A Dual Circularly Polarized Co-Aperture Yagi Antenna Based on Counter-Wound Helix

A dual circularly polarized co-aperture Yagi antenna is proposed. It consists of two orthogonal 3-element Yagi with left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP), respectively. Each Yagi is composed of three five-segment counter-wound helices, one of which is driven element and the other two are employed as parasitic elements. Each helical element has five segments of helical wires, and every two connected helical wires have different directions of rotation. By carefully choosing the parameters of the helices, a pattern with circular polarization is achieved. An endfire beam is then obtained by optimizing the parameters of the Yagi, such as the spacing of element. The dual circular polarization is achieved by using two orthogonal single Yagi antennas forming a crossed shaped. Simulation results show that a dual circular polarization is obtained with both gains better than 5 dBic.