318
Chapter 7 Tutorial
Signal Imperfections
7
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).
Rise Time Fall Time
10%
90%
0%
10%
90%
50%
Pulse Width
Period
33210A users guide.book Page 318 Wednesday, July 16, 2008 11:16 AM
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