Stochastic Analysis of Laser Phase Noise in Photonics-Assisted Radio Frequency Beamforming
This paper develops a stochastic model for quantifying the impact of laser phase noise on photonics-assisted radio frequency (RF) beamforming. Unlike conventional deterministic models, the presented theoretical framework captures the statistical randomness associated with the RF array factor of beamforming networks driven by finite-linewidth lasers. Fourier-domain analysis reveals that laser phase noise reshapes the spatial coherence function of such beamforming networks, inducing coherent RF aperture shrinkage, beam-pattern distortion, and directivity degradation. The analysis highlights that beamforming network architectures employing nanosecond-scale optical differential delays can exhibit substantial performance degradation even when driven by commercially available narrow-linewidth (kHz-range) lasers. Furthermore, it is demonstrated that average RF power gain gets downscaled and fluctuations dominate in large-aperture beamforming networks due to phase noise, imposing an upper limit on the maximum achievable RF antenna array-size. The reported results highlight the quantitative performance and scalability limits imposed by laser phase noise in photonics-assisted RF beamforming, offering key design guidelines for implementing large-scale beamforming networks in next-generation wireless communications, sensing, radar, and radio astronomy applications.