Analysis of mutual coupling in finite arrays of different-sizedrectangular waveguides

A Green's function approach is used to analyze mutual coupling in a finite array of different-sized rectangular waveguides arranged on a rectangular grid. In calculating the self- and mutual admittances for mode coupling, a quadruple integration over the source and observer apertures is involved. Possible means of reducing the order of integration are discussed, with the change of variables approach of L. Lewin (1951) being selected. This approach is generalized to allow coupling between different-sized apertures and leads to derivation of mutual admittance expressions for all possible combinations of transverse electric (TE) and transverse magnetic (TM) mode coupling. Calculations using these expressions are shown to be in good agreement with results published earlier by R.J. Mailloux (1969) and measured data for an antenna comprising a square waveguide and two rectangular waveguides. Coupling between closely spaced different-sized square waveguides is also investigated, and for small apertures minimum coupling is shown to occur when the aperture sidelength is about 1.15 λ     

Mode Conversion in Tapered Waveguides At and Near Cutoff

The coupling coefficient between the TE/sub 11/ mode and the TM/sub 11/ mode in tapered circular waveguides is derived, and at cutoff frequency it tends to approach an infinity of the order of 0/sup -1/4/. It is surprising to discover that the corresponding coupling coefficient between the TE/sub 10/ mode and the TM/sub 12/ mode in tapered rectangular waveguides approaches instead a zero of the order of 0/sup 1/4/ at cutoff frequency. Accordingly, for the modes concerned, the choice of using circular or square waveguides as tapers for transition at and near cutoff frequency is significant in reducing mode conversion level. At and near cutoff frequency a "synthesized" square taper is better in that it is shorter than a "synthesized" circular taper for the same mode conversion levels. On the other hand, for frequencies far away from cutoff the choice is insignificant. Design procedures for "synthesized" waveguide tapers at and near cutoff are presented, and the results of measurements are in agreement with the theoretical calculations.     

TFT-LCD过孔接触电阻研究

研究了过孔接触电阻变化规律,并进行机理分析,为优化薄膜晶体管的过孔设计提供依据。首先,运用开尔文四线检测法对不同大小、形状、数量的钼/铝/钼结构的栅极和源/漏层金属与氧化铟锡连接过孔的接触电阻进行测试。然后,通过扫描电子显微镜、能量色散X射线光谱仪和聚焦离子束显微镜对过孔内部形貌进行表征。最后,对过孔接触电阻变化规律进行机理分析。实验结果表明:过孔面积越大,接触电阻越小;过孔面积相同时,长方形过孔的接触电阻小于正方形过孔的接触电阻,多小孔的接触电阻小于单大孔的接触电阻,栅极金属与氧化铟锡的过孔接触电阻小于源/漏层金属与氧化铟锡的过孔接触电阻。为了降低钼/铝/钼与氧化铟锡连接过孔的接触电阻,过孔面积尽可能最大化,采用长方形过孔优于正方形过孔,多小过孔优于单大孔设计,同时优化过孔刻蚀工艺,减少过孔内顶层钼的损失。     

Efficient and accurate evaluation of external mutual couplingbetween compound broad wall slots

The efficient and accurate evaluation of external mutual coupling between compound broad-wall slots cut in rectangular waveguides is addressed. The special case of longitudinal slots is also considered. Errors introduced by approximations used in some mutual coupling expressions are investigated and numerical results are presented for a range of waveguide and slot parameters. It is shown that for most applications, mutual coupling expressions can be determined in terms of single numerical integrals     

An integral equation analysis of an infinite array of rectangulardielectric waveguides

An integral equation analysis is applied to the study of the propagation characteristics of an infinite array of dielectric waveguides. The geometry under study is assumed to be rectangular. To find the Green's function of the structure, the Floquet theorem is applied such that the mutual coupling between dielectric waveguide elements is effectively included in the analysis. The effect of the coupling on the propagation characteristics of a dielectric waveguide is studied by varying the size of the Floquet cell. The validity of this analysis to simulate the case of an open dielectric waveguide is confirmed by a comparison with previous results, this in spite of the fact that radiation and leaky wave modes are not accounted for. The complex modes due to the periodicity of the structure are found and their properties are described. The analysis presented, with minor modification, can deal with the problems of dielectric image lines, or dielectric-loaded metallic waveguides     

Equivalent circuit parameters of an aperture coupled open resonatorcavity

In this paper, we use modified form of Bethe's small hole coupling theory to compute equivalent circuit parameters of an aperture coupled open resonator cavity. The open resonator cavity is composed of spherical mirrors of circular cross section. The cavity is coupled to a rectangular waveguide by means of a common hole in the mirror and the shorted end wall of the rectangular waveguide. Closed form expressions have been obtained for the equivalent circuit parameters. Experiments conducted in the W-band frequency range show good agreement with theory when an experimentally estimated correction to the transmission coefficient is applied for the thickness of the coupling holes     

Mutual coupling in finite coplanar rectangular waveguide arrays

Mutual admittance expressions are given for all possible combinations of mode coupling in an array of identical collinear rectangular waveguides opening into an infinite ground plane. Specific results are presented for the worst case of E-plane coupling between identical square waveguide to show that significant high-order mode excitation can occur. Some of these modes are a source of crosspolarisation, making mutual coupling important to the prediction of the crosspolar pattern of a rectangular waveguide array.     

