Reconfigurable Low Phase Noise RF Carrier Generation up to W-band in Silicon Photonics Technology

Reconfigurable radiofrequency (RF) signal generation in the 30–300 GHz range is attractive for many applications. W-band (75–110 GHz) is currently targeted by both wireless and satellite communications and similar frequency ranges are employed for on-board automotive radar systems. Distribution of high-precision and high-frequency synchronization signals in modern centralized radio access networks might be addressed by radio-over-fiber solutions, but the stringent phase noise (PN) requirements in case of broadband signals with high subcarriers density are not easily attainable through conventional electric-domain solutions. This article reports on the performance of a monolithically integrated silicon photonics (SiP) circuit employed for RF carrier synthesis. Up to sixfold frequency multiplication of an 18.5 GHz reference clock is demonstrated with low additional phase noise. The circuit includes a high-speed electro-optic phase modulator employed for optical frequency comb (OFC) generation and a tunable distributed feedback resonator (DFBR) filter for selecting the desired OFC harmonic. The beating of the OFC tone with the input laser mode in an off-chip photodiode generates the target RF carrier wave. By tuning the reference clock and the DFBR filter, reconfigurable frequency generation up to W-band and beyond is achieved. PN and time jitter (TJ) of the generated RF carriers are experimentally measured, demonstrating a similar performance as of an ideal frequency multiplier. The effect of the noise of DC sources employed for filter tuning is assessed and a counteracting solution is implemented. TJ robustness versus laser drifting is analyzed and the potential for up to elevenfold frequency multiplication (203.5 GHz) is shown.