Electromagnetic transmission through mesh covered apertures and arrays of apertures in a conducting screen

The problem of electromagnetic transmission through wire mesh covered arbitrarily shaped aperture or arrays of apertures (possibly covered by a thin lossy dielectric sheet) in a perfectly conducting ground plane is considered. The equivalence principle and image theory are used to derive an integral equation for the equivalent magnetic currents. The method of moments is utilized to solve the integral equation, with the aperture modeled by triangular patches. Numerical results are presented for transmission coefficients and transmission cross-section patterns for electrically small apertures.     

Electromagnetic penetration through apertures in conducting surfaces

In designing hardened systems, one must be able to characterize as well as quantitatively determine the penetration of EMP signals through apertures of general shapes in structures of varying configurations. In this paper a tutorial review of a number of methods for analyzing such aperture problems is presented with an emphasis on techniques. The discussion presented herein is reasonably self-contained and is supplemented by references to classical as well as current approaches to the aperture problem. An extensive set of representative numerical results is included.     

Electromagnetic coupling to a cable through apertures

Electromagnetic field penetration through apertures is investigated numerically and experimentally. The coupling to a cable located behind an aperture is determined in terms of the open circuit voltage of the cable. A square and a circular aperture are taken as examples, and the open circuit voltage is calculated and verified by an experiment. The apertures are modeled by employing Babinet's principle and solving the complementary flat plate problem using wire-grid modeling. Comparisons with radar cross section measurements were also made to verify the wire-grid modeling.     

Electromagnetic scattering from multiple rectangular apertures in athick conducting screen

Electromagnetic wave scattering from multiple rectangular apertures in a thick conducting screen is studied. The Fourier-transform and mode-matching technique are used to obtain simultaneous equations for the modal coefficients. The simultaneous equations are solved to represent the scattered and transmitted fields in series forms which are suitable for numerical computation. The numerical computations are performed to illustrate the aperture transmission and scattering behavior in terms of aperture size, incident angle, and frequency. The effects of the finite number of apertures on the transmission characteristics are discussed     

Electromagnetic transmission through multiple circular apertures in a thick conducting plane

The boundary-value problem of electromagnetic wave scattering from multiple circular apertures in a thick conducting plane is rigorously solved. The eigenfunction expansion, integral transform, and superposition principle are utilized to represent the scattered field in the discrete and continuous modes. The boundary conditions are enforced to obtain a set of simultaneous equations for the discrete modal coefficients. The transmission coefficient is represented in a fast convergent series. Computation is performed to illustrate the behavior of transmission and coupling through multiple circular apertures in terms of the aperture geometry.     

Mutual coupling between two small circular apertures in aconducting screen

With the use of the reaction integral and two-dimensional Fourier transform, an analytical expression for mutual coupling between two small circular apertures in a conducting screen, excited by a normally incident plane electromagnetic wave, is obtained. Numerical examples for two different polarizations of the plane wave are investigated. The expression for the mutual admittance gives a correct value of the self-admittance of a small aperture when the distance between the holes is equal to zero     

Electromagnetic excitation of a wire through an aperture-perforated conducting screen

Integro-differential equations are formulated for the general problem of a finite-length wire excited through an arbitrarily shaped aperture in a conducting screen. The wire is assumed to be electrically thin and perfectly conducting, and it is arbitrarily oriented behind the perfectly conducting screen of infinite extent. A known, specified incident field illuminates the perforated-screen/wire structure. The integro-differential equations fully account for the coupling between the wire and the aperture/screen. They are specialized to the case of the wire parallel to the screen with the aperture a narrow slot of general length. These special equations are solved numerically and data are presented for wire currents and aperture fields under selected conditions of wire/slot lengths and orientation. Data indicative of the coupling between the wire and slot are presented.     

无限大导体表面孔缝耦合电磁能量分析

为有效设计电子设备，有必要了解它的最坏电磁工作环境，知道有多少电磁场通过耦合进入系统。采用矩量法分析了任意平面波通过无限大平板上小孔耦合的电磁能量，计算了电磁波通过了小孔耦合能量传输系数。     

Electromagnetic coupling to an infinite wire through a slot in a conducting plane

The problem of electromagnetic coupling to a long wire behind a slot-perforated conducting plane is considered by the method of moments. An equivalent circuit is obtained for the transmission line mode of the wire-slot system. An interesting result of the analysis is that, when the wire is terminated in loads for maximum power transfer, orders of magnitude more power may be transferred through the slot when the wire is present than when the wire is absent.     

