Plane wave incidence to a cylindrical frequency selective surface comprising of metal strips

Scatterings from circular cylindrical structures comprising of free-standing ordielectric shell backed metal strips are considered. When formulating the problem,the scattered waves are written as infinite sums of cylindrical Floquet modes withunknown weighting coefficients. The weighting coefficients are then determined byusing boundary conditions appropriate for the problem. Numerical results areobtained by applying the Moment method (MM) techniques whereby entire domainsinusoidal basis functions are used. The infinite sums appearing in MM solutions arefound to be slowly convergent. When solving the problem by a MM technique, theinfinite sums should be handled properly in order to circumvent slow convergencedifficulties. One approach in such a case is to use sub-domain basis functions inconjunction with a conjugate gradient fast Fourier transform method. Anotherapproach is to use entire-domain basis functions together with a convergenceacceleration method. Here, we follow the second approach and give an appropriateconvergence acceleration method. It is shown that the resulting infinite sums of theMM solutions can be very efficiently computed by employing a new convergenceacceleration technique based on Kummer?s method.Results reveal that the thickness of the dielectric shell strongly affects thescattering properties of conducting strips. Moreover, resonances are detected at somespecific frequencies where the structure becomes almost invisible to an observer.iiiSuch properties of cylindrical structures may be very useful in radar applications orantenna applications.Keywords: Cylindrical Frequency Selective Surface, Cylindrical Structures,Cylindrical Floquet Modes, Convergence Acceleration, Kummer?s Method,Scattering, Radar Cross Section.iv