Rohde & Schwarz R&S UPP, User Manual

Page: 573 / 938

Instrument Functions
R&S
®
UPP
557 User Manual 1411.1055.32 ─ 10
Application: Constant (i.e. frequency response independent) power output, preempha-
sis/deemphasis.
If there is no check in the box, the equalization data set that is acquired corresponds to
the frequency response of the DUT.
If the DUT is removed and a generator sweep is carried out using this equalization
data set, the DUT can be simulated since a frequency response arises as if the DUT
were present.
Remote command:
MMEMory:SWEep<n2>:EQUalization:INVert
on page 803
Modify Equ.
This is offered for "Store Trace as " = "Equalization List ".
The current generator equalization data set is taken into account when the new equali-
zation list is stored in order to obtain a significantly more accurate precorrection.
What is the purpose of multistage preemphasis?
Example:
At high frequencies a loudspeaker frequency response has a roll-off of approx. 10 dB.
The intention is to compensate the frequency response by means of a generator pre-
emphasis (equalization). For this purpose a generator sweep is started and the fre-
quency response curve is acquired. An equalization file is created from this trace and
made available to the generator. Another sweep is started using the equalization file
and the frequency response is acquired.
The frequency response now seems considerably better, though the expected straight
line has not appeared and there are inaccuracies in regions showing greater generator
level increases.
The causes for this are
non-linearities in the loudspeaker system. An increase in the
generator level of 10 dB has not, as first expected, also increased the loudspeaker
sound pressure by 10
dB but rather by only (for example) 9.8 dB due to non-linearities.
In order to compensate for these inaccuracies a further equalization using "Modify Equ.
" can be performed. This second scan, based on the data set of the equalization file
loaded in the generator, usually produces the expected flat frequency response.
If "Modify Equ. " is enabled and a new equalization file is created but equalization is
not yet enabled in the generator, equalization is turned on by default using the newly
created file name.
Remote command:
MMEMory:SWEep<n2>:EQUalization:MODify
on page 803
Offset
This is offered for "Store Trace as " = "Limit List ".
Curve, Spectrum and Bar Graph Display