Electromagnetic coupling mechanism to a conducting strip through anarrow slit in a parallel-plate waveguide

The problem of electromagnetic coupling to a conducting strip through a narrow slit in a parallel-plate waveguide (PPW) is reconsidered with an emphasis on the radiative coupling mechanism. Two different types of coupling are discussed: cavity and parasitic. The maximum coupled power in both cases is observed to be almost the maximum available power from the slit (half of the incident power in the PPW), even though the two types of coupling are quite different from each other in their equivalent circuit representation or coupling mechanism. The similarity between the problem of cavity-type coupling and the previously reported transmission resonance problem through a narrow slit in thick screens is also described in connection with the aperture-body resonance phenomenon     

Electromagnetic penetration into a rectangular cavity with multiplerectangular apertures in a conducting plane

Electromagnetic wave penetration into a rectangular cavity with multiple rectangular apertures is studied. The Fourier transform and the mode matching method are used to obtain simultaneous equations for the modal coefficients. The simultaneous equations are solved to represent the cavity field in series forms, which are suitable for numerical computations. Numerical computations are performed to investigate the field penetration into a cavity in terms of the shielding effectiveness for a various geometry     

Electromagnetic transmission through apertures in a cavity in a thick conductor

The problem of electromagnetic coupling from one region to another through an aperture-to-cavity-to-aperture system is specialized to the case of electrically small circular apertures on the axis of a cylindrical cavity of circular cross section for the transverse electromagnetic (TEM) and transverse electric (TE) cases. A simple equivalent circuit for the coupling system is developed. It is found that for certain cavity depths an exceptionally large amount of electromagnetic energy can be transmitted, and that for identical apertures the transmission cross section of the system is independent of the common radius of the apertures as well as the radius of the cavity.     

Efficient power transfer through small apertures

Efficient power transfer through a small slot in a thin conducting screen separating two resonant cavities was experimentally achieved by empirically optimising the natural resonant frequency of the slot and the circuit coupling factors. The design of a power combining circuit based on the use of slot coupled microstrip sources is discussed in terms of an electrical equivalent circuit which confirms that a high power transfer efficiency is possible with such an arrangement.<>     

Electromagnetic transmission through narrow slots in thick conducting screens

The general formulas for electromagnetic transmission through an infinitely long slot in a perfectly conducting screen of finite thickness are specialized to the case of a narrow slot. The slot may be filled with a homogeneous isotropic material. A simple equivalent circuit for the narrow slot is developed. It is found that for certain screen thicknesses the slot becomes resonant, and exceptionally large transmission of energy may occur. In fact, as the slot width approaches zero, the transmission width at resonance becomes1/piwavelengths regardless of the actual slot width. The effect of loading the slot with a lossy dielectric is also considered. Computations are given to illustrate the validity of the equivalent circuit model and the accuracy of transmission characteristics computed from it.     

A mode-matching approach to determine the shielding properties of a doubly periodic array of rectangular apertures in a thick conducting screen

The application of the mode-matching technique to determine the shielding properties of a thick doubly periodic conducting screen of rectangular apertures is presented. Floquet waves are used to represent the reflected and transmitted fields, while waveguide modes are used to determine the fields within the screen. Expressions for all fields are formed using Hertzian potentials. After enforcing boundary conditions and forming a system of linear equations, the mode coefficients are determined using standard techniques. Numerical results show the effect of increasing thickness and incidence angle variation on transmitted power. It is shown that by selectively choosing the number of waveguide modes, meaningful results for transmission can be obtained for screens whose thickness is several times the size of the apertures. The results also demonstrate the relationship between this approach and application of the waveguide below cutoff principle. It is also noted that at higher frequencies, higher order Floquet modes will propagate and contribute to the transmitted power.     

Electromagnetic transmission through inhomogeneously filled slotsin a thick conducting plane-arbitrary incidence

The penetration of an arbitrarily incident electromagnetic wave through a slot filled with inhomogeneous material in a thick conducting plane is analyzed. The solution is obtained via a combined finite-element method/method of moments algorithm based on the generalized network formulation. The discretization of the generalized network formulation is performed via the method of moments. The finite-element method is then used to compute the fields within the inhomogeneous interior cavity region, leading to the construction of the interior aperture admittance matrix. It is shown that with the use of entire domain basis functions, the construction of the aperture admittance matrices is computationally efficient. Furthermore, this method is attractive since it preserves the sparsity of the finite-element method matrix, reducing computational memory requirements. Some examples of the penetration of inhomogeneously filled slots of various cross sections are presented     

电磁波对不规则地面上架空线的影响

对不规则金属地表面上有限长架空线受平面电磁波影响的问题提出了一个有效的解决方案 :采用复合矩量法求解不规则地表面对平面电磁波的散射 ,再针对具有分布源的架空通信传输线 ,采用解析与数值相结合的方法求解。详细地介绍了求解平面电磁波对不规则地面上架空线影响的理论分析和计算过程 ,并且针对实际工程应用的典型参数给出了计算实例并讨论了计算结果。该方案也适用于航行轮船及待发射飞行器表面上通信电缆的电磁干扰问题     

Electromagnetic pulse (EMP) penetration through circular apertures in the frequency domain

Equations and curves are given for estimating field coupling from a normally electromagnetic pulse (EMP) incident plane wave through a circular aperture within a thin planar surface.     

Electromagnetic scattering by and transmission through athree-dimensional slot in a thick conducting plane

A hybrid numerical technique for a characterization of the scattering and transmission properties of a three-dimensional slot in a thick conducting plane is presented. The technique combines the finite element and boundary integral methods to formulate a system for the solution of the aperture fields and by virtue of the finite element method, it is applicable to inhomogeneously filled slots of arbitrary shape. The numerical implementation is described for the edge-based expansion functions associated with rectangular brick elements, and examples are presented demonstrating the validity, versatility, and capability of the technique. These also provide some understanding of the slots scattering and transmission properties as a function of its geometry and material filling