Abstract
We present a novel, power and hardware efficient, antenna system
leveraging the eigenmodes of the over-the-air propagation matrix from an
active multi-antenna feeder (AMAF) to a large reflective intelligent
surface (RIS), both configured as standard linear arrays and placed in
the near field of each other. We demonstrate the flexibility of the
proposed architecture by showing that it is capable of generating
radiation patterns for multiple applications such as very narrow beams
with low side lobes for space-division multiple access communications,
wide-angle beams for short range automotive sensing and sectorial
beaconing, and monopulse-like patterns for radar angular tracking. A key
parameter in our design is the AMAF-RIS distance which must be optimized
and it is generally much less than the Rayleigh distance. For a given
AMAF aperture, the optimal AMAF-RIS distance increases as a function of
the RIS size. The AMAF-RIS loss is compensated almost exactly by the
larger aperture gain of the RIS leading to almost constant RIS gain with
increasing RIS sizes. This allows to choose different beam angular
selectivities with the same center beam gain. Active RF amplification is
done at the AMAF only, thus resulting in a much higher power efficiency
and much lower hardware complexity than conventional phased arrays with
same beamforming performance.
Accepted for the IEEE ICC 2023, Rome