A circularly polarized UHF antenna at 550-700 MHz

The paper reports on a design of a low-cost circularly polarized turnstile bowtie antenna in the low UHF band (550 MHz-700 MHz) that has a wide impedance and polarization bandwidth (in excess of 20% at zenith assuming 3 dB axial ratio). In addition, the antenna should have a near omnidirectional RHCP radiation pattern in the upper hemisphere and a good front to back gain ratio.