HP E1340A User's Manual
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[SOURce:]FREQuency
The [SOURce:]FREQuency subsystem controls the HP E1340A’s frequency
generator.
The generator uses a direct digital synthesis (NCO) technique to generate
the specified frequencies. It has an upper frequency limit of the reference
oscillator frequency multiplied by .468749999767 and has a resolution of
.01 Hz when used with the built-in 42.94 MHz reference oscillator.
Coupling Rules The swept commands STARt, STOP, CENTer, and SPAN are coupled
commands. When sending these commands, the following rules apply:
• If either STARt or STOP is sent singly, the value of the other is
preserved, but the
CENTer and SPAN values will change according
to the following equations:
CENTer= (STARt + STOP)/2
SPAN = STOP - STARt
• If either CENTer or SPAN is sent singly, the value of the other is
preserved, but the
STARt and STOP values will change according to
the following equations:
STARt = CENTer - (SPAN/2)
STOP = CENTer + (SPAN/2)
• If any two commands are sent as part of a frequency-coupled group
within a single program message, then these two will be set as
specified, and the other two will change. If more than two are sent in
the group, the sweep will be determined by the last two received.
When
MINimum and MAXimum are used with these commands, the values
that will be set are the minimum and maximum values that will not cause
any of the
STARt, STOP, CENTer, and SPAN values to go beyond the
minimum and maximum possible frequencies, given the coupling equations
above. For example, if
SPAN is currently set to 1 MHz,
FREQuency:CENTer MINimum would set 500 kHz. An exception to this
rule exists, however: since the minimum
SPAN is .01 Hz per sweep point
(assuming the internal reference oscillator), a command string such as
FREQuency:CENTer 0;SPAN MINimum has no valid value for SPAN, and
will attempt to set the
STARt frequency to a negative value. Similarly,
FREQuency:STARt 15e6;STOP MINimum will attempt to set STOP to
value greater than 15 MHz.
[SOURce:]FREQuency:DOWNload :COMPlete
Chapter 7 HP E1340A Command Reference 153