SCPI COMMAND SUMMARY
Frequency Subsystem
Anytwo frequency setting headers (STARt, STOP, CENTer, or
SPAN) may b e sent in a single message and the resulting sweep
is what was requested. The order of the headers in the message
does not makeany dierence in the nal result. When a message is
completed, coupling equations are used to x the unset parameters to
the correct values. These equations specify that:
center frequency = (start + stop) / 2
frequency span = (stop
0
start)
If more than two are sent, then the last two in the message are used
to determine the sweep and no errors are given.
If only one header is sent in a message, then the assumed pairs are
center/span and start/stop. In other words, if only center is sent,
then span is kept constant (if possible) while adjusting center to the
requested value. The start/stop frequencies are updated to reect the
changes based on the coupling equations.
The swept signal generator uses \bumping" to move unspecied
frequency parameters, but if the nal value of any of the frequency
headers is the result of bumping, then an error is generated since
the user is
not
getting what was specied. This means, to guarantee
sequence independence requires sending the frequency pairs in a
single message.
Example 1: (present state start = 5 GHz, stop = 6 GHz)
FREQ:STARt 20 GHZ
an error results since the
stop frequency is bumped.
FREQ:STOP 22 GHZ
the nal sweep does not
generate an error
(20 to 22).
Example 2: (present state start = 5 GHz, stop = 6 GHz)
FREQ:STOP 22 GHZ
no error is generated,
start frequency is unchanged.
FREQ:STARt 20 GHZ
stil l no error.
Example 3: (present state start = 5 GHz stop = 6 GHz)
FREQ:STARt 20 GHZ;STOP 22 GHZ
both are ne,
FREQ:STOP 22 GHZ;STARt 20 GHZ
no errors.
FREQuency:CENTer <num>[freq
suffix]|MAXimum|MINimum|UP|DOWN
FREQuency:CENTer? [MAXimum|MINimum]
Sets and queries the center frequency.
The *RST value is (MAX + MIN)/2.
FREQuency[:CW|:FIXed] <num>[freq
suffix]|MAXimum|MINimum|UP|DOWN
FREQuency[:CW]? [MAXimum|MINimum]
FREQuency[:FIXed]? [MAXimum|MINimum]
Operating and Programming Reference S-35
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