Research On Broadband Radio-Frequency Signal Generation Based On Photon Technology

Moderm society has entered the era of informationization.and the widespread application of radio frequency(RF)signals is one of the important features of the information age.RF signals have important applications in basic research,wireless communications,bio-imaging,and radar systems.Increasing communication rates,high-quality bioimaging,and high-resolution radar systems have created significant demands on the quality and bandwidth of RF signals.Traditional RF signals generated by electronic technology have failed to meet the above requirements.Photonics-assisted RF signal generation technology has received much attention due to its obvious advantages in signal quality,bandwidth,integration,and low power consumption.This paper studies the broadband RF signal generation technology based on photonic technology.Photonic microwave technology based on femtosecond lasers can obtain microwave signals with the best spectral purity,but still not enough for broadband and fast tuning.Modern electronic systems typically require low-phase-noise,wideband adjustable,fast switching,multi-band microwave signal sources.The existing technical solutions still appear insufficient in broadband tuning and fast frequency switching.This paper proposed a technique based on frequency transform pair to achieve low phase noise extraction of any harmonics in photogenerated microwaves.Compared with the prior art,the scheme based on the frequency conversion pair has the following advantages:(1)effective AM-PM coupled noise suppression;(2)wideband tuning range,fast tuning speed;(3)high photoelectric conversion efficiency.This paper first proposes a new type of opto-electronic oscillator(OEO),namely chirp-oscillation OEO.This new type OEO breaks through the limitations of traditional OEO in generating frequency agile signals,which can support a large number of modes while stabilizing oscillations.A frequency-scanning filter is introduced into the opto-electronic cavity to replace the static filter in the conventional OEO.The frequency-scanning filter forces the amplitude and phase between these oscillating longitudinal modes to have specific values to obtain the desired signal.In particular,chirp-oscillation OEO is capable of generating large bandwidth,large delay,low noise frequency modulation(FM)signals,from which the radar systems are expected to obtain better performance.Conventional researcs on OEO are focused on continuous single-frequency microwave signal generation.The chirp-oscillation OEO proposal expands OEO's research direction and provides prototypes for OEO to generate more complex waveforms and achieve more functionality.In conventional delay-line-based oscillators,the natural frequency is limited to the cavity delay and its output frequency can only be a specific discrete frequency due to the linear/quasilinear evolution of the signal phase.This paper first proposed another new type of OEO,the opto-electronic parametric oscillator(OEPO).By introducing a nonlinear parametric process into the conventional OEO.the signal suffers a nonlinear phase jump as it propagates through the cavity,ultimately making the longitudinal mode of the oscillation no longer limited to the cavity delay.OEPO can achieve stable,multi-longitudinal-mode oscillation and output broadband microwave signals.By tuning the external local oscillator,the OEPO can achieve stable oscillation at any frequency,which breaks the discretization of the oscillation frequency in a delay-line-based oscillator.