LAUSR

Abstract This paper presents an ultrawideband (UWB) circularly polarized (CP) two-arm Archimedean spiral antenna with unidirectional radiation patterns. The antenna is directly fed by a 50-Ω coaxial cable and reflected by a circular cavity. The proposed design is able to exhibit high gain, high radiation efficiency as well as UWB CP operation by properly choosing the reflector’s dimensions and the spiral’s growth rate. This overcomes the critical drawback of the other reported UWB CP spiral antennas in literature, which always suffer from poor performance in the lower operating frequencies. The measured reflection coefficient and axial-ratio show a good performance over a frequency band 6–16 GHz. Furthermore, the values for gain and radiation efficiency of the proposed design are always better than 5.2 dBic and 85%, respectively.