Numerical analysis of centered-inclined coupling slots in rectangular waveguides

Waveguide coupling and radiation by means of apertures is modelled using a hybrid technique which combines the finite element method with the moment method. Unlike the conventional pulse expansion and point matching technique, it ensures the convergence of the resultant admittance matrix elements without introducing any assumptions about the field distribution on the apertures. Coupling and radiation problems formed by a conventional transverse slot in rectangular waveguide and a complex T-shaped slot in a bifurcated waveguide are examined respectively, and excellent agreement has been obtained for both cases when compared both with alternative theoretical predictions and with measurements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.

A complete analytic array design process [1] with slots fed by dielectric filled waveguide requires accurate prediction of slot characteristics. A theoretical analysis of a longitudinal slot on the wall of a rectangular waveguide was given by Vu Khac [2] and Vu Khac and Carson [3]. It is assumed that the magnetic current J has no variation along the narrow dimension of the slot. This assumption violates the edge condition and therefore reduces the accuracy of the final results. In this paper we formulate the same problem with the edge condition and analyze slots.

In this paper, the admittance characteristics of a dielectric filled inclined slot in the narrow wall of a rectangular waveguide have been calculated. By enforcing the continuity of the tangential magnetic field through the slot aperture, an integral equation with the tangential electric field in the slot as the unknown is obtained. An entire domain method of moments (MoM) is used to solve the integral equation. Numerical results show that the slot can resonate without penetrating onto the top and bottom broad walls of the waveguide. It has also been shown that the resonant frequency (length) and the resonant conductance of the slot depend on the dielectric constant of the material filling the slot. The computed results are shown to be in good agreement with those obtained by HP‐HFSS. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 222–226, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10876

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.

The longitudinal slot in a rectangular waveguide is solved by the moment method, where the transverse variation of the tangential electric field on the apertures of the slot contains the correct edge behaviour. It is shown that three expansion functions are enough for an excellent convergence and accuracy of the solution.

With the advantage of small volume, light weight, high aperture efficiency and low side lobes, The Antenna Array of Slots in Rectangular waveguide is widely used in many microwave communication systems that requires narrow beam and shaped beam. This paper analyses the structure and design procedures of antenna array of slots in the narrow wall We first obtain the physical size of each slot by using the parameter sweep function of the Ansoft HFSS software. Then we created a complete model. Finally, we perform the simulation and compare against the design requirement There is a good agreement between simulation and design requirement.

The leaky-wave antennas in the form of closely spaced transverse slots cut in a broad wall of rectangular waveguide were investigated. The thickness of waveguide walls and interaction between slots were taken into account in numerical calculations.

Arrays of broadwall shunt slots in rectangular waveguides

Technique is proposed for the calculation of radiation field from a slot in a rectangular waveguide, the slot shape being nonrectangular. The technique is based on a boundary-value problem formulation in terms of Hertz electric and magnetic potentials introduced for the interior and exterior domain of the slot and for the slot space as well.

We have studied the electrodynamic and focusing dependence on the coupling slot and coupling cell parameters for circular and rectangular accelerating structures. We find that: (i) for circular structures the coupling slot induced asymmetric electromagnetic fields of the coupling cell have twice the influence on the transverse beam dynamics than those of accelerating cells; (ii) the neighboring cell coupling slot location can influence the beam dynamics from minimally to usefully; and (iii) by increasing the coupling slot area while optimizing its geometry and decreasing the coupling cell area covered by surface currents, the coupling can be increased /spl sim/15% with little decrease in shunt impedance.

This paper presents, method of moments based analysis of broad-wall longitudinal slots array antenna using Multiple Cavity Modeling Technique (MCMT). Theoretical data for reflection coefficient, transmission coefficient, resonance length and resonance conductance have been obtained for two slots in two different waveguide. The theoretical data have been compared with Ansoft HFSS's simulated data to validate the proposed method. The excellent agreement obtained between the results demonstrates that the proposed method is able to accurately and efficiently solve complex reflection coefficients and transmission coefficients for different slot parameters. In this paper we have analyzed a two element planar broad-wall longitudinal slots array antenna based on Multiple Cavity Modeling Technique (MCMT) (15). The theoretical data have been compared with the Ansoft HFSS's simulated data to validate the proposed method. The excellent agreement between the results demonstrates that the proposed method is able to accurately and efficiently solve complex reflection coefficients and transmission coefficients for different slot parameters.

Based on the need for the design of planar arrays with three-layer structure (feeding slot, coupling slot, radiating slot), theoretical analysis of the radiation pattern of a slot-fed longitudinal slot array in the broadwall of a rectangular waveguide with shorted terminals is presented. When analyzing and synthesizing the array, the fundamental integral equations that describe the array are used directly. Mutual coupling between the coupling slot and radiating slots, and internal and external mutual coupling between radiating slots, and the finite waveguide wall thickness, are included as integral parts of the development. The results of the synthesis are presented to illustrate the advantages of the new method for the synthesis of the slot array in a rectangular waveguide with shorted terminals.

A resonant coupling slot cut in the common broad wall of two crossed rectangular waveguides is analyzed. The slot is offset from the center line and tilted with respect to the longitudinal axis of the main waveguide, whereas it is centered-tiled in the branch waveguide. It is shown that the slot offset and tilt control the branch waveguide excitation amplitude with a phase variability of 360 degrees . Pertinent integral equations are developed, taking into account finite wall thickness. The integral equations are solved for the slot aperture electric field using the method of moments. Dominant mode scattering by the slot in both waveguides is obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An accurate computation of the admittance characteristics of longitudinal shunt slots in a rectangular waveguide is presented. A moment method with entire basis functions is used for solving the electric field in the slot. The waveguide wall thickness is accounted for by introducing higher order waveguide modes in the short waveguide connecting the inner and outer regions. Particular attention is given to the resonant length of the slot, which is a critical parameter in the design of waveguide slot array antennas. Computed resonant lengths compare very well with measured results.