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7
Chapter 7 Tutorial
Signal Imperfections
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Pulse Waveform Parameters
Signal Imperfections
For sine waveforms, signal imperfections are easiest to describe and
observe in the frequency domain using a spectrum analyzer.
Any component of the output signal which has a different frequency
than the fundamental (or "carrier") is considered to be spurious.
The signal imperfections can be categorized as harmonic, non-harmonic,
or phase noise and are specified in "decibels relative to the carrier level"
or "dBc".
Harmonic Imperfections
Harmonic components always appear at multiples of the fundamental
frequency and are created by non-linearities in the waveform DAC and
other elements of the signal path. At low amplitudes, another possible
source of harmonic distortion is due to the current flowing through the
cable connected to the function generator's Sync output connector.
This current can cause a small square-wave voltage drop across the
resistance of the cable's shield and some of this voltage can be imposed
on the main signal. If this is a concern for your application, you should
remove the cable or disable the Sync output connector. If your application
requires that you use the Sync output connector, you can minimize the
effect by terminating the cable in a high impedance load (rather than into
a 50Ω load).
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Fall Time
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