New method for the efficient summation of double infinite series arising from the spectral domain analysis of frequency selective surfaces

When the method of moments (MoM) in the spectral domain is applied to the analysis of frequency selective surfaces, the entries of the MoM matrix are slowly convergent double infinite series. In this paper, a two-step acceleration technique is developed which makes it possible the fast and accurate computation of these double series in the particular case where subsectional rooftops are used as basis functions. The technique is based on a combination of the use of Kummer's transformation, the use of Poisson's transformation, and the determination of judicious Chebyshev polynomial interpolations of some of the spectral discrete functions involved in the infinite series. The results obtained show that when all the double series of the MoM matrix are to be computed with an accuracy of three significant figures, the new acceleration technique turns out to be about one thousand times faster than brute-force computation, and a few times faster than the acceleration technique based on fast Fourier transform.     

A circuital approach to evaluating the electromagnetic field on rectangular apertures backed by rectangular cavities

In this paper, the problem of evaluating the electromagnetic field on rectangular apertures backed by rectangular cavities is investigated. The electromagnetic-field distribution is derived by using a circuital model of an aperture and suitable forcing terms introduced into the equations related to the aperture model. The effects of a rectangular cavity on the aperture-field distribution are assessed by considering the rectangular cavity as a load impedance. The impedance value is obtained by modeling the rectangular cavity as a length of rectangular waveguide back-ended by a short. The distribution of the electromagnetic field on the aperture is used as an exciting source to evaluate, through a modal expansion, the electromagnetic field inside the cavity. Numerical simulations are in a good agreement with both other theoretical models and experimental data.     

On the electromagnetic scattering from infinite rectangular grids with finite conductivity

-The development of a new numerical technique for the analysis of electromagnetic scattering from a rectangular wire (or strip) mesh. According to this technique the conjugate gradient method (CGM) and the fast Fourier transform (FFT) are used to solved for the aperture fields and the induced current densities. The method is efficient because 1) it makes use of the fast Fourier transform, 2) it converts a set of integrodifferential equations into a set of algebraic equations, and 3) it does not require inversion of any matrices. Unlike the moment method, the spectral iteration approach (SIT), and the averaged boundary conditions method, this technique can be used for arbitrary size and spacing between adjacent strips. The equivalent radius principle is used to determine the reflection coefficient from a wire mesh. Results, examples, and comparisons of this method with other methods support the validity of the algorithm.     

Shielding effectiveness of apertures in rectangular cavities

The shielding effectiveness of a rectangular cavity with an aperture in near-field conditions is calculated by means of the methods of moments. Theoretical results are compared to experimental values with good agreement     

On the use of Chebyschev-Toeplitz algorithm in accelerating thenumerical convergence of infinite series

It is shown that a simple application of the Chebyschev-Toeplitz algorithm enhances the rate of convergence of slowly converging series. The algorithm is applied to series representing the periodic Green's functions involving a single infinite summation. The algorithm yields highly accurate results within relatively fewer terms. A quantitative comparison is shown with methods previously reported in the literature     

On the double injection negative-resistance in magnetic field

By using the regional approximation, the double injection negative resistance in a magnetic field was studied. The results obtained show that in a magnetic field a sample length less than a critical length, L_cr, produces a decreasing of the voltage range of the negative resistance region, while a sample length greater than L_cr produces, under certain conditions, an opposite effect. This situation is related to the domination of the diffusion and drift effects, respectively.     

High-frequency RCS of open cavities with rectangular and circularcross sections

The radar cross-section (RCS) analysis of open-ended cavities with rectangular and circular cross sections is carried out using the waveguide modal approach and the shooting-and-bouncing ray (SBR) approach. For a cavity opening on the order of ten wavelengths or larger, the comparison between the two approaches is excellent. It is also observed that at lower frequencies the SBR results deviate from the more accurate modal results. On the other hand, the SBR approach allows for greater flexibility in geometrical modeling, and can be applied to problems where waveguide modes cannot be easily found. SBR results for an offset rectangular cavity and a circular cavity with rounded endplate are presented     

Analysis of dielectric covered infinite array of rectangular microstrip antennas

A method is presented to determine the active input impedance of an infinite array of rectangular patches embedded in a dielectric layer. The reaction integral equation is used to include details of feed structure into the formulation. The matching performance over wide scan angles of the printed antenna with a dielectric cover is studied. The results obtained by the present method are compared with the theoretical and experimental results reported earlier, for an array without a cover layer.     

Complete electric field of the infinite slot antenna

The complete electric field of an aperture, with uniform excitation, in an infinite plane is derived and studied.     

Aperture matching for an infinite circular polarized array of rectangular waveguides

This paper studies the polarization of the main beam radiated from an infinite array of rectangular waveguides, and in particular, illustrates the matching procedure for the design of a circularly polarized array. It is demonstrated that the use of resonant irises at the waveguide openings together with a conventional matching junction inside the waveguides can improve both the power and the axial ratio of the main beam in a circularly polarized array. In general, a good matching design is the one which gives a proper compromise between the power and the polarization, and is not necessarily the one minimizing the reflection.     

