Ultra-wideband mm-wave remote antenna unit for radio-over-fiber distributed antenna systems in silicon photonics.

This article presents what we believe to be a novel chip-scale 25-45-GHz re-configurable mm-wave remote antenna unit (RAU) for radio over fiber (RoF) distributed antenna systems. The proposed RAU architecture optimizes energy efficiency by operating directly at mm-wave frequencies, and spectral efficiency by selecting re-configurable RF photonic filters topology. Additionally, it achieves frequency agility by rejecting interferes and a small form factor by utilizing the SOI photonics process. Two photonic integrated circuits (PICs) that act as downlink and uplink units are presented while occupying a total area of 12.33 mm². The downlink selects a single channel within the desired frequency range, while the uplink rejects up to four interferes. The building blocks of the proposed architecture are discussed and their design consideration and parameters are shown. Then, a comprehensive system analysis of the proposed RAU architecture including key performance indicators is presented. A scalable 5-channel system is demonstrated each with a 3-dB Bandwidth of 5-GHz. Moreover, this architecture can be continuously tuned and re-configured within a wide frequency range to cover all 5-channels. To the best of the authors' knowledge, this is the first wideband modular and re-configurable mm-wave RAU that covers the entire mm-wave sub-45-GHz band implemented in silicon photonics.