Dual-Band Circularly-Polarized Antenna Forming Unit Configurations Featuring Polarization Selectivity and Diversity for Millimeter-Wave Satellite Applications

This paper introduces a dual-band dual circularly-polarized (DB-DCP) antenna configuration suitable for the simultaneous uplink and downlink (UL/DL) operation in satellite communication systems. The dual-band CP performance is realized by using a dual-band branch-line coupler (DB-BLC) with +/−90° phase offsets between the split ports at the dual frequencies. Either the dual-band same CP (DB-SCP) or the dual-band opposite CP (DB-OCP) antennas can be implemented through the proper selection of the DB-BLC topology. The opposite polarization feature at the two bands of the DB-OCP antennas further enhances the isolation between the UL and DL bands through additional polarization diversity. The selection of operating modes is achievable by switching the excitation ports, providing great flexibility for system applications. The proposed configuration features the ease of fabrication using standard 2-layer printed circuit board (PCB) technology, and its planar structure makes it easy for integration with other circuitries at the system level. The proposed designs have been experimentally validated. The measurement results of the DB-SCP and DB-OCP antennas revealed an applicable system bandwidth (the intersection of impedance bandwidth and the axial ratio bandwidth) of 9.42%/6.40% and 8.06%/4.50% at 28 and 38 GHz, respectively, with reasonable antenna gain and total efficiency.