Modulation Distortion Measurement Concepts; Purpose; Measurement Technique - Keysight X-Series Measurement Manual

Concepts

Modulation Distortion Measurement Concepts

Modulation Distortion Measurement Concepts

Purpose

This measurement is used to measure the amount of modulation distortion
contained in the modulated signal by determining the ratio of harmonic and
noise power to fundamental power. This measurement verifies the modulation
quality of the signal from the DUT.

Measurement Technique

Modulation Distortion is defined as:
Equation 2-4
First, the received signal is demodulated and filtered to remove DC. Then the
filtered signal is transformed by an FFT into the frequency domain. Next, total
power in the total filter band is measured as P
modulated signal is computed as P
P
signal
can be expressed as dB or %.
32
%
ModulationDistortion
where: P = the power of the total signal,
total
P = the power of the wanted modulating signal, and
signal
P - P = total unwanted signal which includes harmonic distortion
total signal
and noise.
to P is calculated. The result is the signal's modulation distortion. It
total
P P
–
total signal
- - - - - - - - - - - - - - - - - - - - - - - - - - - -
= ×
P
total
total
, the square root of the ratio of P
signal
Keysight N9063C Analog Demod Measurement Guide
100%
, the peak power of the
-
total