User`s manual

[SOURce:]FREQuency[1]
The [SOURce:]FREQuency[1] subsystem controls the first of the Agilent E1445A’s
two frequency generators. (
[SOURce:]FREQuency2 controls the second generator.)
The first generator uses a direct digital synthesis (NCO) technique to generate the
specified frequencies. It has an upper frequency limit of the reference oscillator
frequency divided by 4 (the second generator operates up to the reference oscillator
frequency). This generator has excellent resolution (.01 Hz with the 42.94 MHz
reference oscillator) and allows frequency sweeping. Sine wave output is possible
only with this generator. The second generator has better phase noise characteristics
and permits higher frequency operation.
The values programmed by this subsystem are only used when
TRIGger[:STARt]:SOURce is set to INTernal1.
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, FREQuency1:CENTer MINimum
would set 500 kHz.
The minimum possible frequency is 0 Hz, except in the case of logarithmic
frequency sweeps. For logarithmic frequency sweeps, the minimum frequency is
the maximum possible frequency divided by 1,073,741,824. The maximum
possible frequency depends on the frequency of the currently selected reference
oscillator source (
[SOURce:]ROSCillator:SOURce), the waveform shape
[SOURce:]FREQuency[1]
Chapter 8 Command Reference 319