| With the development of communication technology and the increasing demand of application,it puts a higher requirement for the quality of wireless communication in the confined space and narrow area,such as subway,tunnel,mine,high-speed rail and light rail,therefore,it also puts forward a higher requirement for the quality of radio coverage in these scenes.However,due to the multipath fading effect in the confined space,the radio wave is easy to interfere with the circumstance or is easily affected by the circumstance in this type of confined space,and it cannot attain the satisfied effect through the discrete antenna system,so it can achieve an efficient coverage of radio wave by using leaky coaxial cables or leaky waveguides in the confined space.However,there are several elements to influence the leaky waveguide's radiation characteristics in the actual application,for example,several discontinuous structures or circumstance may influence the distribution of electric field around the leaky waveguide,therefore,it is necessary to research the effect that may be caused by various discontinuous conditions.In this paper,aimed at this kind of demand of application,the influence on the radio wave coverage of leaky waveguide,produced by the flange between waveguides,accumulated snow in the environment,and the power difference on the both sides of the repeater amplifier,are mainly studied,and it can provide an important basis for the design and evaluation of the radio wave coverage of leaky waveguide in the confined space and narrow area.The main work and research results of this paper are as follows:1.When two leaky waveguides are connected through a flange,it will cause a discontinuous configuration and the effect on the distribution of the electric field is studied,and when the position of flange is shifted off the center of two adjacent slots,the effect on the distribution of the near field's uniformity is studied.According to the situation,the improvement measures are implied,and they are decreasing the height of flange above the leaky waveguide or cutting the flange with different angles to reduce the electromagnetic wave barrier caused by the flange,in the result,the stability of the electric field will be obtained.2.According to the empirical formulas,the dielectric constant of snow with different water content in volume is calculated in 2.4GHz,and when the accumulating snow above the leaky waveguide presents random distribution with discontinuous condition,the influence of snow on the near field of the leaky waveguide is studied,and the mechanism of the influence of snow on the field distribution is analyzed from two aspects of the circumferential distribution and the axial distribution along the waveguide.On the basis of analysis and research,the improvement measure of reducing the influence of the accumulating snow is implied,and a dielectric layer is inserted in between the accumulating snow and the leaky waveguide to weaken the ability of snow to absorb the energy directly.3.According to the equivalent principle of magnetic current source and the relationship between element and array factor of array antenna,the calculation formulas of the near field distribution of leaky waveguide is derived,and when the power is amplified with different multiples(100times,500times,1000times)suddenly,the influence of power discontinuity on coupling loss is studied,and the reason of this phenomenon is analyzed theoretically.In view of the above,the improvement measure is implied,and it is using the absorbing material to suppress the energy on the strong side within a certain distance to make the coupling loss achieve a smooth transition between the weak side of power and the strong side of power of the repeater amplifier. |
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