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SECTlON 3
Operation
hold mode. In the sweep execution
mode, the Model
3930A halts the sweep as long as this input remains low.
If you attempt to start a sweep when this input is low, the
Model 3930A immediately
enters the sweep hold mode.
Note
that pressing
HOLD/RESM
does not resume
sweep operation with the hold signal held low; you must
set SWEEP HOLD IN high to resume the sweep.
SWEEP HOLD IN is internally
pulled up to a high logic
level, and sweep operation is not affected when this con-
nector is left disconnected
from external signals.
Sweep Frequency and Sweep Output
Figure 3-14 illustrates
how the sweep frequency and the
MKR OUT, SWEEP SYNC OUT, and X DRIVE OUT sig-
nals change with time.
The MKR OUT signal is high when the sweep frequency
is higher than the marker frequency.
When the sweep
function
is n
or 1,
the high signal level is maintained
even after a single sweep is terminated.
The SWEEP SYNC OUT signal goes low during the tran-
sition from the start frequency
to the stop tiequency.
When the sweep function is 1,
the frequency changes at
the center point of this output signal.
The X DRIVE OUT jack supplies a voltage that varies be-
tween OV and 1OV in proportion
to the lapse of sweep
time, and according
to the direction
of the sweep fre-
quency. The X DRIVE OUT signal also varies linearly
with time in the log sweep or step sweep mode.
Substituting
Marker Frequency for Center Frequency
Press SHIFT CTRI
to set the center frequency to the cur-
rent marker frequency
value. This operation
produces
the same result as programming
an identical frequency
with the numeric keys. The marker frequency is not af-
fected by this operation.
Changing
Settings During
Sweep Operation
Because of processing execution time in the sweep execu-
tionmode,
theModel3930Amayrespond
to the keys and
GPIB commands mcze slowly in the sweep mode than in
other modes. If you change the sweep range, sweep time,
or sweep function with MODIFY while the Model 3930A
is in the sweep execution mode, the unit will recalculate
the new parameters each time you change the setting, re-
sulting in slower response.
If you set the sweep range based on center and span fre-
quencies, an error may occur depending
on the order of
parameter selection whether or not the Model 3930A is in
the sweep execution mode.
Example:
To change a SkHz center frequency and an &Hz span fre-
quency to 2kHz and 3kHz respectively,
you must first
change the span frequency to 3kHz and then change the
center frequency to 2kHz. If you first change the center
frequency to &Hz, an error will occur because this com-
bination would result in a start frequency of -2kHz.
Number of Steps in a Sweep
Sweep operation
of the Model 3930A is controlled
by
software. The software determines the number of steps in
a sweep (excluding
step sweep) so that the Model 3930A
can perform as smooth a sweep as possible, considering
the processing speed of the microprocessor
and the reso-
lution of the synthesizer
(O.lmHz).
The number of steps in sweep can be roughly
calculated
as outlined below. The number of steps described here is
the number of steps between the start frequency and the
stop frequency when the sweep function 1s ANA.
Linear sweep steps
Inalinearsweep,
thenumberof
stepscanbecalculated
as
follows:
Number of steps: [Sweep width (Hz) x 10'1 or
[Sweep time (SK) x 20001, whichever
is greater.
3-33
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