The Study Of The Distribution Of Leaky Cable's Electromagnetic On Several Medium

The perimeter intruder location detecting system based on leaky cable is a newly invented outdoor detecting system in the recent years. It is applied to be on guard for broad area and complicated terrain, and it has some special characteristic such as high conceal property, the low error rate and so on. The perimeter intruder location detecting system makes use of leaky coaxial cable because it not only transmits the signal but also can emit and accept the signal. When somebody leaps over the leaky cable that is working, the variation of the electromagnetic signal can be detected, so it can give an alarm. In the world there are many scholars that studied the distribution of the electromagnetic of the leaky cable, but these researches are dead against the design of the leaky cable and its appliance in communication system, but the research that aims the leaky cable applying in the perimeter intruder location detecting system hasn't been covered.This paper is directed against SLYWV-75-10 type leaky cable which is applied to the perimeter intruder location detecting system. At first, we use finite-difference time-domain method (FDTD) to analyse the distribution of the electromagnetic of the leaky cable, then use the software XFDTD to emulate the distribution, finally, obtain the distribution picture of the leaky cable in three different medium. In addition, in two different medium, we detect the distribution of both the axial and the vertical direction, protract several curves by the data that measured. These curves are called the distribution curve of the leaky cable. In the end, we compare the result of the measure with that of the emulation, and get the result as follows:(1)In the near-field, the eradiate electric field of the leaky cable has the character of direction. In the far-field, the intensity of the electric field goes equality in circle direction;(2)The medium's relative permittivity directly affects attenuation degree of the leaky cable's radiation. The bigger the relative permittivity is, the quicker the attenuation of the radiation signal is and the shorter the distance of the transmission in radial direction the distribution assumes exponential attenuation and in axis direction the distribution assumes linear attenuation.(3)When radiant intensity is 50dBμV, measure the distribution of the electromagnetism in two medium (atmosphere and soil). The result is, in the vertical direction, the intensity of the electric field attenuates to nearly zero which is apart about 6m from the cable; in axis direction, because of the difference of the medium's relative permittivity, the biggest alertness of the leaky cable is different too, in the atmosphere about 90m,in the soil about 12m.(4)Comparing the result of the measure and the simulation, we can get the outcoming: the distribution of the electromagnetic of the leaky cable in medium that are referred to is inosculated basically.This paper has an important directive sense for the leaky cable'collocation and appliance in the outdoor detecting system.