Experimental characterization and modeling of low-cost oscillators for improved carrier phase synchronization

Phase noise performance is measured for nine different crystal oscillators, each suitable for use as a frequency reference in applications such as software defined radio and coherent cooperative communication systems. The phase noise measurements are parametrically fit to a standard two-state oscillator model to characterize the short-term and long-term stability parameters of each oscillator. A three-state model is also developed to provide a better fit to the measured phase noise spectrum for some of the tested references. In addition to providing a better fit to the measured phase noise spectra, the three-state model enables improved phase estimation and prediction performance. A numerical example is presented in which a Kalman filter derived from the three-state model shows up to 3dB improvement in mean squared error compared with the two-state model.