Comparison of blockage widths of ideally hard cylinders of different cross-sectional shapes

We have computed the equivalent blockage width of ideally hard cylinders of different cross sections. We have shown that the oblong cross section is best when the physical width is larger than about 0.2square, whereas for narrower cross-sections the transverse thin rectangular cross-section is best. The latter can be strengthened by a star-shaped cross section, without significant change in the blockage width. The latter was found as a result of numerical optimization. The optimized oblong shape is explained by a smooth transition of the waves past the cylinder, which is facilitated by the GO characteristics of the hard surface [8]. The thin rectangular cross section is explained as a quasi-static solution. The cross-section is so narrow in terms of wavelengths that transverse currents cannot be induced. The star-shaped cross-section works like the transverse rectangular cross-section, because the orthogonal rectangular part making up the two other arms of the star are invisible to the wave because of their small thickness. It must be emphasized that we have treated ideally hard cylinders. This makes the results valid for metal cylinders and TE-case. The performance for TM-case depends on the realization of the PMC surface, but the results can be seen as typical performance at the center frequency. The bandwidth will normally be small, but can be up to 20-30% when the artificial magnetic conductor is realized by dielectric coatings.