Gain of corrugated conical horns

The absolute gain of a corrugated horn which is designed as a 100-GHz gain standard for the Crawford Hill 7-Meter offset reflector has been calculated and measured. The measured gain is determined from "three horn" transmission measurements. The other two horns are a TRG Model W869 corrugated horn and a dual mode horn. Correction factors were computed from the near field power transmission formula. The measured gain of the gain standard is30.8 pm 0.16 dB. Comparison between measured and calculated gains indicate very low ohmic loss in a corrugated horn. The condition of maximum gain for a given length has been found to be a half wavelength phase deviation in the horn aperture. Calculated gain data as well as near field correction factors for two identical corrugated conical horns are given here as reference information.     

Design of profiled corrugated horns

The design principles used to realize smoothly profiled corrugated horns are described. The smooth profiling causes power to be converted to higher order HE₁₂ modes which radiate to produce high sidelobes in the copolarization patterns. A computer-aided spherical modal-matching technique is used to study the higher-order mode conversion. The results show good agreement with measurements. A profiled horn using a series of discrete conical sections is proposed to eliminate most of the mode conversion. A horn designed in this way is presented and shown to possess improved performance characteristics in comparison to a smoothly profiled design     

Bandwidth properties of corrugated conical horns

It is shown that the aperture fields of circumferentially corrugated conical horns remain virtually unchanged over a very wide frequency range, and that the bandwidth improves as the length of the horn is increased. The theory is applicable over a large range of flare angles.     

Near-field radiation characteristics of corrugated horns

The amplitude and phase patterns of corrugated feed horns are predicted in the near-field region by means of a spherical-mode-expansion method which has been previously applied only in the far field. Excellent agreement has been observed with experimental patterns, and typical results for horns with flare semiangles of 12° and 70° are described.     

Design of wide-band compact corrugated horns

It is shown that a specially profiled corrugated horn with a ring-loaded input converter section is capable of operating over bandwidth ratios of up to 2.4: 1. The cross polarization across the band is relatively low, and the change in beamwidth and phase-center position with frequency is acceptable for many applications. This "compact" horn is significantly smaller than the conventional wide-band corrugated horn, and is particularly recommended as a feed in a dual-reflector antenna where space is limited.     

Simulation of corrugated horns and exciters for circular corrugated waveguides

A method is proposed for simulating the problem of radiation from a finite-length corrugated horn joined with a regular corrugated waveguide. Obtained with the help of the factorization method, a solution to the problem of radiation from the open end of a circular waveguide is applied to formulate the conditions of radiation from the horn.     

Lenses for wideband corrugated conical horns

A dielectric lens, designed to be fed by a wide-angle corrugated conical horn, is described. The radiation pattern of the horn-lens combination is similar to that of a much longer conical horn while retaining wideband characteristics.     

Diffraction by wide-flare-angle corrugated conical horns

Expressions for the diffracted far field of a wide-flare-angle corrugated conical horn (operating on the HE11 mode) have been obtained making use of a simpler expression for the aperture field. Expressions for the radiation pattern and gain reduce to a closed form when the flare (semivertical) angle is less than 30°. The theoretical results are in close agreement with experiment.     

Hybrid modes in corrugated conical horns

A simpler solution for spherical hybrid modes in corrugated conical horns has been shown to have a deviation from the rigorous solution of less than 0.7 dB for the case considered by Clarricoats. Expressions for the radiation pattern and gain of such a horn with small flare angle have been obtained under balanced hybrid conditions.     

Design of corrugated horns: a primer

Typical example of horn is shown where the inside wall is manufactured in a succession of slots and "teeth". The purpose of the corrugated surface is to provide the means to support the propagation of hybrid modes within the horn. Hybrid modes are basically a combination of TE and TM modes. Some basic information for the inexperienced horn designer to get started in designing their corrugated horn is provided. The class of circularly symmetrical corrugated horns and the parameters in designing are considered. As an example a standard Ku-band operation from a typical Earth station is also considered.     

VSWR properties of E-plane dihedral corrugated horns

A moment method solution is used to evaluate the VSWR of dihedral corrugated horns in terms of the various contributors. Knowledge gleaned in this fashion is then used to control these reflections, and in turn reduce the horn VSWR. Use of an appropriate curved horn waveguide geometry in conjunction with a tapered corrugation input yields a very small VSWR over a reasonable band.     

