GTD analysis of the E-plane patterns of conical horns

An analytical procedure for predicting accurately theE-plane patterns of conical horns with moderate aperture widths (ka < 10), based on uniform geometrical theory of diffraction (UGTD) and supported by measured data, is presented. This analysis predicts theE-plane patterns more accurately (over the main beam) than the one presented earlier.     

A correction to the available formula for the GTD near-field patterns of conical horns

An error in the geometrical theory of diffraction (GTD) near-field analysis of a conical horn published earlier is pointed out. This error is corrected, and the correct expression for the near-field patterns for the conical horn is presented. Computations based on the corrected formulas correlate better with results based on measurement as well as aperture integration technique [4].     

GTD analysis of the radiation patterns of a shaped subreflector

A technique of analyzing the principal plane radiation patterns of a subreflector shaped using the method enunciated by Collins [1] has been presented. The analysis is based on the uniform geometrical theory of diffraction (UGTD) [2], and a simplified procedure has been adopted in the determination of the principal plane radii of curvature of the subreflector. The numerical results obtained based on UGTD correlate well with those obtained using the method of physical optics (PO).     

GTD analysis of the radiation patterns of a prime focus paraboloid with shroud

The uniform geometrical theory of diffraction (UGTD) is employed to analyze the far-field radiation patterns of a prime focus paraboloid with a cylindrical shroud. The blockage of the aperture illumination of the dish by the gooseneck and the primary feed is also taken into account in the analysis. Far-field radiation patterns (for0degleqTheta leq 180deg), calculated for a typical prime focus paraboloid with 2 m aperture diameter, designed and fabricated, are compared with the experimentally derived patterns at 8.8 GHz in theE- andH-planes. There is a satisfactory agreement between the two results.     

GTD analysis of a hyperboloidal subreflector with conical flange attachment

A geometrical theory of diffraction (GTD) analysis of the principal plane far-field radiation patterns of a hyperboloidal subreflector with a conical flange attachment (HWF) fed by a primary feed located at its focus is presented. While using the uniform geometrical theory of diffraction (UGTD) for evaluating the nonaxial fields, the method of equivalent currents is used in the axial region. In this paper, both the diffraction by the wedge formed between the hyperboloid and the conical flange and the diffraction by the edge of the flange are considered. While considering the diffraction by the edge due to the diffracted ray from the wedge in theH-plane, the slope diffraction technique has been used. The computed diffracted farfields of a typical HWF illuminated by a high performance primary feed shows good agreement with the available measured data and with the results based on the method of physical optics (PO). The sharp cutoff and the low spillover characteristics of the HWF are highlighted by comparing its radiation pattern with that of a hyperboloid without a flange. Further, the effects of the different parameters of the HWF on its radiation pattern are also studied and plotted, so that these results can be utilized in the design of the HWF for a specific requirement.     

Complex radiation patterns of dual mode pyramidal horns

The radiation patterns of the dual mode horn and its related performance are influenced by the phase difference between component modes at the horn aperture and the phase distribution associated with the horn flare angle. Both effects are shown to deteriorate beam symmetry and increase sidelobe levels. Radiation pattern functions and fractional power distributions associated with the dual mode pyramidal horn are illustrated for a range of mode and distribution phase errors.     

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.     

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.     

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.     

Paraboloidal-reflector illumination with conical scalar horns

This letter describes a systematic procedure for calculating the half flare angle of a conical scalar horn, illuminating a paraboloidal reflector of known f/D ratio, with a view to realising a prescribed sidelobe level for the secondary radiation.     

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.     

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.     

Radiation properties of 90° conical horns

A combination of the method of moments and the geometrical theory of diffraction (g.t.d.) is used to predict the radiation properties of 90° semiangle conical horns possessing a number of annular slots in the flange. Computed and measured results show good agreement, and a set of theoretical curves is given for application of the horn as a feed.     

Sum and tracking radiation patterns of a conical horn

The gain and the radiation patterns of a conical horn excited by a circular waveguide operating in theTE_{mn}andTM_{mn}modes are predicted. The expressions are rigorously derived by using the accurate calculation of the associated Legendre function with the real order and the integer degree.     

Radiation of conical horns excited in higher-order modes

Theoretical investigations carried out for the far-field-radiation-pattern prediction of conical horns excited in the spherical TMmn and TEmn modes are applied on the radiation-pattern analysis of TM01 and TE01 modes. The results, valid even for conical horns with large flare angles, provide an optimum horn design for a maximum gain slope near the boresight axis.     

Radiation from conical horns with large flare angles

Radiation patterns of conical horns with large flare angles excited in theTE_{11}mode are calculated from a simple solution for horn modes using the vector diffraction formula. Radiation patterns are expressed in closed form when the half-flare angle is less than30deg. Patterns obtained by experiment show close agreement with calculated results.     

GTD analysis of the near-field patterns of a prime-focus symmetric paraboloidal reflector antenna

The uniform geometrical theory of diffraction (UGTD) has been applied successfully to analyze the near-field patterns of a prime-focus paraboloid. In order to establish the validity of the analysis, near-field amplitude and phase patterns have been computed over the principal planes at several observation distances for a typical prime-focus paraboloid. These calculations compare very favorably with the corresponding results obtained numerically with the aid of Silver's near-field aperture integration formula.     

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     

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.