CMA-Based Four-Element Broadband Circularly Polarized Octagonal-Ring Slot Antenna Array for S-Band Satellite Applications

This research proposes a low-complexity and low-profile four-element circularly polarized (CP) octagonal-ring slot antenna array with sequentially-rotated feed network for S-band satellite applications. The proposed antenna array is characterized by characteristic mode analysis (CMA). One single element of the CP octagonal-ring slot antenna array consists of a C-shaped monopole on the upper layer functioning as the radiating patch; and an octagonal-ring slot patch on the lower layer functioning as the ground plane. The four elements are connected by a sequentially-rotated feed network to enhance the impedance bandwidth (IBW), axial ratio bandwidth (ARBW), and gain. Simulations are performed, and an antenna prototype is fabricated and experiments carried out. The measured IBW and ARBW at the center frequency of 2.4 GHz are 91.6% (1.8 – 4 GHz) and 84.5% (1.97 – 4 GHz), with the maximum gain of 7.8 dBic at 3.3 GHz, rendering the proposed four-element CP octagonal-ring slot antenna array with sequentially-rotated feed network operationally suitable for S-band satellite communication. The novelty of this research lies in the use of CMA to characterize the circular polarization of the octagonal-ring slot antenna array; and the sequentially-rotated feed network to enhance the IBW, ARBW, and antenna gain of the four-element CP octagonal-ring slot antenna array with sequentially-rotated feed network.