A multi-turn, circularly polarized, radiating-line antenna

The authors report on the development and experimental verification of a multiturn radiating-line antenna. The antenna consists of a single-strip conductor formed into overlying spiral arms. Several antennas were built to test the influence of the various parameters. The bandwidth of the multiturn, radiating-line antenna was defined after considering the input impedance, the relative power absorbed, the polarization, and the squint of the beam. At low frequencies the limiting factor is the relatively small amount of power that can be radiated. At high frequencies, the bandwidth is limited by the degradation of the axial ratio of the polarization ellipse. The circular polarization bandwidth is usually defined as the frequency range for which the axial ratio is less than 3 dB. This criterion was adopted to define the upper frequency of operation. Accordingly, the antenna considered exhibits 46% bandwidth.<>