Wireless Transmission Technology Of Penetration Data In Deep-Buried Environment

In the modern battlefield,important military facilities and high-value equipment are buried deeply or reinforced with protective structures to improve their survivability,which makes it difficult for conventional ammunition to strike effectively.In order to destroy these important objects,ammunition is required to have considerable penetration capability.However,in the development process of penetration ammunition,it is difficult to recover the penetration data in the test,especially for conventional penetration ammunition,which has small diameter,limited internal space,short flight distance and short time in the test process.The commonly used soft/hard recovery method is inefficient and unreliable.The wireless transmission recovery method has the advantages of simple and convenient data recovery,good real-time performance,low cost,no need to install other equipment and recover the projectile,but it is limited by two points:one is the strong transmission attenuation of high-frequency wave in the penetration medium,the other is the large size of medium and low-frequency wave antenna,which can not be placed on conventional ammunition.In order to solve this problem,this paper will study on the wireless transmission technology of penetration data in deep buried environment.Firstly,the propagation characteristics of electromagnetic wave in deep buried environment are studied theoretically.Based on Maxwell equations,the wave equation,propagation characteristic equation,maximum propagation distance equation,reflection and transmission direction and energy equation are derived.Secondly,taking the propagation of uniform plane wave in uniform lossy medium as a model,the attenuation of electromagnetic wave with different frequencies in lossy medium,the influence of environmental conductivity on the propagation attenuation of electromagnetic wave and the propagation characteristic curve of electric and magnetic components in deep buried environment are analyzed by numerical simulation.According to the transmission equation,four optimization schemes are proposed to increase the transmission distance,which are to increase the output power of the transmitting module,to radiate relatively low frequency electromagnetic wave,to design a suitable missile antenna,and to combine wireless transmission with wire transmission.At the same time,the penetration ability of 433MHz and 2.4GHz electromagnetic wave is compared in the field deep burial test.Combined with the results of numerical analysis,the necessity of using lower frequency electromagnetic wave is further clarified.Thirdly,a new idea of antenna design flow is put forward,that is,first determine the type and physical size of antenna according to special conditions,and then carry out miniaturization(frequency reduction).In this paper,a circular microstrip antenna which can be conformable with the interior of the projectile is selected.The maximum diameter of the antenna is only 65mm(the diameter of the dielectric substrate and the floor).The antenna can be placed in the 75mm cavity of the 105mm projectile of the conventional ammunition.Then,by filling the dielectric substrate of the circular microstrip antenna with the magnetic negative super structure material,the frequency of the antenna is reduced.MWS in CST is used to model and simulate the designed antenna.The simulation results show that the antenna can radiate electromagnetic wave at low frequency 432MHz,and the electric dimension of patch radius(12.5mm)is only about λ_o/40,and the antenna can radiate electromagnetic wave normally at its resonance frequency of 2.3GHz.It is shown that the designed antenna can not only radiate 432MHz electromagnetic wave,but also realize dual band operation on the premise of satisfying the size.Finally,the simulation test of the antenna and the metal cavity is carried out,and the change of the far-field radiation performance of the antenna in different positions is obtained.