Application of rectangular and elliptical dielcore feed horns toelliptical reflector antennas

The pattern characteristics of elliptical reflector antennas are investigated when they are fed by rectangular and elliptical horns partially filled with a dielectric. The bandwidth characteristics of these dielcore horns are superior to those of their corrugated horn counterparts. Representative reflector patterns are computed to properly demonstrate the utility of these feeds for reflector antennas with elliptical apertures. This reflector antenna exhibits high efficiency and low cross polarization, and may be suitable for radar and satellite antenna applications. The antenna configuration may become useful in relatively small antennas where more than 10% cross-polar bandwidth is required. The efficient dielcore horns may also be used as feeds for elliptical nonshaped dual-reflector antennas     

On refining the name of one type of horn antennas

Advanced communications systems operating in the microwave band involve a wide use of horn antennas of different modifications. Horn antennas are applied as separate antennas, as feeds of reflectors, and elements of antenna arrays. However, the horn antennas most frequently used in practice and conventionally called pyramidal horns, in the view of the authors can be more accurately called wedge-shaped or wedge-like horn antennas: wedge is a more general variant of polyhedron, which is the basic component for designing the geometry of such horn antennas.     

Radiation patterns of metal and dielectric wall diagonal horn antennas

The radiation patterns and gain of dielectric wall diagonal horn antennas of various thicknesses (0.15cm and 0.32 cm) and dielectric constants (? = 2.54, 2.56 and 3.03) have been experimentally studied and compared with a metal diagonal horn antenna having the same aperture at 9.418 GHz. Radiation patterns of these dielectric horn antennas when used as square horns are also presented and compared with a similar metal horn. The use and applicability of dielectric horn antennas is discussed.     

Corrugated horns

The corrugated horn has become the preferred choice of antenna for use in high-performance microwave reflector antennas for communications, radar and remote sensing. The principles and attributes of corrugated horns are explained. The analysis, design and manufacturing techniques and types of horns in use are briefly discussed     

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     

Analysis of pyramidal horn antennas using moment methods

A hybrid numerical technique is developed for electrically large pyramidal horn antennas radiating in free space. A stepped-waveguide method is used to analyze the interior surfaces of the horn transition. The electric field integral equation (EFIE) is employed on the outer surfaces of the pyramidal horn including the radiating aperture. Meanwhile, the magnetic field integral equation (MFIE) is used on the aperture to relate the aperture fields and those in the horn transition The resultant hybrid field integral equation (HFIE) is solved numerically by the method of moments. This formulation is both accurate and numerically stable so that high-gain microwave pyramidal horns can be analyzed rigorously. Far-field radiation patterns, both computed and measured, are presented for three electrically-large X-band horn antennas. The comparisons demonstrate that this method is accurate enough to predict the fine pattern structure at wide angles and in the back region. Computed far-field patterns and aperture field distributions of two smaller X-band horns are also presented along with a discussion on the validity of the approximate aperture field distributions routinely used in the analysis and design of pyramidal horns     

An offset reflector antenna with low sidelobes

The corrugated conical horn is considered to be an ideal feed for low sidelobe reflector antennas because of its unique characteristics. Analysis is carried out to show that low flare horns are preferred over high flare horns to give rise to low sidelobe performance for a given offset reflector antenna system.     

Design of wide-band corrugated conical horns for Cassegrain antennas

Design procedures based on extensive theoretical and experimental investigations are given for hybrid-mode corrugated conical horns having near-constant beamwidth, low cross-polarized sidelobes and low reflection for continuous bandwidths up to 2.1:1. The design techniques are applicable for horn flare semi-angles to about30deg, which includes most feed horns in dual-reflector antennas.     

Ultra-wideband horn antennas with a considerable difference in radiation pattern width in <Emphasis Type="Italic">E</Emphasis>- and <Emphasis Type="Italic">H</Emphasis>-planes

The paper presents results of theoretical and experimental investigation of ultra-wideband horn antennas with a rectangular aperture and input formed by a symmetric H-waveguide. The antennas show a considerable difference in their radiation pattern widths in the E-and H-planes, and good matching properties in a range of frequencies from 1 to 10 GHz. The required difference between radiation patterns of the antennas is attained by proper selection of horns’ geometry and application of a diverging dielectric lens in each horn. Optimal profiles of the horn antenna generatrix and of the dielectric lens placed inside are determined. Reliability of results of the theoretical analysis is confirmed by testing the designed prototypes of the ultra-wideband H-sectorial and E-sectorial horns.     

