A method of determing the optimum phase center location of antenna feeds employed in reflector systems is described. The phase center of the wide-band scalar horn used in prime-focus and dual-reflector antennas has been calculated numerically and the results are discussed.

Phase center calculations of reflector antenna feeds

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 the H -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.

GTD analysis of a hyperboloidal subreflector with conical flange attachment

A generalized method for analysis of antenna near field is presented which relies on both additivity of radiation field of discrete antenna elements and sampling method of an aperture field. It has advantages of implementing easily and saving the computing time and storage. Some results are compared with published data, and the agreement is good. It can be widely used in EMC prediction.

A generalized algorithm for antenna near-field computation in EMC prediction

Phase center of reflector antenna feeds

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].

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

A novel technique for the analysis of the principal plane near-field patterns of conical and corrugated conical horns excited in the dominant mode based on the uniform geometrical theory of diffraction (UGTD) [1], [2] is presented. Numerical computations of the near-field amplitude patterns of a few typical conical and corrugated conical horns based on the GTD technique detailed here correlate well with the measured patterns, justifying the validity of the analysis presented.

K. Rao

Papers

GTD analysis of the near-field patterns of conical and corrugated conical horns