Figure 3

(a) System layout of dual-servo control for stable fr-sweeping. (b) Experimental results of fr-sweeping. The command fR signal (blue) for fr-sweeping as initiated by the trigger signal (red) and the error signal of fR − fr (green) used as the control input. (c) Allan deviations of the fR − fr error signal (green) and the fr signal (blue) measured from the frequency counter during fr-sweeping control.