Improvement of conical corrugated horn analysis using Gaussianbeams

The classical analysis of a conical corrugated horn is extended out of the balanced hybrid conditions using a vectorial multimodal Gaussian beam expansion. An experimental validation is also presented     

FDTD analysis of E-sectoral horn antennas for broad-bandapplications

The finite-difference time-domain (FDTD) method is applied to study the performance of E-plane sectoral horn antennas designed for broad-band applications. These antennas (proposed for 6-18 GHz phased arrays) have a large bandwidth, and they are easily array integrated. These antennas have a highly complicated geometry that is modeled using a polygonal approximation in the curved boundaries. Perfect matched layers (PMLs) combined with first-order absorbing boundaries are employed to simulate the free-space environment in the FDTD mesh     

Properties of cutoff corrugated surfaces for corrugated horn design

Corrugated horns involve a junction between the corrugated surface and a conducting groundplane. Proper horn design requires an understanding of the electromagnetic properties of the corrugated surface and this junction. An integral equation solution has been used to study the influence of corrugation density and tooth thickness on the power loss, surface current, and the scattering from a groundplane-corrugated surface junction.     

FD-TD analysis of Vivaldi flared horn antennas and arrays

This paper summarizes a detailed computational study of Vivaldi flared horn antenna designs including single element, double element crossed-pair subarray elements, and linear arrays using the finite-difference time-domain (FD-TD) method. FD-TD, which numerically solves Maxwell's time dependent curl equations, accounts for the complex geometrical and electrical characteristics associated with this antenna design and array implementation. Validations have been made relative to a moment method (MM) model of an electrically large linearly tapered slot antenna. Also, good correlation is shown to exist in the primary features of the antenna patterns between computed and measured data for all cases. This work has achieved a number firsts for the FD-TD methodology. It represents the first “exact” computational model of a single quad Vivaldi slot antenna; the first “exact” computational model of a phased array of Vivaldi quad elements; and the first FD-TD model to demonstrate grating lobes for a phased array antenna of any sort. Lastly, this research represents an extensive study of the largest grid-based antenna models conducted to date     

Accurate analysis of TEM horn antennas for pulse radiation

In the past, various approximate theoretical models have been used to analyze TEM horn antennas. Because of the limitations of these approximate models, there has been, to date, only qualitative agreement of measurements for TEM horn antennas with the predictions of the theories. The finite-difference time-domain (FDTD) method is used to accurately analyze TEM horn antennas for pulse radiation. First, the metallic triangular-plate TEM horn antenna is considered. Computed results for the reflected voltage in the feeding transmission line and the time-varying radiated electric field are shown to be in very good agreement with new experimental measurements. Graphs of the electric field in the space surrounding the antenna (magnitude of field plotted on a color scale) are used to give a physical insight into the process of radiation. Next, the method is used to analyze two TEM horns that were previously designed for pulse radiation. The geometry and electrical properties of these antennas are more complicated than for the metallic, triangular-plate horn. One has shaped metallic plates with a resistive termination at the open end; the other has plates whose resistance varies continuously along their length. The computed results for these antennas are compared with previously made experimental measurements     

Theoretical analysis of cylindrical hybrid modes in a corrugated horn

The propagation behaviour of a corrugated cylinder is considered with particular reference to the application of such structures to hybrid-mode feeds for large reflector antennas. Results are presented which relate to the design of narrow-flare-angle horns of circular cross-section. These include the parametric dependence of a number of special points on the propagation curves. A procedure for achieving a balanced hybrid condition in the horn aperture is discussed following the proposal made by Bryant.     

A rectangular corrugated feed horn

This paper presents typical results of measurements made on a square corrugated horn and also one with a small rectangular aperture that was designed to generate an elliptical beam for either of two orthogonally polarized signals.     

Phase centers of horn antennas using Gaussian beam mode analysis

The power of Gaussian beam mode analysis to accurately describe the propagation of electromagnetic beams and the location of a horn antenna phase-center is illustrated. By way of example, the case of a compensated pyramidal horn fitted with fins to produce a less abruptly tapered E-plane field distribution is discussed, and the results obtained are compared with those from an alternative method published in the literature. Excellent agreement is found     

FDTD analysis of electromagnetic wave radiation from systemscontaining horn antennas

The application of the finite-difference time-domain (FDTD) method to various radiating structures is considered. These structures include two- and three-dimensional waveguides, flared horns, a two-dimensional parabolic reflector, and a two-dimensional hyperthermia application. Numerical results for the horns, waveguides, and parabolic reflectors are compared with results from using the method of moments (MM). The results for the hyperthermia application are shown as extensions of the previously validated models. This new application of the FDTD method is shown to be useful when other numerical or analytic methods cannot be applied     

An analysis of a two-dimensional dielectric covered corrugated antenna feed horn

The effect of placing a dielectric slab over a90degcorrugated feed horn is investigated. The feed horn is normally a circular waveguide with concentric grooves in the aperture plane. Here we simulate the90degfeed horn with a two-dimensional configuration which is a parallel-plate waveguidewith adjacent notches. The equivalence principle and modal analysis are used to formulate integral equations which are solved numerically by the method of moments. Numerical results for the input admittance are obtained with and without the corrugation and with and without the dielectric slab cover.     

