The performance of an iris-loaded planar phased-array antenna of rectangular waveguides with an external dielectric sheet

A new method for calculating the performance of an iris-loaded planar phased-array antenna of rectangular waveguides is presented. The method is based upon the expansion of the tangential electric aperture field in terms of judiciously chosen functions. Also, the influence of a dielectric sheet in front of an antenna the apertures of which are loaded with inductive irises is investigated. In the experiments, a sheet with a low relative permittivity (epsilon_{r} = 2.3orepsilon_{r} = 3.5) is spaced in front of a space-fed planar antenna of some 850 radiating elements, and the total transmitted power of the antenna is measured as a function of frequency and scan angle. The results indicate, that both in theory and in practice, an excellent match can be achieved with a polythene sheet (epsilon_{r} = 2.3) or a Perspex sheet (epsilon_{r} = 3.5).