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Keysight EXG and MXG X-Series Signal Generators User’s Guide
Custom Digital Modulation (Option 431)
Custom Modulation
Custom Modulation
For creating custom modulation, the signal generator offers two modes of operation: the ARB
custom modulation mode and the real-time 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. The real-time custom modulation 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.
Both modes of operation are used to build complex, digitally modulated signals that simulate
communication standards with the flexibility to modify existing digital formats, define or create
digitally modulated signals, and add signal impairments.
ARB Custom Modulation Waveform Generator
The signal generator’s ARB Custom Modulation mode is designed for out–of–channel test
applications. This mode 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
the ARB Custom Modulation 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 File Basics” on page 187
and
.
Real-Time Custom Modulation Waveform Generator
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.
