Analysis of phase noise in a spin torque oscillator stabilized by phase locked loop

Abstract

This study analyses phase noise in a spin torque oscillator (STO) stabilized by phase locked loop (PLL). Time domain measurement showed that phase error of the 6.996 GHz signal generated by a STO, which exhibited a random-walk type fluctuation under free running, was suppressed within a standard deviation of 0.408 rad by the PLL. Power spectrum under phase locked oscillation indicated that the PLL had a loop bandwidth of approximately 16 MHz, thus effectively suppressing phase error below 10 MHz. However, it was also found that power spectrum of the residual phase error was distributed much higher than the loop bandwidth.