Broadbanding of corrugated conical horns by means of the ring-loaded corrugated waveguide structure

Broadbanding of corrugated conical horns is investigated with the ring-loaded corrugated circular waveguide (RCWG) structure devised by the authors. The useful frequency bandwidth in which the corrugated horn is effective for the improvement of antenna properties is limited by the frequency characteristics of the horn-aperture field and input VSWR of the horn. By the precise analysis of the RCWG, the maximum frequency range in which the desirable field is obtained is much wider than that in the conventional corrugated circular waveguide, and is achieved almost independent of ring thickness, when ring width is about 20 percent of slot depth. The characteristic impedance of the RCWG is nearly equal to that of the homogeneous circular waveguide when ring thickness becomes large. Therefore, a good transformer between the RCWG and the homogeneous circular waveguide is achieved by increasing ring thickness from the RCWG toward the homogeneous waveguide. From the above investigations, it is found that in the ring-loaded corrugated horn, the useful bandwidth is 1.35 times broader than that in the conventional corrugated horn. The theoretical results are verified by the experimental results.     

Propagation and radiation characteristics of corrugated horns

A new method for predicting the radiation pattern of a corrugated horn is described which is especially relevant to horns with oblique semi-flare angles. Experimental and theoretical results are compared for a horn with a semi-flare angle of 110°. The solution of the characteristic equation is described in the throat region of the horn, and results are presented for the four lowest modes of propagation with 30° < ?1 < 160°.     

Shielding effectiveness of corrugations in corrugated horns

A moment-method solution is used to obtain new design data for corrugated horns. The current density on the walls of corrugated dihedral horns is evaluated as a function of such corrugation parameters as the tooth density, and the ratio of the gap to the period (of the corrugations). The shielding effectiveness or the capability of the corrugations to prevent the edge of the horn from being illuminated is discussed, as is the question of the efficiency of corrugated horns.     

A hybrid technique for analyzing corrugated and noncorrugated rectangular horns

A hybrid technique is proposed to solve the entire problem of corrugated and noncorrugated rectangular horns without the usual approximations. The horn antenna is simulated by a multistepped waveguide structure radiating into half-space. The procedure is composed of three steps. First, assuming the horn to be terminated by infinite metallic flange, the aperture problem is accurately solved by a hybrid modal-spectral method (HMSM). Second, the modal analysis (MA) method and scattering matrix concept of waveguide discontinuities are employed to solve the transverse multidiscontinuity problems. Finally, the two methods are combined (MA-HMSM) to solve the entire problem of the horn antenna. The proposed technique allows to obtain not only the radiation patterns, but also the reflection and near-field characteristics of the horn, without any restriction on the geometry (semiflare angles, profiled horn contours, corrugations). A good agreement between theoretical predictions and experimental results has been obtained for several horns.     

Pattern shaping with hybrid mode corrugated horns

Hybrid modes in a square corrugated waveguide are investigated, and a technique of combining several modes for pattern shaping is described. The mode amplitudes are calculated from a known throat excitation and used to compute radiation patterns. One horn was designed, constructed, and tested. The theoretical patterns were in good agreement with experimental data.     

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.     

Eigenvalues of spherical surface-wave modes in corrugated conical horns

An analytically simple and sufficiently accurate asymptotic solution for the eigenvalues of spherical surface waves in corrugated conical horns is described. An iterative procedure for numerical evaluation of the exact eigenvalues associated with the surface waves of the lowest order is presented here.     

Design of conical corrugated feed horns for wide-bandhigh-frequency applications

This paper presents a new analytical procedure for the design of the conical corrugated feed horns used in the millimeter and submillimeter wavelength range, which could achieve wide-band single-mode operation and wide-band, low return-loss impedance matching simultaneously. A test model of the feed horn designed using this procedure displayed excellent performance, and agreed well with the theoretical predictions     

Characterization of corrugated feed horns at 216 and 300 GHz

We present measurements of the near-field beam profiles of two corrugated feed horns with center frequencies of 216 and 300 GHz. Both co-polar and cross-polar components of the electric field have been probed across the operation band of the horns. A full-wave numerical near-field transformation, based on a vector Kirchhoff integral, is implemented to transform the measured field to the horn aperture for a comparison with the ideal aperture field. From the overlap integral of the transformed and the ideal field, we conclude that the field radiated by these horns is the HE₁₁ mode, to a purity of better than 99%.