Hello, I am trying to simulate oscillator noise by following the procedure outlined in James Barnes' paper: "Simulation of Oscillator Noise" (1984) 28th Annual Frequency Control Symposium. In the paper, Barnes explains the models of the five typical types of noise that occur in oscillators and a method for their simulation.
I've followed the steps he presents in his paper and have been unable to produce simulated output for flicker FM noise that leads to an flat Allan variance graph (ie. all Allan variance values are nearly constant for all tau values). Instead, the Allan variance values of my simulated flicker FM noise start out constant at the Allan variance value I desire but then tend upwards by two to three orders of magnitude (nearly every simulation) about halfway through the range of possible tau values. In short, it starts out flat and then increases rapidly about halfway through the tau range. I believe there may be a couple possibilities and am wondering if anyone else has come across the same issues or knows of a solution. 1) To simulate flicker FM noise, Barnes uses a set of ARIMA coefficients to model the noise. Is an updated set of coefficients available that would have better accuracy or produce better simulation results? Is the ARIMA method typically used with the availability of today's higher computational power? 2) Barnes devotes a section of the paper to random number generation and states that the random numbers to be used should be normally distributed with zero mean and unit variance. I used the built-in Matlab command randn() to generate the random data but only achieved an all-flat Allan variance plot when the random number generator was seeded with a particular number. The majority of the time (using a "random" seed), this method produced non-flat results as described above. I then attempted the two methods Barnes presents in his paper to generate the random numbers which provided similar non-flat results. Are random normally distributed random numbers optimal for these simulations? Would another distribution produce results consistent with the expectation of an all-flat (ie. constant) Allan variance for flicker noise? I appreciate any advice or ideas you or your colleagues can provide. As needed I can provide individuals my generated Allan variance plots, but I didn't want to send them to the whole mailing list. Thank you in advance, Kyle _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
