Characteristics of a broadband printed quadrifilar helical antenna employing a novel compact feeding circuit

A broadband printed quadrifilar helical antenna employing a novel compact feeding circuit is proposed in this paper. Good results have been obtained in simulation for the quadrifilar antenna alone. To feed this antenna, a circuit based on an aperture-coupled transition and including two 90deg surface mount hybrids has been designed. The measured return loss of this circuit is greater than 12 dB between 1.06 and 1.64 GHz, the maximum output magnitude imbalance is 0.5 dB, and the maximum output phase imbalance is 3deg over the same bandwidth. Simulations have been carried out to evaluate the effect of the aperture in the ground plane on the antenna performance. The simulated active return loss has been found to be equal to or greater than 10 dB and the gain varies between -0.5 and 3.5 dBc from 1.27 to 1.63 GHz. The HPBW is 144deg, and the cross-polarization rejection is greater than 14 dB over the HPBW. At 1.4 GHz, the AR is lower than 3.3 dB over the HPBW. A 16-dB back-radiation level of the LHCP has been noticed in this case at 1.4 GHz.