Diffraction from rotationally symmetric ensembles of open and closed arbitrarily shaped screens

This paper analyses scalar scattering and diffraction from ensembles of coaxial axi-symmetric closed or open screens that are arbitrarily shaped. Plane wave and complex point source excitations are examined in the frequency domain by the semi-analytic Method of Regularisation. The Dirichlet boundary value problem for the Helmholtz equation is reduced analytically to a well-conditioned coupled infinite system of algebraic equations. This system is then effectively solved by a truncation method with any pre-specified accuracy, strictly depending on the truncation number. Applications related to plane wave excitation include accurate studies of coupled cavity resonators, of open cavities with insertions and of configurations where targets lie in the shadow zone. Our investigation employing beam-like excitation focuses on the accurate analysis of a front-fed parabolic reflector antenna. The tapered illumination is simulated by a complex-point source, supported by a back plate. The maximum permissible extent of the supporting back plate that does not unduly compromise the operation of the reflector antenna is determined. Numerical results based on the solution and related field plots are presented and discussed.