H型金属孔阵列结构强透射折射率传感特性研究

提出了一种H型金属孔阵列结构,利用该结构形成的法布里-珀罗腔加强表面等离激元耦合作用,以期获得较好的强透射现象。采用有限时域差分法(FDTD)对该结构进行数值仿真,并详细研究了H型金属孔阵列中水平方向矩形孔和竖直方向的两相同对称矩形孔的长和宽等参数对强透射特性的影响;同时研究了基于该现象的折射率传感特性。结果表明:当水平方向矩形孔的长和宽分别为300和120nm、竖直方向的两相同对称矩形孔的长和宽分别为60和10nm时,强透射现象较好,并在此基础上获得了389RIU/nm的折射率灵敏度。这些研究结果有望为高性能微纳等离子体传感器的设计提供理论参考。     

Coupling Holes Between Resonant Cavities or Wave-Guides Evaluated in Terms of Volume Ratios

A hole in a common wall is used to provide coupling between two resonant cavities (k=coefficient of coupling) or between two waveguides (x or b=normalized reactance or susceptance) or between cavity and waveguide (p=loading power factor of cavity). Referring to either side of a thin common wall, the field intensity in the center of a small hole is 1/2 what it would have been at that location on the wall. Between two equal regions, the coupling (k, x or b) by magnetic or electric field is expressed as 1/4 the ratio of the effective volume of the hole over the effective volume of each region, by duality (Booker's principle), the effective volume (related to the polarizability) of an aperture in a thin wall is identified with that of an analogous thin body in a uniform field. For a resonant cavity loaded by coupling to a waveguide, the loading power factor is p=kx; this theorem is proved by reference to an equivalent network. Various cases of coupling by two-dimensional and three-dimensional fields are formulated in terms of area or volume ratios, especially between pillbox resonators (rectangular, circular, or coaxial-circular) and between rectangular waveguides with common side walls or top and bottom walls. The effective area or volume of a small hole in a thin conducting wall is given for various symmetrical shapes, in a magnetic or electric field.     

Wave Scattering in Nonuniform Waveguides with Large Flare Angles and Near Cutoff

A set of coupled first-order differential equations for the wave amplitudes in nonuniform waveguides is developed. The coupling coefficients are regarded as differentiaI transmission and reflection scattering coefficients between two adjacent elementary radial waveguide sections. The analysis is an extension of an earlier quasi-optical solution. This set of coupled equations is compared with the familiar generalized telegraphist's equations which may be derived by considering the nonuniform waveguide to consist of elementary rectangular waveguide sections. The equations for the wave amplitudes derived in this paper are less coupled than the commonly used telegraphist's equations, and they may also be applied to waveguides with large flare angles and in regions at which the waveguide modes are at their respective cutoff cross sections.     

Broad-Band Stepped Transformers from Rectangular to Double-Ridged Waveguide

The design of a series of broad-band Tchebycheff-type stepped waveguide transformers from various sizes of standard rectangular waveguides to a double ridged waveguide covering the frequency range of 4750 to 11,000 mc is described. Four separate transformers employing RG-67/U (WR-90), RG-68/U (WR-112), RG-106/U (WR-137), and WR-159 to Airtron ARA-133 double-ridged waveguide have been designed using this technique and cast in aluminum. The complete frequency range is covered by several pairs depending on which sizes of mating rectangular waveguides are desired. The RG-106/U design covers a frequency range of 53 per cent with a maximum VSWR of 1.08, while the other three designs each cover a slightly smaller frequency band with a VSWR not exceeding 1.05. Along with the experimental results obtained, an outline of the design method is given which can be used to design similar transformers between any compatible rectangular and double ridged waveguides.     

Mutual Coupling in Infinite Planar Arrays of Rectangular Waveguide Horns

The radiation admittance and effective power transmission coefficient are derived by a field matching method for arbitrary scan of an infinite array of open rectangular waveguides. Higher order waveguide modes, as well as higher order modes in the free space cell above the array, are included in the field matching problem. The convergence of the solution was studied, and the number of external free space and internal waveguide modes necessary for an adequate answer are given. Numerical results are obtained and compared with previous theory and with experiment for rectangular grids. Comparison is also made with experiment on a triangular grid which exhibited an anomalous notch in the element pattern. The experimental results in both cases seem to substantiate the theory, at least to the extent that could be expected from the small test arrays that were used for the measurements. The comparison indicates that the method of analysis includes all of the necessary features required for the study of mutual coupling effects in infinite arrays of rectangular waveguides having thick walls.     

