Slot In Broad Wall Research Articles

A Reciprocity Method of Analysis for Gap Waveguide Slot Antennas

This paper introduces analytical solutions to gap waveguide slot antenna structures. The reciprocity method is used for the analysis by exploiting Green’s function of a bed of nails structure employing a homogenized plane-wave spectral-domain approach. Green’s function is found using parallel plate waveguide and surface admittance concepts. The spectral surface admittance of the pin structure is calculated using asymptotic boundary condition (ABC), and the unknown antenna slot currents are solved using moment methods. The structure is designed to have a cutoff frequency of 10–15 GHz, and the central operating frequency of the slot is 12.5 GHz. This approach is applied to the specific geometry of a propagating ridge gap waveguide single transverse broad wall slot antenna structure. The equivalent series impedance and far zone fields and patterns are calculated, and the results are compared with a full-wave commercial software, and they are proved to be accurate.

Optimum design of travelling rectangular waveguide edge slot array with non‐uniform spacing

Slot arrays on the narrow wall of rectangular waveguides are designed for the realisation of arbitrarily specified radiation patterns. The derivation of design equations is similar to the procedure introduced by Elliott for the broad wall slots. An error function is constructed having four terms: impedance matching, array pattern synthesis, slot design equations and radiation efficiency. The minimisation of the error function is performed by the combination of genetic algorithm and conjugate gradient method, which determines the geometrical dimensions of slots, such as their slant angles, lengths and spacings. The performance of designs by the proposed method of least squares is verified using full-wave simulation software.

ELECTROMAGNETIC WAVES SCATTERING AND RADIATION BY VIBRATOR-SLOT STRUCTURE IN A RECTANGULAR WAVEGUIDE

A problem of electromagnetic waves scattering and radiation by a structure, consisting of a narrow transverse slot in broad wall of rectangular waveguide and a vibrator with variable surface impedance, located inside the waveguide and interacting with one another, is solved. A solution of integral equations for electric current on the vibrator and equivalent magnetic current in the slot is derived by the generalized method of induced electro-magneto- motive forces. Conditions necessary for achievement of maximal slot radiation coe-cient are deflned. Efiectiveness of impedance vibrators application to ensure required level of radiation by vibrator-slot structure in low proflle rectangular waveguides is shown. Calculated and experimental plots of energy characteristics of the vibrator-slot structure for difierent vibrator placement relative to the slot and for various surface impedance dependencies upon the vibrator length are presented.

Connected Post-Wall (C-PW) Waveguide for Efficient Design of Broad Wall Slots by Using Equivalent Solid-Wall Waveguide

Post-wall waveguide slot arrays are potential candidates for millimeter-wave systems. The modeling of the post-walls by the equivalent solid-walls in terms of guided wavelength is indispensable for intensive optimization of slot design for reducing computational load. In the single mode waveguide slot arrays, the modeling errors of the post-wall waveguide by the solid-wall waveguide are serious especially for the transversely located slots. The S-parameter prediction errors become larger as we increase the height of the waveguide to utilize the low-loss advantage of the waveguide. The authors propose a novel post-wall waveguide structure, named as a connected post-wall (C-PW), to enhance the equivalence. The C-PW waveguide keeps enhanced equivalence to the solid-walls even for a larger substrate height. The predictions are confirmed by simulations and measurements. An 8-element linear array of reflection-cancelling slot pairs is designed by using the equivalent solid-wall model to demonstrate the feasibility of the simple design in the C-PW.

CHARACTERISTICS OF AN OFFSET LONGITUDINAL / TRANSVERSE SLOT COUPLED CROSSED WAVEGUIDE JUNCTION USING MULTIPLE CAVITY MODELING TECHNIQUE CONSIDERING THE TE00 MODE AT THE SLOT APERTURE

A moment method analysis of a broad wall slot coupled crossed rectangular waveguide junction has been presented in this paper. The coupling slot is longitudinal/transverse and offset from the centre lines of the guides. The integral equations, governing the characteristics of the device, have been obtained using Multiple Cavity Modeling Technique, taking into account of the finite wall thickness and the TE00 mode at the slot apertures and have been solved using Moment Method to obtain the aperture distribution. The normalized resonant lengths/complex S-parameters have been calculated from this field distribution for different guide height/slot offsets/slot widths/slot thickness of the longitudinal/transverse slot over the frequency band. Numerical data, thus obtained, have been compared with measured/literature available/CST Microwave Studio Simulated data. The theory has been validated by the reasonable agreement obtained between them. It has been shown that, neglecting the TE00 mode at the slot apertures can adversely effect the estimation of the resonant frequency and equivalent network parameters.

Full-Wave Analysis of Broad Wall Slot's Characteristics in Rectangular Waveguides

A rigorous analysis of the resonant characteristics for a broad wall waveguide slot by using the finite-difference time-domain method is presented. Four types of slots including a radiating longitudinal shunt slot, a longitudinal/transverse coupling slot, a centered-inclined coupling slot and a compound coupling slot are analyzed. Lots of slot characteristics such as the resonant length, scattering parameters and normalized admittance in different offsets, tilt angles or slot sizes are obtained. Because the shape of slots is a rectangle with rounded ends in practical fabrication, an accurate modeling and computation for the slots with rounded ends is implemented, and the resonant lengths calculated coincide well with the Stegen's measured data and method of moments results. From these computed results, it is found that all the resonant characteristics of the slots with rounded ends are significantly different from those with normal rectangular ends.

