Keysight B Series - Page 185

Keysight N9938-90003 User’s Guide 185
SA (Spectrum Analyzer) Mode (Option 233–Mixed Analyzers)
Spectrum Emission Mask (SEM) — (SA Mode Only)
— Ofst Enable Enables/disables the currently selected
Frequency Start/Stop Offset values.
— Ofst Freq Start
Sets the offset frequency start value.
(Default/Maximum = Value varies with model and options,
Minimum = 0 Hz).
— Ofst Freq Stop
Sets the offset frequency stop value.
(Default/Maximum = Value varies with model and options,
Minimum = 0 Hz).
— Res BW
Auto/Manual (Default is Auto). Sets the current
resolution bandwidth value. See also, “Resolution
Bandwidth (Res BW)” on page 128.
— Offset Side Neg Both Pos
(Default is Both). Sets the offset
side measurement value. Select Negative (Neg) to
measure the negative side of the spectrum. Select Positive
to measure the positive side of the spectrum.
— Offset Freq Def
then select one of the following:
— Carrier Center
(Default) applies the frequency offsets to
the current carrier center frequency.
— Carrier Edge
Selects the edge of the carrier for frequency
offset definition.
— Power Ref
– the reference power value can be fixed (which also
fixes the Relative Limit line), but the user must then consider the
unit being used (dBm or dBm/Hz) depending on the Meas Type
selected. If Power Ref is left AUTO (Default) then its value will track
the Meas Type and change units automatically. Both fixed and Auto
settings display the power reference value measured.
3. Setting Center Frequency and Span
Press Freq/Dist then
— Center
- sets the center frequency.
— SEM Auto Span
- Enables/disables the SEM Auto Span.
— Freq Span
- sets the frequency span of the SEM measurement.
Frequency control menu (Center and Span) provides an SEM Auto Span
control (defaulted to ON) which automatically tracks the necessary span to
cover all enabled offset segments. In the example in Figure 7-20 on
page 183, the necessary span is 16 MHz. But the you can de-couple the
span simply by narrowing or widening Span it in order to zoom.
The Carrier Frequency (Ref Channel Center) by default tracks the specified
Center Frequency, but can be forced to "Hold" at a particular location
which would then allow the user Center Frequency to pan above or below
for reasons similar to zooming with span.