For running simulations in IE3D Zeland Software, finite ground plane is considered for Antenna 1 and infinite ground for Antenna 2.
Antenna 1: Several designs with the feed point position along Y-axis and slit length (LS) on ground plane for left- hand CP operation were studied. Figs. 3 (a-b) shows return loss, axial ratio (AR) against frequency for case 1 of Ls = 15 mm, WS= 1mm, XS = YS = + 6.5 mm. The axial ratio bandwidth of 0.43% at centre frequency, total gain of 2.51 dBi and total directivity of 5.42 dBi are obtained at 1.966 GHz.