Tektronix Tektronix SPG8000, Техническое описание

Страница: 31 / 118

Speci fi cations
Table 27: GPS timebase (cont.)
Characteristic Performance requirements Reference information
Stability when locked to GPS or
GLONASS (typical)
1
Allan Deviation < 8 x 10
–11
, measurement
interval of 1, 10, or 100 sec in fi xed position
mode.
Note that this is for fi xed mode and is a
function of base unit oscillator, satellite signal
quality from antenna, and GPS functionality.
For mobile mode, the Allan deviation is about
2 x 10
-10
.
Accuracy when locked to GPS or
GLONASS
1
±1 part in 10
9
averaged over 30 sec. After
20 min warm up and in fi xed mode.
Long term stability is set by the GPS, but
short term by the base unit.
Accuracy in Holdover mode
(typical)
±2 parts in 10
9
from recent valid lock
frequency, Temp change of ±5 °C.
±10 parts in 10
9
for 0 to 50 °C.
Translates to 10 ns of drift per 1 sec that is
in holdover mode. This is a function of the
base unit oscillator.
Clean Recovery Holdover Drift
(GPS mode only)
±20 ms
Maximum amount of timebase drift that can
be corrected without disruption to video
timing.
Clean Recovery Holdover Duration
(typical)
(GPS mode only) 35 days, must be in stable temperature
environment and have warmed up for
20 minutes before holdover. Length of time that can be in stay current
holdover mode and recover without disruption
to syncs. Dependant on environment and
base unit oven oscillator stability. Translates
to 2 ns of drift per sec in holdover mode.
Timing behavior when locked
(GPS mode only) Displays “Locked” if within 150 ns of absolute
time as detected by GPS or GLONASS
signal.
Frame Timing Accuracy in fi xed
position mode (typical)
(GPS mode only)
Outputs of any two units are typically timed
within 150 ns if both have good signal quality
and the same cable delay from antenna to
instrument. Frames Based on SMPTE 404 / TAI Epoch
Frame behavior on Relock (typical)
(GPS mode only) Selectable between Jam Phase, Fast Slew
and Stay Legal.
In Stay Legal mode, will stay in spec as slew
with respect to frequency offset and drift
rate spec. If in fast slew or stay legal mode,
frames will slew back to the correct alignment
via timebase offset without jumping. Recovery from drift may take a long
time if con
fi gured for stay legal recovery
(approximately 300 sec per line of drift at
NTSC or PAL rates).
Timebase offset during Relock
(typical)
(GPS mode only) For stay legal mode, limited to less than
±0.2 ppm frequency offset, and limited to
change less than 0.02 ppm/sec. Fast Slew has limits of ±5 ppm offset and
0.5 ppm / sec.
SPG8000 Speci fi cations and Performance Veri fi cation 17