Line source radiation in the presence of slotted cylinders

Axially slotted circular cylinders possess interesting scattering characteristics, the most notable of which is a reduction in their lowest natural resonant frequency as compared to that of a closed cylinder. The authors examine two other canonical shapes, cylinders with square and triangular cross-sections, which have been found to exhibit similar characteristics. Detailed results at two frequencies, one corresponding to the maximum radiation resistance and the other to maximum directivity, are shown. In all three cases (slotted circular cylinder, slotted square cylinder, and slotted equilateral triangular cylinder), the phase of the induced current distribution becomes nearly uniform at the frequency corresponding to maximum directivity. As expected, the amplitude of the current distribution goes through a minimum. Whereas the cylindrical cross-section is optimum in terms of electrical dimensions, for the same slot opening-to-perimeter ratio, the triangular cylinder retains its directive characteristics over a wider frequency range.<>