The impedance properties of dielectric-covered narrow radiating slots in the broad face of a rectangular waveguide

An extension of Oliner's theory is used to predict the impedance of slots with dielectric coatings. Theoretical curves are presented which show the change in impedance as a function of dielectric constant, dielectric losses, and dielectric thickness. The effect of a dielectric or plasma upon the resonant frequency is also included. The agreement with experimental dielectric-covered slot data justifies the extension of Oliner's theory.     

Circularly polarised radiation from narrow wall slots in rectangular waveguide

Slots in rectangular waveguides are often used at elements in linear array antennas. The polarisation of the radiated energy is usually linear. Circular polarisation can be obtained with compound slots in the broad wall. Experiments have shown that circular polarisation can be obtained from certain I-shaped slots in the narrow wall.     

Analysis of edge slots in rectangular waveguide with finitewaveguide wall thickness

A novel analysis for computing the admittance characteristics of edge slots with a salient feature in successfully considering the finite waveguide wall thickness is presented. The variational equation for the electric field in the slot region between the inner and outer waveguide walls is derived by applying the variational reaction theory and solved by the finite-element method. The division of the slot region into small elements of triangular cylinders and the basis function for each element are described in detail. In the limiting case of zero wall thickness, this finite-element analysis is reduced to a moment-method analysis using Galerkin's approach with triangular basis functions. The effects of waveguide wall thickness on the characteristics of the slot are investigated by comparing the numerical results with and without considering the wall thickness. Negligence of the wall thickness may result in a severe underestimation of the resonant length by as large as 14% for edge slots cut in typical X-band waveguides. The computed results with the finite wall thickness taken into account have been checked with the measured data published in previous literature and those obtained by a carefully devised experimental setup. Good agreement between theoretical and experimental results is obtained to demonstrate the validity of the analysis     

Resonant conductance of inclined slots in the narrow wall of a rectangular waveguide

A method to determine the admittance and resonant length of an inclined slot in the narrow wall of a rectangular waveguide is presented. An expression for the admittance of the slot is derived using an angular spectrum of planewaves and the discontinuity in modal current. When the depth of cut in the top and bottom wall is assumed to be zero, the expression for resonant conductance found by the present method is exactly the same as that obtained by Stevenson. Comparison between the theoretical and experimental results on the variation of resonant conductance with angle of inclination of slots for a fixed depth of cut of 3.5 mm is presented.     

Iterative FEM for characterising radiating slot in broad wall ofrectangular waveguide

It is shown that the iterative finite element method with the radiation-type boundary condition can give an efficient and accurate solution to the radiation problem. The proposed method is applied to the characterisation of a radiating slot on the broad wall of a rectangular waveguide. The result is compared with those of other conventional methods, and shows a good agreement     

A generalized analysis for a class of rectangular waveguide coupleremploying narrow wall slots

A comprehensive analysis is presented which is applicable to the general class of waveguide couplers comprising a dissimilar pair of rectangular waveguide coupled by means of an inclined slot on the narrow wall of the primary waveguide. An entire domain moment method is used to solve a pair of coupled-integral equations for the tangential electric fields on the surfaces of the slot. Three typical examples have been examined to demonstrate the validity of the method. The numerical results are shown to be in good agreement with those obtained from independently procured theoretical evidence and measurements     

Admittance of rectangular waveguide radiating from a conductingcylinder

Theory and experiment are compared for the admittance presented to a rectangular waveguide which terminates at an arbitrary angle in the surface of a conducting cylinder. Two methods are described for calculating the admittance: a single-mode approximation from the modal solution and an alternative asymptotic solution. Using these methods, the effect of aperture orientation on admittance, and the results obtained are compared with the experiment. The single-mode approximation is in good agreement with experimental results for the case when the input waveguide supports the TE₁₀ mode only. The accuracy of the approximate formula for waveguide admittance was also verified. The admittance is shown to be weakly dependent on aperture orientation for moderately large cylinders     

Analysis of radiating slots in a rectangular waveguideinhomogeneously loaded with a dielectric slab

Longitudinal and transverse radiating slots in the broad wall of a rectangular waveguide inhomogeneously loaded with a dielectric slab are analyzed. The formulation used involves the moment method solution of a pair of coupled integral equations containing the dyadic Green's function of the inhomogeneously loaded waveguide. Both an edge-condition for the electric field in the slot aperture and the correct form of the ψ=constant waveguide mode are included in the analysis. Computed and measured results are compared to verify the theoretical analysis     

Eigenwaves of periodic rectangular waveguide with dielectric-filled dips on broad wall

The paper presents a solution of the boundary problem for eigenwaves of periodic structure consisting of rectangular waveguide with dielectric-filled dips on broad wall obtained by Galerkin’s method. The types of waves are analyzed with due regard for the symmetry of structure and field. The results of calculations of basic characteristics of eigenwaves in the baseband are also presented.     

