Dimensioning of a multibeam coherent photonic beamformer fed by a phased array antenna

Abstract

The design and dimensioning of a photonic-aided payload for a multi-beam high-throughput communications satellite is a complex problem in which the antenna, RF and photonic subsystems must be considered as a whole for achieving best performance with lowest mass and power consumption. In this paper, we propose and dimension the receiving stage of a communications satellite comprising a phased array antenna (PAA) feeding a multibeam photonic beamforming system (PBS). The PBS uses a single wavelength and resorts to heterodyne detection such that the retrieved beams are frequency downconverted. End-to-end system modeling shows that the complexity of the PAA and PBS can be traded-off for signal-to-noise ratio (SNR) or power consumption without compromising the beam width. The dimensioning of a realistic scenario is presented, showing that an SNR and beam crosstalk on the order of 20 dB are achievable with a total power consumption below 1 kW for a typical number of 100 antenna elements (AEs).

Modular coherent photonic-aided payload receiver for communications satellites

“…Frequency down-conversion is accomplished by heterodyning the beam with a local oscillator (LO), which is typically derived from a single reference oscillator 3 . A photonic-assisted payload receiver should likewise resort to heterodyne detection, with optical local oscillators (OLOs) taken from a single reference OLO, thus resulting in self-heterodyne detection 5,20 . Self-heterodyne detection has the important advantage of cancelling laser phase noise, which relaxes the required laser linewidth, and makes the proposed MCL possible.…”

“…In practice, such a matrix is implemented by a processor denominated by beamforming network (BFN), and each coefficient is implemented by an amplifier or attenuator combined with a phase shifter. In terms of scale, the required number of feeds increases only inversely to the minimum beam width, resulting in the lowest possible number of feeds 3,5 . As for flexibility, a full-scale reconfigurable BFN is able to adapt to any set of beams.

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“…A photonic-aided payload implements the BFN with a programmable photonic processor, resulting in an optical beamforming network (OBFN) 5,7,8 . A miniaturizable OBFN must be identical to an RF BFN, with an optical phase shifter being equivalent to an RF phase shifter.…”

“…A miniaturizable OBFN must be identical to an RF BFN, with an optical phase shifter being equivalent to an RF phase shifter. Consequently, a miniaturizable OBFN relies on coherent optical signal processing, which in turn enables coherent detection 3,5,9,10 . Coherent detection can also provide heterodyning, thus enabling RF frequency conversion 3,5,11 .…”

“…Consequently, a miniaturizable OBFN relies on coherent optical signal processing, which in turn enables coherent detection 3,5,9,10 . Coherent detection can also provide heterodyning, thus enabling RF frequency conversion 3,5,11 . As a result, RF hardware is assigned only to basic tasks such as amplification and inverse/output multiplexing 3 .…”