Waveform Frequency
Repetition rate for one cycle of the standard waveform. It is always a positive
number except when Signal Type is set to Sine and the Generate I/Q Data
checkbox is checked. In this case, frequency may be negative so the resulting
SSB (Single-Side Band) will be located over or below the carrier frequency.
If the Waveform Type Noise is selected, this parameter is the repetition
frequency of a waveform consisting of pseudo-random samples with a near
Gaussian distribution. The spectrum for the generated noise will not be
continuous as it would be for a true Gaussian distribution, because it is made
of discrete tones with a spacing equal to the repetition frequency. This can be
observed by performing spectrum analysis with a sufficiently low resolution
bandwidth. By controlling the repetition frequency, the user can optimize
noise usability for a particular situation saving both waveform memory and
calculation time.
Initial Phase
The phase within a normalized cycle of the standard waveform for the first
sample in the segment.
Duty Cycle
The relative width as a percentage of the mark and the space sections of
square waves.
Rise Time
The transition time (10%-90%) for the rising edge in square waveforms.
Fall Time
The transition time (10%-90%) for the falling edge in square waveforms.
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.
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