Broad Wall Of Rectangular Waveguide Research Articles

SUBWAVELENGTH SPIRAL SLOTTED WAVEGUIDE ANTENNA

Integrating antennas into a load-bearing airframe structure has the potential for profound improvements in the capability of military and commercial airplanes, by allowing for substantially increased radiator and array size with reduced weight or drag penalties. Reducing the size of array elements can significantly improve the mechanical performance of the loadbearing antenna. The novel single element spiral slot cut in the broad-wall of a WR-90 rectangular waveguide proposed in this paper is smaller than a quarter of the operating wavelength (half of the size of a conventional rectangular slot). The small antenna element enables a slotted waveguide array to be realized without significantly degrading the mechanical performance in load bearing applications. The proposed spiral slot is compared with conventional rectangular slots and exhibits comparable performance in terms of total efficiency (representing coupling from waveguide mode to the slot) and peak realized gain. Total efficiency and peak realized gain of the spiral slot in travelling wave mode are significantly higher than those of a quarter wavelength rectangular slot element which has near zero radiation. The simulated results were validated by manufacturing the spiral slot placed on the broad-wall of a rectangular waveguide. Realized gain patterns of the spiral slot measured at the design frequency corroborate reasonably with the simulations.

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.

COMBINED VIBRATOR-SLOT STRUCTURES IN ELECTRODYNAMIC VOLUMES

The problem of excitation of electromagnetic flelds by a material body of flnite dimensions in presence of coupling hole between two arbitrary electrodynamic volumes is formulated. The problem is reduced to two-dimensional integral equations for the surface electric current on a material body and the equivalent magnetic current on a coupling hole. A physically correct transition from the initial integral equations to one-dimensional equations for the currents in a thin impedance vibrator which, in general case, may have irregular geometric parameters, and a narrow slot is justifled. A solution of resulting equations system for the transverse slot in the broad wall of rectangular waveguide and a vibrator with variable surface impedance in it was found by a generalized method of induced electro-magneto-motive forces. The calculated and experimental plots of electrodynamic characteristics of a vibrator-slot structure in a rectangular waveguide are presented.

Design and Optimization of Waveguide-Fed Centered Inclined Slot Arrays

A new method is presented for the design and optimization of standing- and traveling-wave-fed centered inclined slot arrays, cut on the broad wall of rectangular waveguides, based on the method of least squares (MLS). Utilizing the two available design formulas for the standing-wave-fed array, we have extended the design procedure to the traveling-wave-fed arrays including nonuniformly spaced slots. As a common approach in MLS an error function is formulated consisting of three terms (namely those for the input impedance matching, design equations and pattern synthesis). The error function is then minimized with respect to the design parameters using the hybrid method of genetic algorithm and conjugate gradient method. By combining the ldquopattern synthesisrdquo with ldquoimpedance matchingrdquo and ldquocalculation of array parameters,rdquo this procedure increases the design speed as well as synthesizing any desired pattern. The MLS design results and those obtained by HFSS and CST simulation software are in agreement and verify the accuracy of the proposed method.

A nonuniform array of slots in the broad-walls of rectangular waveguides partially filled with dielectric slabs

This article describes a new nonuniform slot antenna array in the broad wall of rectangular waveguides partially filled with a dielectric slab. The slot elements are nonuniformly spaced to achieve ...

DESIGN AND OPTIMIZATION OF NONUNIFORMLY SPACED LONGITUDINAL SLOT ARRAYS

A new numerical method is presented for the design and optimization of linear arrays of nonuniformly spaced longitudinal slots on the broad wall of rectangular waveguides, based on the Method of Least Squares (MLS). Elliott’s design theory for travelling-wave-fed slot arrays is extended to nonuniformly spaced slots. As a common approach in MLS, an error function is formulated according to the design goals (namely the input impedance matching and pattern synthesis) and then minimized with respect to the design parameters (namely slot lengths, offsets, spacings and excitations). Having the slot parameters, one can design a linear slot array which accounts for the desired input impedance matching and array pattern. This approach has the advantage of combining the “nonuniform pattern synthesis”, which includes the external mutual coupling and element pattern of slots, with “impedance matching” and “calculation of the array parameters”. This procedure increases the design speed as well as synthesizing any desired pattern. The MLS design results and those obtained by HFSS simulation software are in good agreement and verify the accuracy of the proposed method.

