Tektronix TG700, Руководство пользователя

Страница: 216 / 343

GPS7 GPS Synchronization and Timecode Module
Table 3-17: Figures of merit for signal quality (cont.)
Figure
of merit
(FOM)
Indicator Description
3 Bad position This means that the instrument detects that
the stored position is different from the current
position. In this case, the instrument will
automatically go to FOM state 4 and reacquire
the position.
4 Acquire position This means that the instrument is acquiring
multiple
fi xes of the satellite position and
averaging this into a new position to store in
fl ash. This state will also be displayed if you
manually perform a new position acquisition.
This state normally lasts 60 seconds with good
GPS signal quality.
5 Adjust phase This means that the instrument is adjusting the
time base or frame timing to correctly line up
with the GPS signal.
6 Locked >
Signal quality is
≤ 16
7
Locked >>
Signal quality is > 16
8 Locked >>>
Signal quality is > 26
9 Locked >>>>
Signal quality is > 42
10 Locked >>>>>
Signal quality is > 68
11 Locked >>>>>>
Signal quality is > 110
These states indicate that the phase of the
frame signals is within 150 ns of the GPS
signal. The number of arrows indicates the
signal quality. It is normal for this to vary with
the time of day as the different satellites move
through their orbits, as well as with changes in
weather and other conditions.
NOTE.
The duration of some states depends on the strength of the received GPS
signal. If the antenna only has access to part of the sky, or if the cable loss
between the antenna and the receiver is too large, then it may take signi
fi cantly
longer to progress up to the higher entries in the FOM table.
Time Flow Block Diagram
The following time fl ow diagram shows time information is used at different
points in the system. In particular, it illustrates how the different user inputs and
con
fi guration settings combine with the time base to create the timecode. An
asterisk (*) denotes points of possible user input.
3–104 TG700 TV Signal Generator Platform User Manual