3 Short-Range Comms & IoT Mode
3.12 Monitor Spectrum Measurement
1.
If the measurement supports EMC Standard, and the detector is Peak and the
EMC Standard is set to either CISPR or MIL, use 10.0 (we use wide VBWs to
capture peak levels accurately).
2.
Otherwise, if the detector is Negative Peak, use 1.0 (in the Negative Peak case,
there are no known significant use models so we use a medium ratio).
3.
Otherwise, if the detector is Normal, use 1.0.
4.
Otherwise, if the detector is Average, and the span is nonzero, use 0.1. The use of
a small ratio in Average detection is desirable because of its effect on the sweep
time equations. The VBW filter is not actually in-circuit when the average
detector is on. If the detector is Average, and the span is zero, use 10.0, which
gives optimal behavior for Interval Markers in zero span. Note that only the
Swept SA measurement supports Zero Span.
5.
Otherwise, if the detector is EMI Average, Quasi Peak or RMS Average, use 10.0.
In fact, this is a “don’t care” since no VBW is used for these detectors, as noted
under “Dependencies” for the VBW control
6.
Otherwise, the detector is simply Peak or Sample. These two detectors can use
the same rules. In these cases, if any active trace is in max hold or min hold, use
10.0, because Max and Min Hold operations will usually be intended to capture
peaks and pits without smoothing from the VBW filter; otherwise, use 1.0 as a
compromise, because you have not set the instrument in a way that implies that
you are measuring noise, pulsed-RF or CW signals, and for backward
compatibility with earlier instruments.
Note that because the above couplings depend on which traces are active, they are
re-examined whenever any trace goes active or inactive, except when this leaves no
traces active. Transitioning to the state where no traces are active should not affect
the couplings; in that way, the annotation will always reflect the state of the last
trace which was active.
Note also that some detectors are not available in some measurements, but
because of the way the above rules that does not change the logic of the rules.
Span:3dB RBW
Selects the ratio between span and resolution bandwidth.
Normally, Span:3dB RBW (Auto) selects a Span:3 dB RBW ratio of 106:1. If you
manually enter the ratio, the toggle on the Span:3dB RBW control will change to
Man. This enables you to manually select ratios more suitable for certain
measurements.
1678 Short Range Comms & IoT Mode User's &Programmer's Reference
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