基于磁通元电场叠加法的涡旋电场计算

提出用磁通元电场叠加法求解涡旋电场,利用该方法推导出了空间旋转平面区域产生的涡旋电场的时域表达式,验证了磁通元电场叠加法求解涡旋电场的正确性。     

Electromagnetic field of an infinite helical sheath

The relevant fields of an infinite helical sheath, produced by a current distribution on the helical surface, are obtained for the case in which the internal medium is different from the external one.     

On the electromagnetic field of a rectangular patch of uniform andlinear distributions of current in the source region

Exact analytical expressions for the magnetic vector potential and the electric and magnetic fields of a rectangular patch of uniform and linear distributions of electric current in an unbounded homogeneous medium have been given by the authors in a previous paper (see ibid., vol.37, p.1503-9, December 1989). In this paper, these expressions are utilized to investigate the nature of the electromagnetic field of such current distributions in the source region. Specifically, the singular parts and points of singularity of the various functions involved in the analytical expressions, as well as those of the field components of both current distributions, are obtained and tabulated     

Analysis of an infinite array of rectangular microstrip patches with idealized probe feeds

A solution is presented for the problem of an infinite array of microstrip patches fed with short current elements. The input reflection coefficient is calculated versus scan angle in an arbitrary scan plane, and the effects of substrate parameters and grid spacings are considered. The scan blindness phenomenom is observed and discussed in terms of a forced surface wave response. Measurements from waveguide simulators confirm the theory for thin substrates.     

Numerical solutions for an infinite phased array of rectangular waveguides with thick walls

A numerical analysis of an infinite phased array of open rectangular waveguides has been made which includes the effects of wall thickness. Two planes of scan, theHand quasi-Eplanes, have been considered. In these cases, the general vector problem can be expressed in the form of a scalar one-dimensional Fredholm integral equation of the first kind. The approximate fields obtained numerically from the integral equation are used for the evaluation of the input complex reflection coefficient. A variational expression for the reflection coefficient is developed and used for improving the accuracy. Numerical results for theHand quasi-Eplane scans are presented as a function of wall thickness and scan angle. Agreement with experimental results is very good.     

On the number of rectangular tilings.

Adaptive multiscale representations via quadtree splitting and two-dimensional (2-D) wavelet packets, which amount to space and frequency decompositions, respectively, are powerful concepts that have been widely used in applications. These schemes are direct extensions of their one-dimensional counterparts, in particular, by coupling of the two dimensions and restricting to only one possible further partition of each block into four subblocks. In this paper, we consider more flexible schemes that exploit more variations of multidimensional data structure. In the meantime, we restrict to tree-based decompositions that are amenable to fast algorithms and have low indexing cost. Examples of these decomposition schemes are anisotropic wavelet packets, dyadic rectangular tilings, separate dimension decompositions, and general rectangular tilings. We compute the numbers of possible decompositions for each of these schemes. We also give bounds for some of these numbers. These results show that the new rectangular tiling schemes lead to much larger sets of 2-D space and frequency decompositions than the commonly-used quadtree-based schemes, therefore bearing the potential to obtain better representation for a given image.     

Integrated tunable optofluidics filter based on the plasmonic structure with double side-coupled cavities

A novel method is presented to enhance the resonant transmission contrast ratio in metal-insulator-metal（MIM）sidecoupled-cavity waveguide.The finite difference time domain（FDTD）method is used to simulate and study the optical properties of the filter based on double side-coupled cavities structure with optofluidics pump system（OPS）.This system provides a flexible way to change wavelength in the optical filter.In the numerical simulation,the resonant wavelengths from 1000 nm to 1550 nm are analyzed.We find that the double side-coupled cavities structure with OPS has higher onresonance transmittance and better wavelength selectivity than the single side-coupled cavity structure with OPS.     

RCS analysis of canonical,two-dimensional material-loaded cavities with rectangular and circular cross sections

A rigorous radar cross section (rcs) analysis of canonical, two-dimensional material-loaded cavities with rectangular and circular cross sections is carried out using the Wiener-Hopf technique and the Riemann-Hilbert problem technique, respectively. Both E and H polarizations are treated. It is shown via numerical examples that the absorbing layer loading inside the cavities gives rise to the significant rcs reduction. The results can be used as a reference solution for validating more general-purpose computer codes based on approximate methods.     

填充旋波媒质矩形波导电磁场的解析求解

提出了一种获得填充旋波媒质矩形波导电磁场解析解的新方法.从旋波媒质本构方程和麦克斯韦方程出发,讨论了电磁波在旋波媒质中的传播特性.经过矢量变换,将难以解析求解的波动方程化简为常规的波动方程,并对其进行了求解.利用矢量变换关系和场矢量的边界条件,求得了电磁场分量表达式和求解传播常数的特征方程组.