An S-Band-Receiving Phased-Array Antenna with a Phase-Deviation-Minimized Calibration Method for LEO Satellite Ground Station Applications

Abstract

This study presents a new S-band-receiving phased-array antenna with a phase-deviation-minimized calibration method for the ground station of a low Earth orbit (LEO) satellite. The proposed antenna consists of 16 subarrays, 16 beamforming receiving RF modules (BF-RFMs), a power/control board, and a 16-way feed network. The subarray was achieved by joining two 8 × 1 arrays with a two-way power combiner. The 16-element antenna subarrays showed a gain of 16.1 dBi and a reflection coefficient of less than −10 dB from 2.12 GHz to 2.45 GHz. The BF-RFM, which consists of three low-noise amplifiers (LNAs), a power combiner, a phase shifter, and a digital attenuator, was designed and fabricated. The BF-RFMs were provided by the power/control board and showed a gain of 30.8 ± 0.8 dB, an amplitude root-mean-square (RMS) error from 0.25 dB to 0.28 dB, and a phase RMS error from 1.8° to 2.5° over the Rx frequency range. The arrangement procedures of the 16 BF-RFMs are presented to increase beam pointing accuracy at the desired angle. A commercial 16-way feed network was employed to combine all the output ports of the 16 BF-RFMs. The assembled antenna, which has dimensions of 1.58 m × 1.58 m × 0.2 m, was measured by partial and full scans in the near-field scanning system. The back-projected algorithm was employed to calibrate the antenna’s gain patterns in the partial scan. The implemented phased-array antenna had a gain greater than 28.14 dBi, sidelobe levels less than −17.1 dB, and beam pointing errors less than 0.07° over the beam pointing angle of −20~+20°. Based on the implemented antenna system, we conducted a field test using KOMPSAT-5, which is actually operating in South Korea, in order to verify the performance of the low Earth orbit (LEO) satellite ground station system.