Active Reflection Coefficients Distribution Study of Satellite Multi-Beam Antenna Array

This paper presents the active reflection coefficients (ARC) distribution measurement and analysis of an antenna array for direct-to-cell satellite communication systems. A 4×2 antenna array is built using patch antennas operating at 2.18GHz. A 30 dB coupler is also appended to each antenna element to sample input signals. An eight-channel signal transmitting and receiving platform using four universal software radio peripherals (USRP) are configured to process the baseband signals. The received signals of the USRPs are used to calculate the ARC of the antenna array. The transmitted signals follow the standard format of long-term evolution (LTE) orthogonal frequency-division multiplexing (OFDM). The modulation order, the number of beams, the maximum beam angle and the carrier frequency are investigated to explore factors that affect the ARC distribution. The measurement results show high agreement with theoretical simulations, demonstrating that the ARC distribution is mostly affected by the beamforming strategy, i.e., the number of beams and the maximum beam angle. The carrier frequency also affects the ARC through the change of the S-parameter matrix. These conclusions are crucial to the power amplifier design for active integrated multi-beam antenna arrays in direct-to-cell satellite communication systems.