TTI TGA1230, Руководство пользователя, Страница: 56 / 88

REF. CLOCK I/O SETUP
◊
input
◊
output phase…
◊
phase lock slave
Repeated presses of the
phase lock
soft-key toggle between
master
and
slave
.
The slaves are set to
slave
and the phase relationships between the slaves and the master are
set individually on the
SLAVE PHASE ANGLE
screens of each slave, accessed by pressing the
phase…
soft-key on the
REF. CLOCK I/O SETUP
above.
SLAVE PHASE ANGLE:
progrm: +000º
(actual: +000º)
done
◊
The phase angle is entered directly from the keyboard, or by using the rotary control, in the range
-360º to +360º. With all DDS waveforms (which comprise 4096 points) the actual phase angle will
be the same as the programmed angle. However, with arb waveforms, etc. which have less than
360 points per cycle the
actual
phase may differ from the
progrm
phase because of
insufficient resolution and is therefore displayed below the programmed value.
When the phase is set, pressing the
done
soft-key returns the display to the
REF CLOCK I/O
SETUP
screen. The convention adopted in Synchronised mode is that a negative phase setting
delays the slave output with respect to the master; for example, a phase setting of -90° will delay
the slave by a quarter-cycle with respect to the master. If the slave’s TRIG IN inputs are all driven
directly from the master then all phase shift is referenced from the master; thus 4 generators set
to the same frequency with the 3 slaves set to -90°, -180° and -270° respectively will give four
evenly spaced phases of the same signal. If, however, the synchronising signal was daisy-
chained from each SYNC OUT to the next generator’s TRIG IN then the phase shifts become
cumulative and each slave must be set to -90° phase to achieve the same result.
Hardware delays become increasingly significant as frequency increases causing additional
phase delay between the master and slaves. However, these delays can be largely nulled-out by
‘backing-off’ the phase settings of the slaves.
Synchronising
Having made the connections and set up the generators as described in the preceding
paragraphs, synchronisation is achieved by pressing the MAN/SYNC key of each slave in turn.
Once synchronised any change to the setup may require resynchronisation.
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