Research On Mathematical Model And Measurement Method Of Pulse-modulated Signal Phase Noise

Phase noise is an important indicator to describe the short-term stability of the frequency source in the frequency domain.With the rapid development of radar technology,the demand on the stability of frequency sources is higher and higher,phase noise is an important indicator to determine the performance of the radar.Therefore,it is very important to accurately measure the phase noise of the signal.Through the research of this paper,it is found that the phase demodulation method and power-law model cannot accurately measure the phase noise at the near carrier.Therefore,a compensable method and an improvement model is proposed for these two measurement methods respectively in the paper,which solves the inaccurate question.at the near carrier.The transmitted signal by the radar is a pulse-modulated signal,where the phase noise is very difficult to measure.The paper proposed a mathematical model for measuring the phase noise of the pulse-modulated signal,which is effectively to measure the phase noise of the pulse-modulated signal.The main contents of the paper are:(1)For the phase demodulation method,the phase noise measured at the low-frequency offset of the phase noise is attenuated(It is also called the low-frequency defect question).By analyzing the circuit composition and the measurement of the phase demodulation method,the mechanism of the low-frequency defect problem is studied.The paper Proposed a suitable compensable method,the experiment result shows that the method proposed in the paper can effectively compensate the low-frequency defect question,and improve the near-carrier measurement performance of the phase demodulation method,expand the measurement bandwidth of the phase demodulation method.(2)An experimental research based on the power-law mathematical model to measure the phase noise found that the power-law mathematical model cannot fit the phase noise of the near carrier(within about 1 Hz from the center frequency).In the paper,a new mathematical model is established to measure the near-carrier phase noise.It is combined with the power-law mathematical model to measure the phase noise in segments,which improves the performance of measurement in the near carrier segment and the measurement bandwidth of the mathematical model,the paper provides a new solution for the problem of measurement difficulty at the near carrier.(3)A series of problems are analyzed after generating the pulse modulation signal through simulation experiment,such as sideband aliasing and periodic noise,the phase noise mathematical model of the pulse modulation signal is established in the paper.The mathematical model is used to measure the phase noise of the pulse modulation signal,and it is further measured the phase noise of carrier signal using the least squares fitting method.Finally,the experiment verifies the validity of the phase noise measurement of the pulse modulation signal.The paper provides a feasible solution for low-cost measurement of the phase noise,and a solution to the difficulty of measuring the phase noise of the frequency source signal under the condition with radar working.