Study On Coupled Opto Electronic Oscillators For 5G Communication System

With the rapid development of communication technology,the business volume of electronic systems has increased rapidly,and the technology demand for integration of high-frequency,broadband and multi-band frequency has raised great challenges to the electronic systems in the future.As the core module of the radio frequency receptor front,the oscillator directly determines the signal processing capacity of the communication system.Since there are some difficulties for traditional microwave oscillator to improve phase noise,frequency tuning range and other indicators,the optoelectronic oscillator(OEO)technology integrating microwave and photon technology is introduced to solve the key problems of the RF receiver front-end,which has become an important research direction.With the RF receiver front-end of5 G communication systems as the application context,this essay establishes phase noise phase domain model and frequency tuning model of coupled optoelectronic oscillator(COEO),and then studies profoundly the key technologies and system design of broadband frequency tunable COEO.Based on the quantitative model of the influences of local oscillator on microwave photon down-conversion system,a microwave photon down-conversion system with dual local oscillators structure is designed to verify the performance of the tunable COEO.Specific arrangement of the thesis is as follows:1.To make the broadband of COEO tunable,a kind of voltage-controlled adjustable fiber Fabry-Perot coupled optoelectronic oscillator(FFP-COEO)is put forward for the first time The oscillator does not require the laser light source for energy,and can control the cavity length of the Fabry-Perot cavity by voltage,which in turn can change the starting frequency and make the COEO frequency adjustable.The working bandwidth is 24-38 GHz.When the output frequency of the oscillator is 24 GHz,the side-mode suppression ratio can reach 47.4d B and the output power is larger than11 d Bm,so that it can provide high performance local oscillator signals for 5G New Ratio(5G NR)FR2 wave band(24.2-52.6GHz)based on orthogonal frequency division multiplexing technology(OFDM).2.Based on the application requirements of 5G NR communication FR1 frequency band(450MHz-6GHz),a low phase noise frequency-tunable COEO is designed based on the fiber grating Sagnac loop.The starting frequency is changed by adjusting the Sagnac loop arm length difference and spectral wavelength interval.The working bandwidth of the oscillator is 1.3-18.3GHz,and the frequency tuning step size is 20.2MHz/0.01 mm.The phase noise of the system is further optimized by improving optical loop filtering performance and adding a second mode-locked loop.When 18.3GHz microwave signal is generated,the phase noise is only-126 d Bc/Hz@10KHz.3.The influences of local oscillator on microwave photon down-conversion system are analyzed profoundly and the quantitative model of the influences of DC bias voltage and phase noise of local oscillator on microwave photon down-conversion system is established,which is verified through Optisystem software simulation and data analysis.The quantitative model can provide references for the design of microwave photon down-conversion system.4.According to the 5G NR communication FR1 frequency band(450MHz-6GHz)and the quantization model,the dual local oscillator structured microwave photon down-conversion system based on tunable COEO and microwave voltage controlled oscillator(VCO)is designed,and the performance of each channel of this system is verified by experiments.The system adopts multiplexed local oscillator source architecture and divides the radio frequency received by phase-frequency detector(PFD)and voltage comparator into high and low frequency bands.The local oscillator is selected by the comparator outputting high-low level control optical switch.Dual local oscillator structured microwave photon down-conversion system can not only solve the problem that the OEO is hard to provide low frequency local oscillator signal but also can increase or decrease the passage number of local oscillator as required by different communication frequency bands,which helps the system to expand new frequency band.The microwave photon down-conversion system of this structure has rigorous reconfigurability.This thesis studies the COEO that can be used in 5G communication,adopts optical loop route to replace laser source structure,and change the output spectral mode interval by tuning the parameters of comb filter cavity,so as to achieve the objective of broadband tuning.Compared with the existing OEO,the proposed oscillator has the significant advantages of low phase noise and large tunable bandwidth.In addition,combined with the quantitative model of the influence of the local oscillator source on the microwave photon down-conversion system,the performance advantages of broadband frequency tunable COEO are verified by designing the dual local oscillator structured microwave photon down-conversion system.The results of this study will be helpful to promote development and application of 5G communication system.