A Design Of A Ultra-Low-Phase-Noise Oscillator And A Study On Measement Of The Phase Noise Of Amplifier

Phase noise refers to the ratio of signal noise density within unit bandwidth and total signal power.It is shown as random drift of carrier phase.Phase noise is an important index of evaluation of oscillator frequency spectrum purity.As the development of military,radar and deep space exploration,the design of ultra-low-phase-noise frequency sources has become an important task for engineers.Sapphire Loaded Cavity(SLC)has become an excellent choice for designing ultra-low-phase-noise oscillators because of its high quality factor.Combined with low phase noise amplifier and frequency lock loop(FLL),SLC can effectively improve the frequency stabilization and phase noise performance of the oscillator,In this paper,we designed a low phase noise sapphire oscillator and studied the methods of phase noise measurement.First of all,in order to have a more in-depth understanding of oscillator's phase noise,this article first introduces the basic theory of oscillation of feedback oscillator.Based on the oscillation and the feedback theory,Leeson's model of phase noise was derived.And with the help of Matlab,the parameter optimization of the model are analyzed.The third chapter of this article describes the realization of the sapphire basic oscillation loop.The influence of the phase noise of amplifier to oscillator phase noise performance is analyzed.Low phase noise loop amplifier was designed.Then,the main oscillation loop was build.And by the use of phase noise analyzer,the phase noise performance was measured.The results shows the phase noise performance has reached-108 dBc/Hz @ 1 KHZ and-132 dBc/Hz @ 10 KHZ.Then,the fourth chapter of this article mainly introduced the realization of the frequency lock loop(FLL).The effect of improving phase noise of better frequency stability is analyzed.The frequency lock loop(FLL)based on the phase detector using double balanced mixer was then analyzed and achieved.We built the sapphire oscillator frequency lock loop(PLL)based on phase discriminator,and realized the dynamic stability of the oscillator frequency.We tested and analyzed the different phase noise performances of the loop with different low-frequency gains and filtering bandwidths.Finally,two-port device(RF-amplifier)additional phase noise measurement system based on the interferometric structure was designed.Experiments showed that the bottom phase noise of this measurement system reached-170 dBrad2/Hz,which is far less than the bottom of classical phase noise measurement system.Then,the article also carried on the exploration of the implementation of frequency source phase noise measurement system.