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72 Chapter 3
Basic Digital Operation
Arbitrary (ARB) Waveform File Headers
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 83 and
“Modes of Operation” on page 5.
Custom Real Time I/Q Baseband
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 I/Q Baseband 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.
For more information, refer to the custom arb section “Overview” on page 143, the custom real time
section “Overview” on page 165 and the section on “Digital Modulation” on page 6.
Arbitrary (ARB) Waveform File Headers
An ARB waveform file header enables you to save instrument setup information (key format settings)
along with a waveform. When you retrieve a stored waveform, the header information is applied so
that when the waveform starts playing, the dual ARB player is set up the same way each time.
Headers can also store a user-specified 32-character description of the waveform or sequence file.
A default header is automatically created whenever a waveform is generated, a waveform sequence is
created, or a waveform file is downloaded to the PSG (for details on downloading files, see the
E8257D/67D PSG Signal Generators Programming Guide).
The following signal generator settings are saved in a file header:
•ARB sample clock rate
• Runtime scaling (only in the dual ARB player)