Symmetry
For both triangular and sinc waveforms, it marks the location as a percentage of
the positive highest peak within a period of the basic signal.
Sinc Length
The number of zero crossings in a single period for the sinc waveform type.
Crest Factor
The peak-to-average power ratio in dBs for Noise samples before low-pass
filtering. Ideally, Gaussian noise is not bounded, so the crest factor keeps growing
(up to infinity) as the observation time window grows. This cannot be supported by
AWG generated noise, because waveform length and dynamic range are limited.
The higher the peak the lower the average power for that noise will be, if the full
waveform excursion must fit the available DAC range. The user can select the
maximum amplitude of the unfiltered noise relative to the average power (or rms
amplitude). When the noise amplitude is bigger than the user-set limit, the
waveform is clipped. The actual crest factor will be higher than expected as
bandwidth limiting filtering will create some samples beyond the user-set limits.
Clipping is applied before filtering to avoid a very noticeable spectral growth.
Noise Bandwidth
Baseband noise bandwidth for Noise waveforms. Spectral density for the noise will
be flat up to the frequency set by this parameter. This is accomplished by applying
near ideal low-pass filtering to the unfiltered noise (random samples with a
Gaussian distribution sampled at the DAC Sample Rate). For IQ modes, noise
bandwidth around the carrier frequency will be twice this parameter.
Additional Waveform Parameters Section
Preamble Length
The duration of a DC section before the defined Standard waveform starts.
Preamble Level
The level for the DC section before the defined Standard waveform starts.
Acceptable range for this parameter is -1/+1, being the full dynamic range of the
instrument’ DAC.
Postamble Length
The duration of a DC section after the defined Standard waveform stops.
Postamble Level
The level for the DC section after the defined Standard waveform stops. Acceptable
range for this parameter is -1/+1, being the full dynamic range of the instrument’
DAC.
Keep Periods
This checkbox is only available when “Keep Sample Rate” is selected. When this
option is selected, the waveform calculation algorithm preserves the user-defined
number of periods.
Periods
The number of repetition of single periods of the standard waveform within the
target segment. This parameter is set automatically when Frequency is changed
and preamble and postamble lengths are set to zero in order to obtain the best
timing accuracy and meet the record length granularity requirements.
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