90 Chapter 4
Basic Digital Operation
Custom Modulation
Custom Modulation
For creating custom modulation, the signal generator offers two modes of operation: the Arb Waveform
Generator mode and the Real-Time I/Q Baseband mode. The Arb Waveform Generator 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. The Real-Time I/Q Baseband 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.
Custom Arb Waveform Generator
The signal generator’s Arb Waveform Generator 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 Waveform Generator 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 Waveform Generator 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 the sections “Using the Dual ARB Waveform Player” on page 106 and
“Modes of Operation” on page 24.
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