多端口耦合问题的等效导纳矩阵

本文提出了一种处理多端口耦合问题的有效方法。在该问题中,各端口波导分别通过一耦合孔与耦合区进行耦合。利用矩量法,首先导出了多端口耦合问题的关于传输模和截止模的等效导纳矩阵的计算公式。在此基础上,考虑到截止模加载于端口波导的特性阻抗,经过适当的矩阵运算,得到仅仅关于传输模的等效导纳矩阵。用此方法计算了一个 H 面 T 形接头的等效导纳矩阵和等效电路参数,所得结果与文献[1]们的结果非要吻合。     

Wide Band Metallic Waveguide With In-Line Dielectric Rods

Conventional rectangular metallic waveguides are seldom used at frequencies higher than twice the cutoff frequency because of higher mode propagation. Single-mode propagation is available for a metallic waveguide with arrayed dielectric rods at the center of the waveguide in the frequency under twice the cutoff frequency region using the TE₂₀ mode, and in the frequency over twice the cutoff frequency region using the TE2o mode. If the metallic waveguide and dielectric loss tangent are assumed to be WR-90 (f_c ap6.55 GHz) and 3times10^-4, respectively, then the attenuation constants are smaller than 0.25 dB/m in the frequency range from 7 to 10 GHz, 15 to 16.5 GHz, and from 17.2 to 21 GHz.     

Functional Approximations for Solving Boundary Value Problems by Computer

The use of functional (as opposed to numerical) approximations in solving electromagnetic boundary value problems is presented. Galerkin's method is modified to simplify the choice of trial functions by permitting use of trial functions which do not satisfy certain boundary conditions. A test problem, the dielectric loaded rectangular waveguide, is worked using both the modified and unmodified Galerkin's method with identical results. This method is then applied to the arbitrary waveguide. The cutoff frequencies and computer drawn contour plots are presented for circular, rectangular, triangular and star-shaped waveguides.     

Matching and mutual coupling characteristics of the elements of a finite waveguide array with an impedance flange

Matching and mutual coupling characteristics of the elements of a waveguide antenna array consisting of a finite number of aperture radiators with a finite flange are analyzed. The radiators are formed by semi-infinite cylindrical waveguides of an arbitrary cross section. The array radiates into a plane-layered medium. The solution procedure is based on the single-mode variational approach. Numerical results are presented for an array consisting of nine apertures of rectangular waveguides.     

Properties of a phased array of rectangular waveguides with thin walls

The radiation impedance of an infinite array of open rectangular waveguides has been calculated by a function-theoretic method forHplane and quasi-Eplane beam scanning directions. The mutual coupling between columns has also been obtained. The amplitudes of the coupling coefficients decay asymptotically asr^{-3/2}while the phase difference between successive coupling coefficients approaches that to be expected from free space wave propagation. This asymptotic behavior is independent of waveguide dimensions for both planes of scan. It is similar to the asymptotic behavior of a line-source-excited wave propagating over a lossy surface. This suggests that the interface between an array and free space may in general be treated as such a surface. The coupling coefficients are used to determine the properties of an array, which has a finite number of active elements surrounded by an infinite passive array. Also, the edge effect due to the finiteness of an array is evaluated.     

High-Order Mode Cutoff In Rectangular Striplines (Short Papers)

The higher order mode cutoff characteristics of rectangular stripline structures, with thin center conductors, are discussed. Data are given, using an alternative method of presentation, on the normalized cutoff of the first eleven higher order modes. Discussions are included on the physical reasons why cutoff is aftered for some modes, relative to that in rectangular waveguides, but not for others.     

Analysis of cascaded sections of T junctions between rectangularand circular waveguides

An analysis of the cascaded sections of a number of slot-coupled T junctions between rectangular and circular waveguides is presented, taking into account the mutual interactions of all possible modes generated by the discontinuities as well as the effect of wall thickness. The formulation is based on solving a set of coupled integral equations resulting from the boundary conditions at the two interfaces of the waveguide sections representing the coupling slots. The integral equations are transformed into sets of matrix equations using the moment method with entire basis and testing functions. Numerical results on input VSWR (voltage standing wave ratio) and coupling are presented for the case of a cascaded section of two air-filled T junctions for different frequencies and different values of interelement spacing     

Cutoff wavelengths and frequencies of standard rectangular waveguides

The errors arising from the customary assumption that standard rectangular waveguides have perfectly rectangular cross-sections and are operated in vacua are discussed. Correct cutoff wavelengths and frequencies for 36 standard waveguides in air are tabulated; the values given deviate from the customary ideal values by as much as 0.9%.