Frequency Synthesizer Based On Optoelectronic Oscillator

With the increasing requirements on future airborne equipment of the world's military revolution,the requirements on the performance of frequency synthesizer facing to future avionics are getting higher and higher.At this stage,the commonly used dielectric resonator oscillator or crystal oscillator of standard frequency source has a limited Q value,which makes it difficult to obtain lower phase noise at higher frequencies,thus the overall performance of the frequency synthesizer is severely limited.Based on the above problems,this paper firstly introduces the ultra-low phase noise optoelectronic oscillator as a frequency reference source in China,and a new high-performance synthesizer with high-frequency large bandwidth,high stability,low phase noise and fast agile frequency has been studied and designed.The main research contents and innovations in this paper include the following three aspects:1.The frequency synthesis technology is analysed and experimentally studied,the factors affecting the phase noise of PLL are discussed.According to comparison of experiments,pros and cons of the synthesized signal quality based on the standard frequency reference source and ultra-low phase noise reference source are vertified.Using a reference source with lower phase noise can improve the signal synthesizer's signal quality is pointed out.2.The practical prototype of the optoelectronic oscillator based on the injection-locked dual-loop architecture is developed,and the phase noise,the frequency stability and the spurious suppression ratio are well balanced.The output signal is 10GHz,phase noise is-136dBc/Hz@10kHz,the side mode rejection ratio is>80dB,and the Allan variance is 6.52x10^-12 at 1s.It is an ideal frequency reference source,the phase noise has a 16dB improvement compared with the high performance dielectric resonator oscillators（approximately-120dBc/Hz@10kHz）at present in the electronics field.3.Based on optoelectronic oscillator,combined with the mixer PLL and direct analog frequency synthesis technology,a high-performance frequency synthesizer is produced.The frequency step is2MHz,frequency conversion speed<1.5μs,spurious<-65dB,phase noise is-125dBc/Hz@10kHz to-135dBc/Hz@10kHz in the range of 5.9GHz-12.9GHz.Comparing with similar products domestic and overseas,the phase noise improves by 15dB and 8 dB respectively at 10kHz offset,which fully meets the requirements of future avionics systems.