A Design of Magic Tee with Coplanar Arms

Magic tee is a widely used component in microwave systems; the four arms of conventional magic tee direct at four different directions, which give inconveniences to the assemblage of a system. In this paper, a broad-wall slot directional coupler and an E-plane dielectric loaded waveguide phase shifter is used to form a magic tee with four arms in the same E-plane. The magic tee is analyzed exactly with mode match method; and the simulated annealing method is used to optimize the performance of the magic tee. Simulation results are presented, which show good performance.

Analysis of Coupling Using a Transverse Slot in the Common Broad Wall between Two Waveguides

The variational method is used in the present paper to derive the expressions for the complete equivalent circuit of a central transverse slot in the broad wall of a rectangular waveguide. The magnetic field is found from the vector potential involving waveguide (internal) dyadic Green's function. The expression for the self-reaction between the magnetic field and the magnetic current appears in the form of infinite double summation. The double summation appearing in the expression for the self-reaction is simplified to a series, which converges very rapidly. Numerical data evaluated using a complete equivalent circuit is presented.

ANALYSIS OF BROADWALL SLOTS IN FINITE WALL THICKNESS WAVEGUIDE WITH NON-UNIFORM MESH LOCALLY CONFORMAL FDTD

A non-uniform mesh locally conformal FDTD (NUMLC-FDTD) technique is applied to analyze the properties of arbitrarily shaped broadwall slot with less computational costs. The NUMLC-FDTD method divides the whole computation domain into fine and coarse mesh domains and in fine mesh domain Faraday's law is applied in different cell regions according to different types of distorted cells. Mutual coupling of the doublet bulletedheaded slots is analyzed and numerical results demonstrate the efficiency as well as the accuracy of the method.

Waveguide‐fed longitudinal slot array antennas: Fault diagnosis using measurements of input impedance

AbstractThis communication presents a method of locating defective elements of longitudinal broadwall slot array antennas. The method assumes defects to consist of partial obturation of the slots, and is based on measurement of the input impedance of the antenna. A genetic optimization algorithm finds the configuration of defective elements that best corresponds to the measured impedance. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 200–201, 2002.

Iterative FEM for characterising radiating slot in broad wall of rectangular 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.

Bifurcated waveguide fed broadwall slots radiating through a baffle

A recent innovation in the development of slotted-waveguide array antennas has shown that for a rectangular waveguide radiating into a ‘half-space’ through slots located in the broadwall, polarisation selectivity can be achieved by even or odd mode excitation of a suitable combination of longitudinal and transverse slots in an axially bifurcated form of the waveguide. In practice, however, the external region of the guide is seldom a true half-space, particularly in the case of linear arrays, which are often modified by a short section of parallel plate waveguide to provide some degree of polarisation purification and/or spatial filtering. An analysis of this geometry is described here, in which the presence of the parallel plate region has been accommodated within a moment method model of a polarisation agile slot arrangement by employing an ‘imaged’ Green function to represent the parallel plate enclosure. It is also shown that particular care in identifying suitable basis functions is required in the case of the T-shaped element of the polarisation agile slot pattern which straddles the waveguide bifurcation.

Moment method analysis of a horizontally polarised omnidirectional slot array antenna

An entire domain moment method analysis of an omnidirectional linear array antenna, in which the radiating elements are slot doublets in a rectangular waveguide, has been developed. A particular feature of the analysis is that direct computation of internal mutual coupling between broadwall slots on opposing walls has been incorporated. Numerical solutions are presented for the scattering properties of the slot doublets in both air-filled and dielectric-filled waveguides. The results are shown to be in good agreement with network analyser measurements.

Broadwall slot coupling into butt‐ended waveguide

AbstractWe present an analysis of a slot cut in a broadwall of a rectangular waveguide, coupling into a semiinfinite rectangular waveguide capped by a conducting transverse plate containing the slot. Slots coupling into butt‐ended waveguides are employed in test fixtures in slot array applications. Pertinent integral equations for the slot‐aperture electric field are solved by the method of moments, and scattering characteristics of slot couplers for butt‐ended guides are deduced. Numerical results indicate limitations of these couplers for applications involving reduced‐height guides. © 1994 John Wiley & Sons, Inc.

Rigorous analysis of weakly excited broadwall slots

The choice of basis functions is found to be critical in the accurate modelling of weakly excited slots. Pulse expansions and the point matching technique are found to be inadequate, whereas polynomial basis functions in the Galerkin method are found to yield very accurate solutions.

Broadwall-to-Broadwall Coupling between two Cross Rectangular Waveguides through an Offset Slot

The problem of coupling through a slot in the broadwall between two rectangular waveguides has been investigated and Method of Moments used to find the co-efficients of the field function. Convergence of solution requires inclusion of thousands of waveguide modes in the numerical solution. Number of basis functions less than 10 usually gives less accurate result in the computation of slot admittance. The resolant length has been found to change noticeably with offsets.

Efficient and accurate evaluation of external mutual coupling between 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. >

Longitudinal component of aperture electric field in weakly-excited broadwall slot

For longitudinal slots cut in rectangular waveguides, the longitudinal component of the aperture electric field is found to be significant when the offset is small even for narrow slots. Ignoring the E-longitudinal component can introduce substantial error in the computed scattering parameters for weakly excited slots.

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.

Scattering analysis of a waveguide slot radiator enclosed in a parallel plate polariser

The moment method of analysis as applied to conventional broadwall slot radiators in rectangular waveguide has been extended to accommodate the presence of an external parallel plate polariser. This has been achieved by imaging the half space Green's function, which is used in the conventional analysis, in the ‘perfectly’ conducting parallel planes. The results obtained are shown to be in good agreement with vector network analyser measurements on typical geometries.