R&S SMB100A, Operating Manual

Page: 187 / 528

Instrument Function
R&S
®
SMB100A
172 Operating Manual 1407.0806.32 ─ 21
The filter length can be selected automatically or can be manually set to a fixed value.
As a preliminary, you should always check if the auto mode is giving satisfactory
results because you will always have to adjust an optimal, manual filter-length setting if
the power is not constant.
Selection "Fixed Noise" is offered for achieving defined measurement accuracy.
"Auto" The filter length is automatically selected and adapted to the currently
measured value. With very high signals the filter length and therefore
the measurement time can be short. With very low signal levels the
filter length and therefore the measurement time is increased in order
to reduce noise. The used filter length is indicated in the field to the
right, see
Filter Length .
"User" The filter length is set manually.
The filter length is entered in the entry window to the right. As the fil-
ter length works as a multiplier for the time window, this results in a
constant measurement time.
Note: The time window varies depending on the used sensor. For
most sensors it is fixed to 20 ms. For the R&S NRP-Z81 sensor it is
10 us. Therefore, the user filter length for the R&S NRP-Z81 has be
about 1000 times larger than the filter length for other sensors in
order to achieve the same filtering result.
The
Auto Once button can be used to search for the optimum filter
length for the current measurement conditions. The found filter length
is indicated in the field to the right, see
Filter Length .
"Fixed Noise" The averaging factor is selected so that the sensors intrinsic noise (2
standard deviations) does not exceed the specified noise content.
The desired noise content is entered in the entry field to the right, see
Noise Content .
To avoid very long settling times when the power is low, the averag-
ing factor can be limited with the
Timeout parameter.
Remote command:
:SENSe<ch>[:POWer]:FILTer:TYPE
on page 320
Filter Length ← Filter
Indicates the used filter length for filter type "Auto" or "User".
Remote command:
:SENSe<ch>[:POWer]:FILTer:LENGth:AUTO?
on page 318
:SENSe<ch>[:POWer]:FILTer:LENGth[:USER]
on page 319
Noise Content ← Filter
Sets the noise content for filter type "Fixed Noise".
Remote command:
:SENSe<ch>[:POWer]:FILTer:NSRatio
on page 319
Timeout ← Filter
Sets a time limit for the averaging process.
Remote command:
:SENSe<ch>[:POWer]:FILTer:NSRatio:MTIMe
on page 320
RF Block