Fourier Mode-locked Tunable Optoelectronic Oscillator Based On Ring Microwave Filter

As a new type of oscillator,photoelectric oscillator has attracted wide attention due to its high quality and low phase noise.Linear chirp signal or microwave frequency sweep source with low phase noise is an important component of radar and wireless communication system.Tunable photoelectric oscillator is a good scheme.In this paper,a fast tunable microwave filter with ring resonator is proposed and validated.On this basis,the principle of mode locking in Fourier domain is applied.A Fourier domain mode-locked tunable optoelectronic oscillator based on a ring resonator tunable microwave filter is proposed.Theoretical and experimental studies are carried out around the above-mentioned electrically tunable filters and tunable optoelectronic oscillators.The main innovations and research contents are as follows.The basic working principle of OEO is analyzed and derived theoretically.Based on the principle of ring resonance filter,the basic principle of ring resonance tunable microwave filter is studied.The optimization theory of the structure parameters of the filter is established by numerical simulation.Combined with the basic principle of the Fourier domain mode-locked laser,the working principle of the Fourier domain mode-locked tunable optoelectronic oscillator is theoretically analyzed,and the structural optimization analysis is carried out.In the aspect of ring resonator tunable microwave filter,the link of the proposed tunable microwave filter based on ring resonator structure is established and experimentally verified.1.Analyze the structure and select the components used in combination with matlab simulation and market research: low noise amplifier,tunable attenuator,voltage controlled phase shifter,qualitative coupler and isolator;2.Set up tunable filter links,and debug and optimize the links from loop gain and loop flatness.3.Test and analyze the main parameters of tunable loop filter: 3 dB bandwidth,stopband rejection,saturation output power,linearity,tuning speed and modulation bandwidth.The experimental results were as follows: the tuning bandwidth was 400 MHz(central frequency was 9 GHz),the tuning speed was 40.1 MHz /us,the 3 dB bandwidth was about 6 MHz,and the stopband inhibition was 40 dB.Based on the aspect of the tunable microwave filter Fourier mode-locked photoelectric oscillator,firstly,a typical single-frequency output OEO is constructed and its performance is tested.On this basis,the new structure of the Fourier domain mode-locked tunable optoelectronic oscillator based on the ring resonant tunable microwave filter is built,and the link is debugged and optimized from the aspects of loop gain and the time of Fourier mode-locked.Tunable photoelectric oscillator is studied from tuning range,linearity of sweep signal and phase noise.1.If the input voltage of the phase shifter is changed,the tuning range can vary from 0 MHz to 400 MHz.If the bias voltage is changed,the central frequency of the tuning range will change accordingly.2.Linearity was tested with oscilloscope combined with 89600 VSA software.The test results are as follows: when the frequency range is 400 MHz,the linearity is about 2.5%;when the frequency range is 140 MHz,the linearity is about 0.3%.In the use process,the appropriate frequency range can be selected according to the actual application and requirements.3.The phase noise performance is tested with a phase noise meter.The test results showed that the phase noise was tested every 100 MHz within the sweep frequency range of 400 MHz,and the phase noise was lower than-126 dBc /Hz at the frequency offset of 10 KHz.