Radiation Characteristic of Aperture-Limited Dominant Beam Mode of Lens-Type Beam Waveguide

摘要

The radiation characteristic of the dominant beam mode of a lens-type beam waveguide is discussed; the assumption is made that this mode illuminates a circular aperture in a metallic screen. Radiation patterns are presented for various aperture radii and various distances between the aperture plane and the last lens of the guide. The exact field distribution of the beam mode can be determined without extensive computations only at the location of the lenses, and this only for confocal guides. In all other cases, the Gaussian approximation of the mode function was used for calculation of the radiation characteristics. In the special case where the exact field distribution is known, the characteristics derived from this distribution have been compared with those obtained using the corresponding Gaussian approximation. For sufficiently large lens apertures the 3 dB beam width of the actual and the approximate patterns is nearly the same, while the side lobe level of the two patterns shows differences depending on the aperture radius. (Author)