Aperture efficiencies of large axisymmetric reflector antennas fedby conical horns

It is shown how the radiation patterns of conical horns can be understood in terms of Laguerre-Gaussian beam modes. This approach provides a simple method for calculating the horn radiation pattern as it propagates through a multielement optical system consisting of lenses or offset mirrors with large focal ratio and/or a small angle of incidence, and can be used in quantitatively determining aperture efficiencies for systems where conical horns are coupled to antennas via tertiary optics. The resulting aperture efficiency results and a practical quasioptical system fed by a conical horn are discussed     

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     

Design of short e-plane sectoral horns

A method combining the `generalised telegraphist's equations? with a mode-matching technique is proposed well suited for the calculation of short horn antennas. Curves are given for the optimum flare angle, gain and reflection coefficient of a plane sectoral horn excited in the TEM mode. It is shown, that for short horns the aperture-throat interactions cannot be neglected.     

Broad-band elliptical beamshape horns with low cross polarization

Horn antennas with an elliptical beam and low cross polarization are discussed. A new class of elliptical-beamshape horns has been investigated. The horns are based on the dielectric core approach, using a dielectric core inside a smooth-walled horn. Horns with rectangular as well as elliptical cross sections have been studied. Experiments show that they have considerably larger cross-polar bandwidth than that obtained from corrugated horns with an elliptical beam. They are also potentially much cheaper to manufacture     

Optimizing multimode horn feed arrays for offset reflector antennasusing a constrained minimization algorithm to reduce cross polarization

This letter presents an algorithm for suppressing the cross polarization of single offset reflector antennas illuminated by a cluster of multimode horn feeds using a constrained minimization routine. The design variables are the mode ratios for the higher order modes excited in the feeds relative to the dominant TE₁₁ mode. The goal is to systematically determine the optimum mode ratios such that the overall crosspole performance of the reflector antenna improves relative to the single TE₁₁ mode excitation. The multimode horns considered are Potter-type (dual mode) horns and trimode horns     

A Multilayer Negative-Refractive-Index Transmission-Line (NRI-TL) Metamaterial Free-Space Lens at X-Band

A volumetric free-space negative-refractive-index (NRI) transmission-line (TL) metamaterial lens is described that employs fully printed interdigitated capacitors and meandered inductors designed to exhibit NRI properties at X-band (8-12 GHz). The volumetric topology is realized in a layer-by-layer fashion without any vias, which facilitates easy and rapid fabrication. The fabricated lens was tested for its transmission and dispersion properties using a free-space X-band measurement system consisting of an Agilent network analyzer, standard gain horn antennas, and Rexolite dielectric lenses fabricated in-house, and showed good correspondence with simulations. The focusing ability of the multilayer NRI-TL lens was also verified using a free-space field probing system based on small shielded-loop antennas affixed to a computer-controlled xyz-translator apparatus. Arguably, these results represent the first experimental evidence of coupling between TL-based metamaterials and sources in free space.     

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.     

毫米波天线

本文评述了适用于毫米波和亚毫米波的天线设计。该频段在通信、雷达和遥感方面的应用正在迅速发展,并且需要高性能天线。许多新颖的设计都致力于毫米波特性的开发利用。较短的波长意味着更严格的公差。从而要求更精密、更有效的反射面和馈源喇叭。本文综述了反射面天线、透镜天线、喇叭天线、平面天线、行波天线和集成天线。     

A review of the early developments of circular-aperture hybrid-mode corrugated horns

The simultaneous but independent development in the United States and Australia of circular-aperture corrugated horns in the early 1960's is reviewed. The features of this development include the wide flare-angle corrugated "scalar" horn and the characteristics of focal-region fields of reflector antennas and the single- and multimode cylindrical corrugated horns necessary to feed them.     

Optimization of Broadband Smooth-Wall Circular Horn Antennas

This paper presents the optimization and characterization of broadband circular horn antennas with smooth walls. These antennas are simpler and easier to manufacture than corrugated horns. They work by converting the incoming fundamental mode to a mode mixture, whose total field corresponds to a Gaussian beam pattern at the aperture. The geometry of the horn is found by an optimization algorithm. While smooth-wall horn antennas have been designed for many years, they are inherently band limited because they rely on a correct multimode interference in the aperture to match the total field to a Gaussian distribution. The presented method achieves significantly larger bandwidths by allowing the Gaussian beam parameters, and thus the required mode spectrum in the aperture, to vary with the frequency. Together with an appropriate mirror optics, a receiver system with a bandwidth of more than 3 octaves could be realized.     

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.