Keysight EXG and MXG X-Series Signal Generators User’s Guide 257
Using Custom Digital Modulation for N5172B/82B with Option 431 and 653/655/656/657
Using ARB Custom Modulation Softkeys
ARB Custom Modulation Mode
The ARB Custom Modulation mode has built-in modulation formats such as NADC or GSM and
pre-defined modulation types such as BPSK and 16QAM that can be used to create a signal. It also
provides the flexibility to modify the digital format’s attributes. This mode is designed for out–of–
channel test applications and can be used to generate data formats that simulate random
communication traffic and can be used as a stimulus for component testing. Other capabilities of
this mode include:
— configuring single or multicarrier signals. Up to 100 carriers can be configured.
— creating waveform files using the signal generator’s front panel interface.
The waveform files, when created as random data, can be used as a stimulus for component testing
where device performance such as adjacent channel power (ACP) can be measured. The
AUTOGEN_WAVEFORM file, that is automatically created when you turn the ARB Custom Modulation
on, can be renamed and stored in the signal generator’s non–volatile memory. This file can later be
loaded into volatile memory and played using the dual ARB waveform player.
For more information, refer to “Waveform Files (Segments and Sequences)” on page 153 and
“Modes of Operation” on page 52.
Real-Time Custom Modulation Mode
This mode can be used to create custom data formats using built-in PN sequences or custom-user
files along with various modulation types and different built-in filters such as Gaussian or Nyquist.
The real-time mode simulates single-channel communication using user-defined modulation types
along with custom FIR filters, and symbol rates. Data can be downloaded from an external source
into PRAM memory or supplied as real-time data using an external input. The real-time I/Q
baseband mode can also generate pre-defined data formats such as PN9 or FIX4. A continuous
data stream generated in this mode can be used for receiver bit error analysis. This mode is limited
to a single carrier. The real-time custom modulation mode:
— has more data and modulation types available than the ARB waveform generator mode
—supports custom I/Q constellation formats
— has the capability to generate continuous PN sequences for bit error rate testing (BERT)
— needs no waveform build time when signal parameters are changed.
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