Keysight EXG and MXG X-Series Signal Generators User’s Guide
263
Basic Digital Operation (Option 653/655/656/657)
Setting the Real-Time Modulation Filter
Setting the Real-Time Modulation Filter
The real-time modulation filter effectively compresses a single carrier I/Q waveform down to just
the I/Q constellation points and then controls the transitions similar to the modulation filter in Arb
Custom modulation. The key difference is that this filter is applied as the waveform plays, rather
than in the waveform data itself. The real-time modulation filter is only available for Dual ARB
waveforms.
When the real-time modulation filter is on, the sample clock rate acts as the symbol rate. The
sample clock rate must be set to one half of the sample rate for the real-time Arb modulation filter
feature to be turned on. The sample rate is determined by the Option 65x baseband generator.
Figure 9-26
Real-Time Modulation Filter Softkeys for the Dual ARB Player
Common uses for the real-time modulation feature include:
— Where the single carrier rectangular ideal I/Q symbol decision points are known and are to have
an over-sampled filter applied.
— Where greater effective MXG/EXG memory size is required.
Because the Arb format only supports rectangular I/Q data for defining the
symbol decision points, constant envelope modulation, which should be
specified as magnitude and phase, are not supported. (Examples of
constant envelope modulation are MSK and FSK.)
The carrier frequency must be the same for all frequencies used (i.e. only
single carrier applications work with arb real-time modulation filters).
The settings in this menu
can be stored to the file
header, see
.
For details on each key, use key help
.
Mode > Dual ARB > Arb
Setup > More
These are the available
real-time modulation filters that
can be applied to a waveform.
