154 Chapter 4
Downloading and Using Files
Downloading ARB Waveform Data
Data Requirements and Limitations
• Data must be in signed, 2’s complement (binary) format.
• Data must be in 2-byte integers.
Two bytes are needed to express 16-bit waveforms. The signal generator accepts the MSB first, LSB
last.
• Input integers must be between −32768 and 32767.
This range is based on the input specifications of the 16-bit DAC used to create the analog voltages for
the I/Q modulator.
• 0 = 0 volts
• –32768 gives negative full-scale output
• 32767 gives positive full-scale output
• Each I/Q waveform must contain at least 60 samples to play in the waveform sequencer (one sample
equals one pair of I/Q values and markers). If this requirement is not met, the signal analyzer displays:
“File format invalid.” The file format is discussed in greater detail in the following sections.
If a waveform file is too large to fit into a 1024-byte memory segment, additional memory space is
allocated in multiples of 1024 bytes. For example, a waveform represented by 500 samples is allocated
to a 2048-byte memory segment (500 samples x 4 bytes); a 60 sample waveform file occupies 1024
bytes of waveform memory.
Total memory usage may be much more than the sum of the samples that make up waveform files; many
small waveform files can use large amounts of memory.
• Each I/Q waveform must contain an even number of samples to play in the waveform sequencer. If this
requirement is not met, the signal analyzer displays: “File format invalid.”
• A marker file is always associated with an I/Q waveform file. An empty (all zeros) default marker file is
created if a marker file is not provided by the user.
NOTE The default marker file is automatically created when the I/Q waveform file is loaded into
volatile WFM1 (waveform memory) prior to playing. If the default marker file is used,
toggle the Mrk 2 to RF Blank softkey to off.
• The user-defined marker file and I/Q waveform data file must have the same name in the signal
generator.
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