A Silicon Photonics Automatically-Tunable mm-wave Remote Antenna Unit

This article presents a 25–40 GHz novel silicon photonics wideband re-configurable mm-wave remote antenna unit (RAU) for radio over fiber (ROF) distributed antenna systems. The proposed chip-scale RAU architecture achieves energy efficiency by directly operating at mm-wave frequencies, and a small form factor by utilizing SOI photonics process. A 4-channel system is demonstrated each with a 3-dB BW of 5-GHz. The RAU downlink photonic integrated circuit (PIC) consists of a tunable channel-select filter, and a mm-wave high-speed photodetector (PD), while the uplink PIC comprises of cascaded image-and jammer-reject filters, respectively. Moreover, the calibration algorithm for photonics process variation and further tuning of the RAU operating bands is discussed here. To the best of the authors’ knowledge, this is the first wideband tunable mm-wave RAU that covers the mm-wave sub-40-GHz.