Research On Low Spurious Microwave Signal Generation Based On Injection-Locked Optoelectronic Oscillator

Ultra-low phase noise and high spectral purity microwave or millimeter wave signals can be used in high-performance communication systems,radar,and electronic measurement systems.Optoelectronic Oscillator(OEO)has ultra-low phase noise due to the use of long optical fibers in the feedback loop,and it is a highly competitive method for generating high-frequency microwave signals with low phase noise.However,an optoelectronic oscillator with a long fiber feedback loop will produce multiple densely distributed longitudinal modes,making single-mode oscillation difficult to achieve.Therefore,injection-locked OEO has been widely studied as a structure that can achieve single-mode oscillation,and this paper aims to study the oscillation characteristics of injection-locked OEO under single tone injection or multi-tone injection,and improve the spurious suppression ratio of injection-locked OEO output signal.This paper focuses on the following:1.The spectrum and phase noise of the signal generated by the single-loop OEO under different single mode fiber lengths are experimentally measured,and the spectral and phase noise characteristics of the OEO are theoretically deduced.The operation principle and phase noise model of the dual-loop optoelectronic oscillator are introduced,and the spectral characteristics and phase noise characteristics in the dual-loop structure are studied.2.The oscillation characteristics of an injection-locked OEO under single-tone injection are studied.The oscillation characteristics of injection-locked OEO are theoretically derived,the maximum injection-locked range is obtained by solving the phase differential equation of injection-locked OEO,and the phase noise model is established.Experimental results are performed on spectrum and phase noise of the signal generated by injection-locked OEO under different conditions.3.single-tone extraction from multi-tone microwave signal based on injectionlocked optoelectronic oscillator is investigated and experimentally demonstrated.Due to the OEO loop filtering and injection locking effect,the sidebands of the injection multitone signal can be obviously suppressed when its modulation frequency is not equal to the FSR of OEO.The experimental results presented that the carrier signal with a frequency of about 9.9972 GHz,sideband suppression ratio of 46.66 dB,and phase noise of-114.97 dBc/Hz@10 kHz was recovered by the OEO injected by a AM signal with a modulation frequency of 150 kHz and power of-10 dBm.