Multiband two arm slot sinuous antenna

The traditional sinuous antenna is a center-fed, broadband, self-complementary, four arm structure composed of arcs and bends. The frequency operation limits are determined by its inner and outer diameters. The proposed design is different from the traditional sinuous antenna in that it is a two arm rather than a four arm structure and that it is excited in a slot-mode rather than in a wire or printed mode. Very little, if any, research has been performed on two-arm sinuous antenna geometry. When excited with 180/spl deg/ phase progression between both input ports, the antenna demonstrates multiband behavior with maximum gain at broadside, and good axial ratio, omnidirectionality, and return loss at most bands. Multiband performance of a two-arm slot sinuous antenna is demonstrated. Bands occur at one lambda circumferential rings about the geometrical center of the antenna. The positions of these rings, corresponding to frequency bands of operation, can be tuned by varying antenna size and/or sinuous growth rate. At these bands, the good axial ratio (<4 dB) and low return loss (<-10 dB) are demonstrated. It is also shown that having termination resistors across the open end significantly improves axial ratio for the lowest resonant band. A more rigorous design of the feeding region as well as the use of a conical cavity could improve the antenna performance.