Rohde & Schwarz SMM100A, User Manual

Page: 237 / 1088

Configuring the internal baseband source
R&S
®
SMM100A
237 User Manual 1179.1341.02 ─ 05
When the cutoff frequency is set as half of the output sample rate, a final lowpass filter
improves the spectrum of the clipped multicarrier signal. This process can increase the
resulting crest factor. See also
Chapter 4.10.2.2, "Optimizing the crest factor" ,
on page 233.
Remote command:
[:SOURce<hw>]:BB:ARBitrary:MCARrier:CLIPping:CUToff
on page 825
Signal Period Mode
Defines the way the resulting signal period of the multi-carrier waveform is calculated.
The resulting period is always calculated for all carriers in the carrier table irrespective
of their state (ON/OFF). Use the "Carrier Table > Info" function to obtain information on
the sample rate and file length data of each carrier.
Note: Wrap-around and timing problems can occur when I/Q signals of different length
are used. Thus, demodulation of a carrier can be difficult or even impossible.
We recommend that you proceed as follows:
●
Consider the timing when creating the input I/Q files.
●
Adjust the signal duration to the carrier which is then demodulated.
(In this case, the other carriers are for interfering the signal only.)
These problems do not arise with signals of the same standard (e.g. 3GPP).
The following modes are available:
"Longest File Wins"
The longest I/Q file in the carrier table defines the resulting signal
period. Shorter I/Q files are periodically repeated.
"Shortest File Wins"
The shortest I/Q file in the carrier table defines the resulting signal
period. Only the first part of longer I/Q files is used.
"User" The signal period is set manually ( Signal Period ). Shorter I/Q files are
repeated periodically, and only the first part of longer I/Q files is used.
"Least Common Multiple"
The output file duration is the least common multiple of all input file
durations.
Remote command:
[:SOURce<hw>]:BB:ARBitrary:MCARrier:TIME:MODE
on page 826
Signal Period
Sets the signal period in signal duration mode "User". Shorter I/Q files are repeated
periodically, and only the first part of longer I/Q files is used.
Remote command:
[:SOURce<hw>]:BB:ARBitrary:MCARrier:TIME
on page 824
Power Reference
Defines the way the individual carriers in a composed multi carrier signal are leveled.
The difference between the provided modes is especially important if signals with dif-
ferent crest factors are composed together into a multi carrier signal.
Generating multi-carrier signals