil side target,and the detection range is larger.This paper also makes a theoretical and simulation study on the new mechanism of acoustic magnetic coupling detection.It is obtained that the monopole sound source located100m below the sea surface with the sound source intensity of 200Pa emits 5Hz sound waves in the sea area of 506)8)×16)8),which can generate 10^-16T magnetic field signals 100m above the sea surface and 10^-15T magnetic field signals 100m below the sea surface.With the development of magnetic sensors,the detection of this magnitude of magnetic field is gradually feasible.