Study On Phase Noise Modeling Of Fractional-N Frequency Synthesizers

Output phase noise of the fractional-N frequency synthesizer can reach-116 d Bc/Hz@600k Hz,-133 d Bc/Hz@3MHz in the DCS-1800 system. While for the DCS-1800 system in a recent report, a new designed fractional-N frequency synthesizer output phase noise is less than-124 d Bc/Hz@600k Hz and-142 d Bc/Hz@3MHz. However, this literature would not have in-depth study of the reasons that the new fractional-N frequency synthesizer output phase noise has been dramatically improved. Therefore, the analysis and research of the cause that the new fractional-N frequency synthesizer could reduce output phase noise has important practical significance.In this paper, studied phase noise of a novel fractional-N frequency synthesizer in a clear system structure and on the basis of its key function module working on, focus on the phase noise mechanism and modeling of charge pump and phase frequency detector on the actual working conditions. The studied phase noise mechanism of charge pump in this paper i nclude: input signal of different modes under the control phase noise of charge pump, the phase noise due to nonlinearity of charge pump(current gain mismatch and current dynamic mismatch). The studied phase noise mechanism of phase frequency detector include: phase noise caused by the timing jitter in phase frequency detector and phase noise due to reset delay mismatch.To verify the validity of phase noise modeling of the established charge pump and Phase frequency detector, this paper, on the basis of MATLAB simulation calculations and experimental data analysis and in combination with other functional modules classical and complete phase noise model, conducted ADS behavioral simulation for the new fractional-N frequency synthesizer system, and compared with the literature data, It can be concluded that the model is available.