Analysis of linear waveguide arrays in a flare

Antennas consisting of linear arrays of waveguide apertures in a flare are commonly used either as feeds for cylindrical reflectors or as direct radiators. Usually, only a single linear polarisation is employed, but there can be applications in which both dual linear or circular polarisation are required. It is then desirable to corrugate the inner walls of the flare longitudinally to maintain a similar amplitude distribution for both linear polarisation. Matching irises may be incorporated in the input waveguides. We have developed a mode matching technique based on a hybrid Floquet/waveguide mode expansion of the field in the flare to analyse such structures accurately