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 (Δτ) between the adjacent line linearly in a 5-bit structure, with a maximum RF frequency (fmax) 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 25, independent of antenna numbers and squint-free beam shape over 20 GHz of BW and fmax = 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.