Effect of truncation shape against axial ratio of left-handed circularly polarized X-band antenna

In this paper, an effect of truncation shape of left-handed circularly polarized (LHCP) X-band antenna against its axial ratio is investigated. The antenna which is designed to have the center frequency of 8.2GHz and the axial ratio bandwidth of 400MHz is intended to be implemented for satellite communication. It is deployed on an NPC-H220A dielectric substrate with the dielectric constant of 2.17 and the thickness of 1.6mm. The structure of antenna is constructed of two layer dielectric substrates in which the top side of first layer is for radiation element, then the top side of bottom layer is for feeding line and the bottom side of bottom layer is for groundplane. The truncation is set in the edge of radiation element at 45° from z-axis and 45° from x-axis. The investigation is performed by varying the shape of truncation on radiation element. Three different shapes of truncation, i.e. triangle-shaped, square-shaped, and ellipse-shaped, are applied for investigating the antenna parameter focused on its axial ratio. From the result, it shows that the antenna with ellipse-shaped truncation has the widest axial ratio bandwidth among other shapes ranges from the frequency of 7.89GHz to 8.4GHz.