Figure 8.

(a) Phase error of the SPD and TPD phasemeters with step frequency difference. (b) Frequency responses of the SPD and TPD phasemeters with step frequency difference. With a frequency step of 50 kHz, both the SPD and TPD phasemeters track the phase well. With a frequency step of 60 kHz, the SPD phasemeter induces a phase error of 1 cycle, called the cycle slip. The corresponding frequency response of the SPD phasemeter also shows a cycle of ups and downs when the step frequency is beyond the fast-acquiring range.