Design of slot arrays in waveguide partially filled with dielectric slab

The Elliot procedure for the design of a waveguide slot array is extended to the case of partially filled radiating waveguides. The dielectric slab lies on the top of the radiating waveguide, i.e. on the slotted wall. The proposed solution prevents some of the most common drawbacks of waveguide slot arrays. Results are validated against a commercial FEM software.     

Scattering from a dielectric of finite length

The purpose of this work is the treatment of the problem of scattering from a finite length dielectric cylinder with dimensions comparable to the wavelength of the incident field. This is a general consideration of the problem, in contrast with previous papers which deal with infinite or thin scatterers or simple polarizations. To handle the problem, the integral equation approach and the dyadic analysis are used. The numerical treatment is based on the method of moments, and results are obtained for the case of broadside incidence at three different frequencies.     

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.     

The design of a slot array in nonradiating dielectric waveguide, part I: Theory

A set of theoretical design equations for a slot array fed by nonradiating dielectric (NRD) waveguide is developed. Mutual coupling between the slots cut into one of the metal walls of the waveguide is taken into consideration for a design that can have a predetermined radiation pattern. The theoretical development follows that of Elliott.     

The design of a slot array in nonradiating dielectric waveguide, part II: Experiment

Measurement procedures for obtaining the self-impedance of an isolated inclined radiating slot in the metal wall of a nonradiating dielectric (NRD) waveguide are discussed. The design procedure for an antenna array fed by NRD-waveguide and making use of this information is described. As an example, the design, construction and evaluation of a ten-element input-matched broadside linear array is described.     

Excitation of an electrically thick metamaterial waveguide of a finite length

The problem of diffraction of a cylindrical wave by a plate whose medium has a negative refractive index (a metamaterial) is numerically solved. The near and far fields are investigated for the case when a cylindrical wave source is located near the narrow butt-end of a long plate and when the metamaterial of the plate has various values of the permittivity and permeability. The results obtained are interpreted in terms of the geometric optics. It is shown that a plate made from such a metamaterial can be applied for fabricating antennas with multi- and single-lobe patterns.     

Analysis of a centered-inclined waveguide slot coupler

Integral equations are developed for a centered-inclined coupling slot (including the effect of finite wall-thickness of the common broad-wall) and the slot-aperture electric intensity field is found using the method of moments. Numerical results for resonant length, backscattered wave amplitude, and phase variation off-resonance are presented over a range of values of the waveguide b dimension, wall thickness, slot width, and frequency. It is shown that the resonant length is relatively insensitive to slot tilt, &thetas;, for a standard-height X-band waveguide, whereas its dependence on &thetas; is significant for reduced-height waveguides. The phase variation of scattered TE₁₀ waves in both waveguides off-resonance is less for wider slots and smaller b dimensions. Shunt-series coupling slots exhibit greater phase variation off resonance when compared to a centred-inclined coupling slot. Also, the former has a longer resonant length for a smaller b dimension and for a wider slot. Thus the centred-inclined slot coupler possesses superior characteristics. The higher-order mode coupling between a centred-inclined slot coupler and a pair of straddling radiating slots in the branch waveguide is significant     

Nonradiative dielectric waveguide with perforated dielectric strip

The properties of a nonradiative dielectric waveguide with a dielectric strip perforated by a series of holes are described. The perforated guide can be used in instances where different wave impedances are desired, in addition to where different propagation velocities are needed without resorting to the use of physically different materials.     

Analysis of a terminated parallel-plate waveguide with a slot in its upper plate

A slotted parallel-plate waveguide, terminated in a specified load, is analyzed in this paper. The guide is excited by an interior tem wave and illumination from an exterior source. An integral equation is developed for the unknown electric field in the slot and it is solved numerically for several cases of interest. Values of slot electric field, scattering parameters, and the far field radiated through the slot are presented graphically.     

COUPLING PROPERTIES OF THE SLOT IN A WAVEGUIDE JUNCTION

The coupling properties of a transverse slot in the common wall between two buttingrectangular waveguides are discussed.By means of Galerkin's method which takes into accountthe wall thickness,equivalent magnetic currents on the aperture surface of the slot are obtained,and then the general formulae of scattering fields and of equivalent parameters are derived.Thedimensions as well as seats of those two waveguides and the slot,and the thickness of the wall arearbitrary.For example,the transforming coefficients and the VSWRs of numerical calculationand experimental results are given.They are in good agreement.     

FDTD solution of Maxwell's equations for an edge slot penetratingadjacent broadwalls of a finite wall thickness waveguide

The finite-difference time-domain (FDTD) method is applied to predict reflection coefficients for edge slots penetrating the adjacent broadsides of thick nailed rectangular X-band waveguides. Measured and calculated values S₁₁ are compared to experiment for waveguides terminated by shorted loads     

Multilayered open dielectric waveguide with a gyrotropic layer

Open dielectric waveguides with a gyrotropic layer have been studied with a view to find structures in which the nonreciprocity in the propagation constant is maximized. A prediction based on a qualitative analysis and numerical studies for confirming the theory are included.     

Diffraction of guided waves by the end face of a dielectric slab waveguide terminated with a finite conductive strip

The diffraction of guided waves by the end face of a dielectric slab waveguide short circuited with a finite conductive strip is analyzed. An integral equation technique is employed to formulate the corresponding boundary problem. The unknown term in this integral equations is the electric field E(x) on the terminal plane of the waveguide. The homogeneous term is determined from the incident guided wave. A method of moments technique is employed to compute approximately the electric field E(x) by using Laguerre functions as describing and testing functions. The reflection coefficients of the guided waves are computed by using the approximate expression of the E(x) field. Numerical results are given for several guide and conductor plate dimensions.     

非均匀网格FDTD分析波导宽边辐射缝隙特性

波导宽边辐射缝隙被广泛应用于波导缝隙阵列中，为了比较准确地对波导缝隙进行建模，同时考虑到计算资源限制，本文引入一种采用非均匀网格的时域有限差分方法对其S参数特性进行了计算。数值结果表明该方法分析波导辐射缝隙特性问题的有效性。     

Excitation of an open resonator coupled with a waveguide via a slot in a mirror

A technique and results of the solution of the problem on excitation of an open mirror resonator coupled with a waveguide via a slot in one of the mirrors are presented. The effect of the coupling slot on the radiation loss is analyzed. The results obtained with the help of a rigorous approach and approximate techniques are compared.     

A dielectric rod waveguide coupled with metal rectangular waveguide

Measurements have been done in the millimeter wave region on a composite waveguide which comprises a dielectric rod waveguide connecting two metal rectangular waveguides. Such a waveguide has been used by us in a Josephson harmonic mixer installed in a small metal cryostat, to prevent the thermal invasion from outside environment and to transmit both signal and LO waves with small losses. The measured transmission loss, that is caused mainly by the coupling loss between metal rectangular waveguides (TE₁₀ mode) and a dielectric rod waveguide (HE₁₁ mode), has been less than 2dB in the frequency range of 52–104 GHz.     

Analysis of irregularities in a planar dielectric waveguide

A numerical method based on the partial variational principle (PVP) is proposed to solve discontinuity problems due to arbitrary irregularities in a planar dielectric waveguide. A variational equation is established and solved by the finite-element method along with the Green's-function technique. The integral variable of the Green's-function is changed so that numerical calculations can easily be performed. Because of the accuracy of the present method, the radiation fields can be obtained with no difficulty. Several numerical results, including the reflection and transmission coefficients as well as the radiation losses and patterns, are calculated and compared