Parametric study of short backfire antennas with different cavity profiles

A number of high aperture efficiency waveguide fed horn arrays have been investigated at millimetre wave frequencies for civil application. Short backfire antennas are a low profile alternative to horns, having a height of about 0.5/spl lambda//sub 0/, as opposed to several wavelengths. A large scale, dual polarised, waveguide fed array of short backfire antennas (SBA) has been proposed for DBS television reception (about 12 GHz). Such structurally robust and readily die cast arrays are also of interest for upperband MMDS, LMCS and LMDS subscriber antenna (25.35-31.3 GHz). However, waveguide fed SBAs are not well understood and have only been studied for a few distinct cavity diameters and depths. Also, a number of gain enhancement techniques have been trialed, but this work has also been sketchy. There is, thus, a need for a wide-ranging parametric study of SBAs before arraying can be considered, and a modern numerical tool such as Ansoft HFSS(TM) ver. 6.0 would be applicable. As an initial study, 5 different circularly symmetric cavity profiles fed by a rectangular waveguide were investigated across a range of diameters.