【摘要】：對(duì)流層大氣高度一般在17千米以內(nèi),大多數(shù)電磁波傳播現(xiàn)象都在對(duì)流層中進(jìn)行。對(duì)流層大氣對(duì)電磁波傳播的影響是多方面的,其中包括對(duì)電磁波的散射、折射、繞射等傳播效應(yīng)。對(duì)流層大氣環(huán)境條件下所形成的波導(dǎo)是一種異常的大氣結(jié)構(gòu),它的出現(xiàn)成為影響電磁波在對(duì)流層中傳播的主要因素。這對(duì)艦船上以及海岸運(yùn)作的雷達(dá)、通信設(shè)備等都有很大影響。我國四大領(lǐng)海以及東南沿海都處在對(duì)流層波導(dǎo)高發(fā)地區(qū),因此開展對(duì)流層大氣波導(dǎo)環(huán)境下電磁波傳播特性研究具有實(shí)際的通信應(yīng)用價(jià)值和國防意義。本文首先介紹蒸發(fā)波導(dǎo)、無基礎(chǔ)層表面波導(dǎo)、有基礎(chǔ)層表面波導(dǎo)、懸空波導(dǎo)、混合型波導(dǎo)等的形成條件、折射率剖面模型以及分布區(qū)域。其次,從赫姆霍茲波動(dòng)方程開始,逐步推導(dǎo)出窄角拋物型方程。然后,使用分步傅里葉算法求解拋物型方程,分別得到標(biāo)準(zhǔn)大氣以及上述五種波導(dǎo)結(jié)構(gòu)下的電磁波傳播損耗分布情況。文章還分析大氣壓強(qiáng),溫度,相對(duì)濕度對(duì)大氣折射率梯度的影響以及海水介電常數(shù),天線高度等對(duì)電磁波傳播損耗的影響。結(jié)果表明,空氣的相對(duì)濕度對(duì)大氣折射指數(shù)影響最大;海水介電常數(shù)對(duì)電磁波傳播損耗影響較小,可以忽略不計(jì)。文章對(duì)窄角拋物型方程推導(dǎo)以及求解過程中引入的主要誤差進(jìn)行分析,建立偽微分算子引入誤差隨傳播仰角與折射指數(shù)變化的關(guān)系式,定量分析相對(duì)誤差隨上述因子變化的關(guān)系。進(jìn)一步從分離指數(shù)項(xiàng)所帶來誤差入手,兼顧計(jì)算精度,給出了計(jì)算步長與頻率的關(guān)系,由此可以在一定誤差范圍內(nèi),最大限度的增加計(jì)算步長,從而減少計(jì)算量,提高計(jì)算效率,這對(duì)嵌入拋物型方程算法系統(tǒng)的實(shí)時(shí)性具有重要意義。
[Abstract]:The tropospheric atmosphere is usually within 17 km, and most of the electromagnetic wave propagation takes place in the troposphere. The influence of tropospheric atmosphere on electromagnetic wave propagation is multifaceted, including scattering, refraction, diffraction and other propagation effects. The waveguide formed in the tropospheric atmosphere is an abnormal atmospheric structure, and its appearance becomes the main factor affecting the propagation of electromagnetic wave in the troposphere. This has a great impact on radar and communication equipment on ships and on the coast. The four major territorial seas and the southeast coast of China are all in the high incidence areas of tropospheric waveguides. Therefore, the study on the propagation characteristics of electromagnetic waves in tropospheric atmospheric waveguides has practical application value and national defense significance. In this paper, the formation conditions, refractive index profile model and distribution region of evaporation waveguide, non-base layer surface waveguide, suspended waveguide and hybrid waveguide are introduced. Secondly, starting with Hermholtz wave equation, the narrow angle parabolic equation is derived step by step. Then, the parabola equation is solved by using the split-step Fourier algorithm, and the electromagnetic wave propagation loss distribution in the standard atmosphere and the above five waveguide structures is obtained respectively. The effects of atmospheric pressure, temperature and relative humidity on the refractive index gradient of the atmosphere, and the effects of sea water dielectric constant and antenna height on the propagation loss of electromagnetic waves are also analyzed. The results show that the relative humidity of air has the greatest influence on the refractive index of the atmosphere, and the dielectric constant of seawater has little effect on the propagation loss of electromagnetic wave, which can be ignored. In this paper, the derivation of narrow angle parabola equation and the main errors introduced in the process of solving it are analyzed, and the relationship between the error introduced by pseudo differential operator and the variation of propagation elevation angle and refractive index is established. Quantitative analysis of the relationship between relative error and the above factors. Furthermore, starting with the error caused by the separation index term and taking into account the calculation accuracy, the relationship between the calculation step size and the frequency is given, so that the calculation step size can be increased to the greatest extent in a certain error range, thus reducing the amount of calculation. It is of great significance to improve the computational efficiency for the real-time performance of embedded parabola equation algorithm system.
【學(xué)位授予單位】：鄭州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN011.3

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本文編號(hào)：2475556