Form of field in small-offset longitudinal slot in broad wall of rectangular waveguide

A surface-patch moment method approach is used to examine the electric field distribution in longitudinal slots that have small offsets from the host rectangular waveguide centreline. It is shown that the phase of the transverse electric field in the slot may display a large variation across the slot narrow dimension in such instances.<>     

矩形波导窄边缝隙分析方法述评

对矩形波导窄边缝隙的各种分析方法进行了综述,并指出了它们存在的问题。从中可以看到这一问题的理论分析方法的进步和尚需解决的问题。     

有限元\\边界元混合算法分析波导裂缝阵列天线

研究了一种分析波导裂缝阵列天线的方法。将有限元-边界元混合算法（FE-BI）应用于波导裂缝阵列天线的计算中,建立理论分析模型,计算波导裂缝上的等效磁流,进而求解整个天线阵列的远场辐射特性。为了检验这种方法的正确性,将所得的数值计算结果与测试值进行了比较,结果表明：FE-BI法可以作为计算波导裂缝阵列天线的一种有效的方法。     

On Lewin's theory of waveguide coupling by rectangular slots

It is shown that Lewin's waveguide coupling formula, when suitably modified, is in good agreement with the results obtained by variational methods. The connection between the modified Lewin formula and the results of the Bethe-Cohn theory is pointed out. It is doubtful if Lewin's theory can be improved to yield the correct slot length for resonance.     

Transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with a dielectric slab

A compact and wide-band transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with an H-plane -dielectric slab is presented in this paper. By partially filling an H-plane dielectric slab in the waveguide, the inter-element spacing between slots is reduced to be about 0.8 free-space wavelengths to avoid grating lobes. In addition, the partially filled material provides extra flexibility to adjust the slot impedance as desired within a relatively wide frequency range. A new feeding network is designed for this antenna array, which can prevent the shift in the pointing angle of the array's main radiation beam with the change of frequency. Experimental data for a 2/spl times/4 antenna array operating at X-band show that stable radiation pattern over a wide frequency range can be obtained. The measured gain is 16.9 dB at 10 GHz and the fluctuation is less than 2 dB over a frequency band of 1.5 GHz. The slot array's 10-dB return loss bandwidth is 13% and the cross-polarization level is better than -25 dB.     

Analysis of edge slots in rectangular waveguide using finite-difference time-domain method

A finite-difference time-domain (FD-TD) method for analysing edge slots in rectangular waveguides is suggested. The proposal is supported by an example.<>     

Admittance and resonant length of inclined slots in the narrow wallof a rectangular waveguide

The admittance properties and the resonant length of an inclined slot in the narrow wall of a rectangular waveguide have been investigated. The depth of cut of the slot in the broad walls of the waveguide has been taken into account. The internal power storage in evanescent modes in the waveguide, neglected in previous studies, is included. Theoretical results for the variations of conductance and resonant length with the angle of inclination of slots are presented. Through comparisons of the calculated results with previously available experimental data, the importance of the inclusion of the waveguide internal power storage is emphasized     

Coupling by slots in rectangular waveguides with arbitrary wall thickness

A method for evaluating the coupling between two rectangular waveguides, coupled by a slot of arbitrary dimensions in a wall of arbitrary thickness is described. The method is based on the solution, by numerical techniques, of a pair of coupled integral equations. Results for typical shunt and series slots are presented.     

Impedance properties of a longitudinal slot antenna in the broad face of a rectangular waveguide

The impedance properties of a waveguide longitudinal slot antenna of arbitrary length and offset in guide walls of finite thickness are investigated. These properties are obtained by treating the slot discontinuity as an electromagnetic boundary value problem and the resulting pair of coupled integral equations are solved by numerical techniques. Results are given for slots having lengths from0.35lambdato1.7lambdaand are in good agreement with experimental results.     

Variational analysis of inclined slots in the narrow wall of arectangular waveguide

A variational analysis for calculating the admittance of the inclined slots in the narrow wall of a rectangular waveguide is presented. The analysis uses the 90° wedge Green's function to model the scatterings off the waveguide corners and assumes an equiphase half-cosinusoidal electric field distribution along the slot aperture. Based on these, a variational equation is derived for the reflection coefficient due to the slot discontinuity, from which the slot admittance is calculated. Through comparisons between the computed results and the literature results, the analysis is found to be accurate, reliable, and efficient