Keysight CXG, EXG, and MXG X-Series Signal Generators Programming Guide 217
Creating and Downloading Waveform Files
Waveform Phase Continuity
Waveform Phase Continuity
Phase Discontinuity, Distortion, and Spectral Regrowth
The most common arbitrary waveform generation use case is to play back a
waveform that is finite in length and repeat it continuously. Although often
overlooked, a phase discontinuity between the end of a waveform and the
beginning of the next repetition can lead to periodic spectral regrowth and
distortion.
For example, the sampled sinewave segment in the following figure may have
been simulated in software or captured off the air and sampled. It is an
accurate sinewave for the time period it occupies, however the waveform does
not occupy an entire period of the sinewave or some multiple thereof.
Therefore, when repeatedly playing back the waveform by an arbitrary
waveform generator, a phase discontinuity is introduced at the transition point
between the beginning and the end of the waveform.
Repetitions with abrupt phase changes result in high frequency spectral
regrowth. In the case of playing back the sinewave samples, the phase
discontinuity produces a noticeable increase in distortion components in
addition to the line spectra normally representative of a single sinewave.
Sampled Sinewave with Phase Discontinuity
Waveform length
discontinuity
Phase
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