Bandwidth Coupling; Flexible Bandwidth Mode - Agilent Technologies 89410A Operator's Manual

Fundamental Measurement Interactions

Bandwidth coupling

Bandwidth coupling may be used to link resolution bandwidth and frequency span
in ways which are important to understand when setting up your measurement.
The automatic adjustment of resolution bandwidth to frequency span is called
"bandwidth coupling." It is an important feature and one common to most
spectrum analyzers.
For most measurement situations, the default bandwidth coupling type (auto)
provides the best compromise between frequency resolution and speed. And for
most measurements, bandwidth coupling is generally preferable since it simplifies
your measurement setup.
Changing bandwidth coupling
You can easily override the current resolution bandwidth selection by manually
entering a setting of your own. For example, you can specify a different resolution
bandwidth setting.
If you override a current resolution bandwidth setting, the analyzer remembers the
adjustment you made in terms of a resolution bandwidth to span ratio. It attempts
to maintain this ratio when calculating appropriate resolution bandwidth for
different spans. This is called offset coupling. For example, if you changed to a
narrower resolution bandwidth than the default (the resolution bandwidth selected
automatically), the analyzer maintains a narrower-than-normal resolution
bandwidth for subsequent spans. You can also specify this type of coupling by
selecting [ offset coupled ]. This type of coupling allows the response to appear the
same as the span is changed.
The other available coupling type is fixed coupling which maintains a resolution
bandwidth setting independent of other parameter changes. For example, this
allows you to change span without changing resolution bandwidth. Fixed coupling
is automatically selected if you explicitly alter the analyzer's time record length.

Flexible bandwidth mode

The 89400 series analyzers offers two levels of flexibility in selecting a resolution
bandwidth setting: 1-3-10 and arb. The first, 1-3-10, is the more restrictive. In this
x x
mode the analyzer always sets the resolution bandwidth at a 1 X 10 or 3 X 10
value. In this mode the analyzer emulates many existing spectrum analyzers. The
arb mode allows arbitrary setting of resolution bandwidth. Your choice of
bandwidth mode in conjunction with your choice of rbw coupling mode affects
both resolution and speed. To get the best resolution to speed tradoff, choose auto
rbw coupling and arb rbw mode.
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