Functions and Measurements
Making Distortion Measurements
52
Notice the MarkerD amplitude readout. This is the difference
of the distortion product amplitude between 0 dB and 10 dB
input attenuation settings. If the MarkerΔ absolute amplitude
is approximately 1 dB for an input attenuator change, the
analyzer is generating, at least in part, the distortion.
The MarkerΔ amplitude readout comes from two sources:
1) Increased input attenuation causes poorer signal- to- noise
ratio. This causes the MarkerΔ to be positive.
2) The reduced contribution of the analyzer circuits to the
harmonic measurement causes the MarkerΔ to be negative.
Large MarkerΔ readout indicates significant measurement
errors. Set the input attenuator to minimize the absolute
value of MarkerΔ.
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