Jackson Labs PHASE STATION 53100A, Руководство пользователя

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PhaseStation 53100A User’s Manual V1.04 25-Apr-2022 55
Working with phase- and frequency-difference traces
Phase and frequency stability data acquired by TimeLab is represented internally as an array of phase-
difference samples. This is true regardless of whether the data came from a frequency counter, a time-
interval counter, or a direct-digital timing analyzer. (Frequency readings are converted to phase-
difference samples on the basis of their deviation from the first frequency reading acquired.)
In addition to the statistical measurements such as Allan deviation that TimeLab provides, “strip chart”
views are available to give you a closer look at the raw phase-difference data. These views correspond
to the
Phase difference (Unwrapped) ( p ) , Phase difference (Original) ( w ) , and Frequency-difference ( f )
options on the
Measurement
menu.
Phase difference (Original) (w)
Phase difference (Unwrapped) (p)
The distinction between these two measurement types is relevant when receiving time-
interval data from a traditional counter. The
Phase difference (Original) ( w )
measurement shows the original TI samples as they arrive from the hardware.
When acquired from a TI counter, these readings are subject to “wraparound” when
they exceed the period of the signal that determines the START-to-STOP channel
interval. For instance, if an oscillator near 10 MHz is measured against a drift-free
source at exactly 10 MHz, the TI readings from the counter will increase or decrease
from one trigger interval to the next. When the START-to-STOP interval exceeds 100
nanoseconds or falls below 0 nanoseconds, the TI readings will necessarily wrap back
around to the opposite “rail.” This phenomenon gives rise to the sawtooth-shaped
phase trace familiar to users of vector network analyzers. As seen in the measurement
example above, the phase-wrapping effect is visible in the
Phase difference (Original)
( w ) measurement view in TimeLab.
Figure 18: Original phase data received from TIC (w) compared with unwrapped view (p)