In-Channel Spurious Signal Interference - Agilent Technologies ESA-E Series User And Programming Manual

In-Channel Spurious Signal 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 spurious signals.
For a Wideband CDMA signal, an in-channel spurious signal appears
as circular-shaped donut groupings of symbol decision points in each of
the quadrants. This is because the spur modulates both the amplitude
and phase of the I and Q signals. If the signal is modulated only without
spurious interference, there will be no holes in the circles; this also
indicates a poor signal-to-noise ratio. The donut size diameter increases
as the magnitude of the spur increases.
1. Figure 4-33
+ 400 kHz away from the unmodulated radio signal. Even a large
interfering signal such as this is barely visible in the spectrum view,
even with averaging on.
Figure 4-33 Spectrum Display Showing In-Channel Spurious Interference
Chapter 4
Making Modulation Analysis Measurements
shows an in-channel spurious signal that is –15 dBc and
Interpreting Measurement Results
53