PCM Assisted Compact Optical Beamformer: A Step Towards Next-Gen Wireless Communication

The future of wireless communication (5/6G) relies on energy-efficient, low-latency, broadband, ubiquitous space-to-ground connection through phased arrayed antennas (PAAs) integrated into satellite constellation in LEO. The traditional electronic beam forming network (BFN) feeding the PAAs suffers from beam-squinting effect, limiting operating bandwidth (BW). The SOI photonics-based microwave optical BFN can remove this bottleneck, resulting in different BFNs based on gratings, ring resonators, interferometers, etc [1]–[2]. Amid them parallel arrays of optical switched delay line-based beamformers catch particular attention due to their simple design, stability, and ability to extend the operating bandwidth (>10 GHz). However, the beam pointing angle scales inversely to the antenna number, resulting in poor steering resolution. Recently this constraint has been removed by scaling the basic delay unit <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\Delta\tau)$</tex> between the adjacent line linearly in a 5-bit structure, with a maximum RF frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{f}_{\max})$</tex> of 18 GHz [3]. However, the technique generates a beam-squinting effect in the negative beam-pointing angles which was more recently overcome through a pre-compensation unit [4], where a 5-bit beamformer with maximum possible beam pointing angle of 2<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup>, independent of antenna numbers and squint-free beam shape over 20 GHz of BW and f<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> = 30 GHz were demonstrated. However, the reported structures use metallic heaters as the tunning agent, requiring a continuous power supply and a larger footprint due to thermal cross-talk.