3 Spectrum Analyzer Mode
3.13 Phase and Amplitude vs Time Measurement
where both low band and high band setups will follow in rapid succession. In this
path, the bypass of the low band/high band switch and microwave preamp is never
activated, which can cause some noise degradation but preserves the life of the
bypass switch.
For applications that utilize the wideband IF paths, the preset state is µW
Preselector Bypass, if option MPB is present. This is because, when using a
wideband IF such as the 140 MHz IF, the µW Preselector’s bandwidth can be
narrower than the available IF bandwidth, causing degraded amplitude flatness and
phase linearity, so it is desirable to bypass the preselector in the default case.
You may choose Low Noise Path Enable for a lower noise floor, especially in the 21-
26.5GHz region, though without improving many measures of dynamic range, and
without giving the best possible noise floor. The preamp, if purchased and used,
gives better noise floor than does Low Noise Path Enable, but the preamp’s
compression threshold and third-order intercept are much poorer than that of Low
Noise Path Enable.
A fourth choice is Full Bypass Enable, which combines µW Preselector Bypass and
Low Noise Path Enable. Because this can bypass most of the circuitry between the
input and the first mixer, care should be taken when using this setting to avoid
damaging the mixer. Full Bypass Enable is only available if both options LNP and
MPB are present, as well as option FBP.
Path Example Note
Standard Path :POW:MW:PATH
STD
Normal setting for most measurements. µW Preselector
in circuit, Low Noise Path disabled
Low Noise Path
Enable
:POW:MW:PATH
LNP
See "Low Noise Path Enable" on page 1988
µW Preselector
Bypass
:POW:MW:PATH
MPB
See "µW Preselector Bypass" on page 1990
Full Bypass
Enable
:POW:MW:PATH
FULL
See "Full Bypass Enable" on page 1990
Remote Command
[:SENSe]:POWer[:RF]:MW:PATH STD | LNPath | MPBypass | FULL
[:SENSe]:POWer[:RF]:MW:PATH?
Example
:POW:MW:PATH LNP
Enables the Low Noise path
:POW:MW:PATH?
Notes When "Presel Center" on page 1978 is performed, the instrument momentarily switches to the
Standard Path, regardless of the setting of µW Path Control
The DC Block will always be switched in when the low noise path is switched in, to protect succeeding
circuitry from DC. Note that this does not mean “when the low noise path is enabled” but when, based
on the Low Noise Path rules, the path is actually switched in. This can happen when the selection is
Low Noise Path Enable or Full Bypass Enable. In the case where the DC Block is switched in, the
instrument is now AC-coupled. However, if you selected DC coupling, the UI would still behave as
1984 Spectrum Analyzer Mode User's &Programmer's Reference
To Next Page
Loading...
