Optoelectronic beam-forming network for a spaceborne phased-array antenna

Abstract

Optoelectronic techniques offer major benefits in the construction of space-borne phased arrays with stringent performance requirements, not only in signal distribution functions but also in the beam forming processing itself. In the course of a current project for European Space Agency we have designed the constructed proof of concept hardware to demonstrate the use of coherent optical techniques in the formation of antenna beams. The scenario at the basis of our study is for a telecommunication satellite with a 160-element phased array antenna, forming 15 beams, each of which can carry up to 20 QPSK modulated carriers, with up to 6 operating simultaneously. Operation is in the 12/14 GHz bands for downlink and uplink operation respectively. In our beamforming concept we have employed an optical heterodyne approach in which the phase shift and amplitude required for beamforming is imposed upon an optical carrier, the RF waveform required for transmission being derived subsequently by mixing with an optical local oscillator signal. Phase encoding for data modulation is also carried out in the optical domain.