Photonics-assisted Microwave Signal Processing Based On Stimulated Brillouin Scattering

In the past three decades,microwave photonics has emerged as an innovative technology for microwave signal generation,distribution,control,and detection.As an interdisciplinary discipline,microwave photonics can leverage many advantages of photonics to solve problems that are difficult in the microwave field.Compared with traditional microwave signal processing solutions in electronics,microwave photonic signal processing solutions focus primarily on the optical domain processing of signals,and the introduction of photonics makes these processing scheme have the good parallel processing capability,extremely low transmission loss,and extra-large processing bandwidth.Photonics-assisted microwave signal processing has attracted extensive attention from scholars at home and abroad,especially in filtering,delay,phase shift,measurement and so on.At present,many photonics-assisted microwave signal processing schemes with large instantaneous bandwidth,wide frequency coverage,low loss and strong immunity to electromagnetic interference have been proposed.Photonics-assisted microwave signal processing is very promising,and among many photonics-assisted microwave signal processing schemes,those based on the stimulated Brillouin scattering(SBS)effect are particularly outstanding in flexibility and practicality.The characteristics of Brillouin gain spectrum and attenuation,such as flexible controllability and high selectivity,make SBS-based signal processing schemes perform well in the fields of signal filtering,measurement,phase shift.In addition,the SBS effect provides the possibility of real-time processing of signals oriented to the time-frequency dimension.In this paper,a time-frequency oriented real-time microwave signal processing scheme is studied based on the SBS effect,mainly focusing on two important applications,the acquisition of two-dimensional timefrequency parameters and the improvement of signal-to-noise ratio(SNR)in the signal band.In terms of the two-dimensional time-frequency parameter acquisition,two photonics-assisted signal processing schemes are proposed,namely,the parallel SBS time-frequency analysis link and the time-divided SBS time-frequency analysis link.and the time-frequency analysis capability of these links is verified by simulation and experiment.Experimental and simulation results show that the parallel SBS timefrequency analysis link is able to perform real-time and efficient time-frequency analysis of microwave signals with large bandwidth,while the time-division SBS timefrequency analysis link is able to perform high-resolution time-frequency analysis up to 15 MHz for periodic microwave signals.In terms of SNR enhancement in the signal band,a time-varying microwave photonic filter(TV-MPF)based on the SBS effect is proposed in this paper.TV-MPF is applied to suppress in-band noise of broadband arbitrary microwave waveforms in real time through experiments,which can effectively improve the waveform quality of microwave signals.The TV-MPF is expected to provide efficient and real-time noise cancellation solutions for radar,communication and other fields.This paper opens a new perspective for building a real-time and efficient photonics-assisted microwave signal processing system,that is,real-time processing of signals in the two-dimensional time-frequency dimension with the advantage of SBS effect.The introduction of time-frequency dimensional processing makes the system more flexible and practical and is expected to provide new technical support for future cognitive radar,electromagnetic spectrum warfare,radio astronomy and other fields.