ANALYTICAL METHODS IN THEORY OF SLOT-HOLE COUPLING OF ELECTRODYNAMIC VOLUMES

The approximate analytical solution of the integral equation concerning the equivalent magnetic current in the narrow slot, coupling two electrodynamic volumes, has been obtained by the averaging method. The formulas and the plots for currents and the coupling coefficients of longitudinal and transverse slots in the common walls of rectangular waveguides are represented. By means of the induced magnetomotive forces method using basis functions of current distribution, obtained by the averaging method, the following electrodynamic structures have been considered: the electrically long longitudinal slot in the common broad wall of rectangular waveguides; two symmetrical transverse slots in the common broad wall of rectangular waveguides; the transverse slots system in the common broad wall of rectangular waveguides. The problem about the resonant iris with the arbitrary oriented slot in the plane of cross-section of a rectangular waveguide has been solved by the averaging method. The problem about stepped junction of two semi-infinite rectangular waveguides with the impedance slotted iris has been solved by the induced magnetomotive forces method. The analytical formulas for the distributed surface impedance of homogeneous and inhomogeneous magnetodielectric coatings of iris surface have been obtained. For a greater number of the considered electrodynamic structures the calculated values are compared with the results, obtained by numerical methods (also using commercial programs) and the experimental data.

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.

Planar Elliptical Nonresonant Array for Airborne Radar Applications

This paper describes the work carried out at Electronics and Radar Development Establishment towards the design and development of the airborne ultra-low sidelobe level antenna for radar applications. This elliptical contoured antenna employs longitudinal offset radiating slots on the broadwall of rectangular waveguide and is of travelling wave type. Studies have been made on the effect of slot width on the bandwidth of the nonresonant array. The radiating elements are fed by a compact waveguide power divider network. The design aspects of the power divider and the phase compensation network have been outlined. The details of the elliptical planar array antenna with the measured far-field results have been presented.

Design and Development of Ultralow Sidelobe Antenna.

This paper describes the design and development of an airborne ultralow sidelobe level antenna, starting from the design of individual linear arrays and the power divider network. The antenna employs radiating slots on broadwall of rectangular waveguide and is of traveling wave type. The various stages involved in the design process are described briefly. The experimental results including the far-field patterns, voltage standing wave ratio, and power division ratios are discussed in detail.

A hybrid analytical technique for radiating slots in waveguide

A hybrid technique which combines the finite element method with the moment method is proposed for the analysis of radiating slots as used in slotted-waveguide array antennas. It differs from earlier contributions to this topic in that it formulates the field in the slots in terms of a functional, rather than a Green's function or combination of higher order waveguide modes which are generally used in conventional moment methods. It is, therefore, a promising candidate for the analysis of radiating elements of complex shape as used in, for example, circularly polarized and polarization selective slotted-waveguide array antennas. A conventional longitudinal slot in the broad wall of rectangular waveguide and a complex T-shaped slot in bifurcated waveguide have been modeled to demonstrate the validity of the hybrid technique. The numerical results are shown to be in good agreement with those obtained from independently procured theoretical evidence and measurement.

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.

Longitudinal slots in broad wall of rectangular waveguide inhomogeneously loaded with dielectric slab

Computed and measured results are shown for the scattering and equivalent network properties of longitudinal slots in the broad wall of a rectangular waveguide inhomogeneously loaded with a dielectric slab. The formulation used involves the moment method solution of a pair of coupled integral equations containing the dyadic Green function of the inhomogeneously loaded waveguide as a kernel.

Conductive contacting spheres on the centre of the broad wall of rectangular waveguides

It has been found that metallic balls (held by external magnets) in rectangular waveguides produce a frequency-independent reflection, and an empirical formula is given for the magnitude of the reflection coefficient.