In-Channel Amplitude Modulation Interference - Agilent Technologies ESA-E Series User And Programming Manual

In-Channel Amplitude Modulation Interference

Many signals are present in an integrated communications system.
Examples may include digital, baseband, IF, and RF signals. Crosstalk
between adjacent components and stages often leads to unwanted
signals in the output. The Modulation Analysis Personality can help
identify these signals, including in-channel interfering tones that are
amplitude modulated.
For a Wideband CDMA signal, AM interference appears as an aligning
of the symbol decision points in the center of each quadrant, forming
"lines" of dots. This line extends farther outward as the magnitude of
the AM increases.
1. Use the I/Q polar constellation diagram first to identify this problem.
Press
Wideband CDMA signal with in-channel amplitude modulation
interference. Note the variation of amplitude around the ideal
symbol reference points. Also observe how much larger the
amplitude error values are compared to those for phase error in the
table.
The results shown were created with an amplitude modulation
deviation of 10% and a modulating frequency of 15 kHz.
Figure 4-29 Polar Constellation Showing AM Interference
Chapter 4
I/Q Measured Polar Constln
Making Modulation Analysis Measurements
Interpreting Measurement Results
. Figure 4-29 shows an example of a
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