Soft and hard horn antennas

Horn antennas with soft and hard boundaries are analyzed. A soft boundary which exists in classical hybrid-mode horns gives zero field intensity at the wall. A hard boundary corresponds to a uniform field distribution over the horn aperture. Soft and hard horn antennas are compared with respect to directivity, sidelobes, and beamwidth. The dependency between the edge taper directivity, and sidelobes is also calculated based on the solution to the spherical hybrid modes in a conical horn with arbitrary wall impedances. This makes it possible to study how to compromise between directivity and sidelobes. Also discussed is how the different wall impedances may be realized, and some preliminary experimental work on hard horns is presented     

Compact dual-profile corrugated circular waveguide horn

A new type of corrugated horn is presented. It is designed to have a dual-profile corrugation, yielding a more compact structure with respect to standard linear or sinusoidal profiled horns. It is also shown that the new design has some interesting features in terms of the phase centre location and its level of variation over the operating bandwidth     

Influence of horn length on radiation pattern of oblique-flare-angle corrugated horn

The influence of horn length on the radiation pattern of an oblique-flare-angle corrugated horn is described. Two experiments with a 110° horn are reported. These show that a horn with three slots has a radiation pattern which is essentially the same as that of a horn with five slots. It is also demonstrated that the innermost slot has a dominant effect on the pattern.     

Radiation characteristics of dielectric-loaded horn antennas

The radiation characteristics of electromagnetic horns loaded with curved transverse dielectric slabs and radial dielectric strips are investigated experimentally. It is shown that the axial directivity and halfpower beamwidth of horn antennas may be significantly improved with such schemes of dielectric loading.     

The phase center of horn antennas

The calculation of phase centers for rectangular and diagonal horns is presented. The calculation is based on a vector approach, by deriving the phase center from the expressions for the far field. Different expressions are derived for the phase center of theEandHplanes. The phase center for an arbitrary plane is calculated from theE-andH-plane phase centers. Graphs are presented showing the dependence of the phase centers on horn dimensions.     

New types of dielectric-loaded horn antennas

This paper presents low-loss dielectric loading techniques for improving some of the radiation characteristics of H-plane horn antennas. Specifically, the paper reports experimental results over new horns loaded with dielectric in the transverse and longitudinal planes with and without air gaps between the dielectric layers or between the dielectric and metallic walls. Sample results are presented showing improvements in the beam width, axial gain, input voltage standing wave ratio (VSWR) at the expense of new or increased side lobe level at some frequencies within the passband. Results are also presented to show that the main beam of a novel dielectric-loaded horn can almost be scanned from one wall of the horn to the other in synchronism with frequency sweep within the passband. Finally, a line-of-sight portable communication device employing the characteristics of dielectric-loaded horn antennas is proposed for further research and development.     

Comprehensive analysis for E-plane of horn antennas by edge diffraction theory

Edge diffraction theory is used in analyzing the radiation characteristics of typical horn antennas. The far-sidelobe and backlobe radiation has been solved without employing field equivalence principles which are impractical in the problem. A corner reflector with a magnetic line source located at the vertex is proposed as a model for the principalE-plane radiation of horn antennas. A complete pattern, including multiple interactions and images of induced line sources, is obtained in infinite series form. Diffraction mechanisms are used for appropriate approximations in the computations. The computed patterns are in excellent agreement with measured patterns of typical horn antennas. Radiation intensity of the backlobe relative to mainlobe intensity is obtained as a back-to-front ratio and plotted as a function of antenna dimensions.     

A rectangular horn of four corrugated plates

We describe a rectangular horn with radiation characteristics similar to those commonly obtained with corrugated horns of circular aperture. The horn described here consists of four identical plates, whose grooves can be obtained (straightforwardly and accurately) by numerical machining. Measurements from 8.7 to 12.2 GHz show that the horn aperture illumination is given to a good approximation by the distribution cos (alpha x) cos (gamma y) in agreement with a previous asymptotic theory. An advantage of this horn over a circular horn is that different beamwidths are obtainable in the two principal planes.     

Investigation of a 90° corrugated horn

Wide-angle corrugated horns have found important practical applications as feeds for front-fed reflector antennas when low levels of crosspolarisation are required. A theoretical study has been carried out on the 90° corrugated horn for a structure possessing an 'arbitrary, but finite, number of corrugations. Computed and measured results are shown to be in good agreement for a horn possessing three annular slots.     

Design and analysis of quasi-integrated horn antennas formillimeter and submillimeter-wave applications

The authors present a systematic process for the design of multimode quasi-integrated horn antennas, and provide a full range of practical antenna designs for millimeter- and submillimeter-wave applications. The design methodology is based on the Gaussian beam approach and the structures are optimized for achieving maximum fundamental Gaussian coupling efficiency. For this purpose, a hybrid technique is used in which the integrated part of the antennas is treated using full-wave analysis, whereas the machined part is treated using an approximate model. This results in a simple and efficient design process. The design procedure has been applied to the design of 20-, 23-, and 25-dB quasi-integrated horn antennas, all with a Gaussian coupling efficiency exceeding 97%. The designed antennas have been tested and characterized using both full-wave analysis and 91/370-GHz measurements. The quasi-integrated horn antennas are also examined as feed elements for Cassegrain antenna systems and are proved to be comparable to the traditional machined corrugated horn feeds