本文選題：電磁泄漏　切入點(diǎn)：電磁屏蔽　出處：《華北電力大學(xué)》2015年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：電磁屏蔽是通過(guò)場(chǎng)耦合途徑抑制電磁干擾的主要技術(shù)。它的實(shí)現(xiàn)可通過(guò)使用一個(gè)金屬外殼包圍干擾源,以降低其場(chǎng)泄漏,或減少外部磁場(chǎng)強(qiáng)度來(lái)篩選敏感對(duì)象。雖然一個(gè)封閉的金屬外殼對(duì)于電磁波具有非常高的屏蔽效能SE,但是因?yàn)橐恍⿲?shí)際功能,外殼上不可避免的會(huì)出現(xiàn)小孔,小孔的存在會(huì)導(dǎo)致SE顯著減少。通常,在用于SE測(cè)量的標(biāo)準(zhǔn)方法中,一個(gè)屏蔽外殼的SE被定義為沒(méi)有外殼時(shí)給定點(diǎn)的場(chǎng)強(qiáng)與外殼存在時(shí)該點(diǎn)的場(chǎng)強(qiáng)之比。其中,要求場(chǎng)源被放置在外殼外部。換句話(huà)說(shuō),場(chǎng)的觀察點(diǎn)是在外殼內(nèi)部,其優(yōu)點(diǎn)是減少了其他不必要的干擾源對(duì)所接收?qǐng)鰪?qiáng)的潛在影響。所以,在許多文獻(xiàn)中對(duì)于SE的評(píng)價(jià)都是對(duì)于外部場(chǎng)源。然而,相反的情況下,源在外殼內(nèi)部也具有實(shí)際意義,值得予以關(guān)注。原則上,這兩種情況可根據(jù)互易原理相互轉(zhuǎn)化。然而,由于對(duì)“外部源”實(shí)例尚未進(jìn)行全面和深入的研究,我們不能為每個(gè)“內(nèi)部源”實(shí)例找到合適的“對(duì)偶問(wèn)題”。例如,對(duì)于后者,在近場(chǎng)區(qū)域中的場(chǎng)分布是主要考慮的問(wèn)題,但是對(duì)于前者,激勵(lì)源(通常假設(shè)是平面波)在遠(yuǎn)場(chǎng)區(qū)定位明顯。本文首先基于模式展開(kāi)方法得到的解析公式,計(jì)算了電偶極子天線(xiàn)激勵(lì)下矩形屏蔽體的電磁場(chǎng)分布,獲得了屏蔽體內(nèi)壁和內(nèi)部的電場(chǎng)和磁場(chǎng)分布特性。接著,提出了一種用于計(jì)算開(kāi)孔矩形腔體電磁泄漏場(chǎng)的解析理論模型。該理論模型先基于模式展開(kāi)法求解封閉腔場(chǎng),進(jìn)而依據(jù)Bethe小孔耦合理論將泄漏場(chǎng)與封閉腔場(chǎng)用等效偶極子關(guān)聯(lián)。該模型可以考慮波頻率、場(chǎng)源位置、開(kāi)孔位置及場(chǎng)強(qiáng)觀測(cè)點(diǎn)位置等因素的影響,計(jì)算結(jié)果與全波仿真結(jié)果一致。最后,提出了一種用于計(jì)算封堵孔矩形腔體電磁泄漏的解析理論模型。該模型同樣先基于模式展開(kāi)法求解封閉腔場(chǎng),進(jìn)而用平面波垂直入射無(wú)限大導(dǎo)體的邊界條件近似計(jì)算出透射場(chǎng)的切向分量,最后通過(guò)面磁流在空間產(chǎn)生的電場(chǎng)求解出封堵孔的泄漏場(chǎng)分布。
[Abstract]:Electromagnetic shielding is the main technology to suppress electromagnetic interference through field coupling. It can be realized by using a metal shell to surround the interference source to reduce its field leakage. Or reduce the external magnetic field intensity to screen sensitive objects. Although a closed metal shell has a very high shielding efficiency for electromagnetic waves, because of some practical functions, there are inevitable small holes in the shell. The presence of small holes can result in a significant decrease in SE. Generally, in standard methods for SE measurement, SE of a shielded shell is defined as the ratio of the field strength given to a given point in the absence of a shell to the field strength of the point at which the shell exists. The field source is required to be placed outside the shell. In other words, the field's observation point is inside the shell, which has the advantage of reducing the potential impact of other unnecessary interference sources on the received field strength. In many literatures, the evaluation of SE is for external field sources. However, on the contrary, the source also has practical meaning inside the shell and deserves attention. In principle, the two cases can be converted to each other according to the reciprocity principle. Since there has not been a comprehensive and in-depth study of "external source" instances, we cannot find an appropriate "dual problem" for each "internal source" instance. For the latter, for example, the field distribution in the near-field region is the main consideration. But for the former, the excitation source (usually assumed to be a plane wave) is obviously located in the far field. Firstly, based on the analytical formula obtained by the mode expansion method, the electromagnetic field distribution of the rectangular shielding body excited by the electric dipole antenna is calculated. The distribution characteristics of electric field and magnetic field in the shielding wall and inside are obtained. Then, an analytical theoretical model for calculating electromagnetic leakage field of rectangular cavity with open hole is proposed. The theoretical model is based on the mode expansion method to solve the closed cavity field. Furthermore, the leakage field and the closed cavity field are correlated by equivalent dipole according to the Bethe small-hole coupling theory. The model can consider the influence of the wave frequency, the location of the field source, the location of the opening hole and the position of the observation point of the field strength, and so on. The calculated results are consistent with the full wave simulation results. Finally, an analytical theoretical model for calculating electromagnetic leakage of a rectangular cavity is proposed. The model is also based on the mode expansion method to solve the closed cavity field. Then the tangential component of the transmission field is approximately calculated by the boundary condition of the infinite conductor vertically incident by plane wave. Finally, the leakage field distribution of the sealing hole is solved by the electric field generated by the surface magnetic flow in the space.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TN03

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本文編號(hào)：1621595