A shared-aperture dual circularly polarized antenna array for satellite communication

A dual circularly polarized antenna array with high gain, good axial ratio and low sidelobes for satellite communication is proposed. The shared-aperture antenna can realize right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) radiation simultaneously at S band by using a directional coupler connected with an H-shaped aperture coupling network and a coplanar microstrip feed network. The two feed networks, which share the same ground in the center, are arranged on the both sides of the ground respectively. This arrangement ensures a good linearly polarization purity and thus good RHCP and LHCP characteristics. In order to reduce the sidelobes of the antenna array, the whole array is divided into sixteen sub arrays of 2×2 elements. The amplitudes of the 16 sub-array are arranged appropriately in a taper distribution which can be realized by a relatively simple feeding network. The simulation results show that the as-designed 8×8 antenna array has a very good performance: a -10dB return loss bandwidth of 20%, a -3dB axial ratio bandwidth of 18%, a 35dB copolar-crosspolar ratio level and the peak gains better than 25dBi for both RHCP and LHCP radiation with sidelobes below -18dB.