A dipole-fed multi-band spiral antenna

A novel structure of multi-polarization spiral antennas is presented. The spiral antenna radiates not only linearly polarized waves but also circularly polarized waves simultaneously without phase shifters. In this paper, the way to tune the antenna into three bands, GPS and two mobile phone bands, is delineated. The return-loss characteristics as regards various lengths of the appropriate elements that can control utilized frequencies of the antenna are discussed to show that the antenna can be tuned into multi-bands. The return-loss and radiation patterns are delineated by comparing simulation results and measurement results. These results show that the antenna radiates good circularly polarized waves as well as good linearly polarized waves at a GPS and mobile phone bands, respectively.