Performance Analysis of a Quadrifilar Helix Antenna Above the Ground Plane

Design and performance evaluation of a modified quadrifilar helix antenna (QHA) above various terrains are investigated utilizing the method of moments (MoM). In particular, antenna performance above "average ground" plane with epsivtau=13 and sigma=5 mS/m and "extremely poor" ground that is common to heavy industrial cities having epsivtau=3 and sigma=0.1 mS/m is first considered as a base line. Two extreme cases of antenna orientation above the ground plane are considered and antenna modification method is presented to reduce the ground reflection effect. Simulated axial ratio of less than 0.3 dB is achieved along the antenna axis over 20% bandwidth operating in the cellular frequency band