Agilent Technologies PSA Series Manual page 300

Concepts
Analog Modulation 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 UUT.
Measurement Technique
Modulation Distortion is defined as:
Equation 5-3
%
where: P
P
P
noise.
See Figure 5-11 on page
to remove DC, then the filtered signal is transformed by an FFT into frequency
domain. Next, total power in the total filter band is measured as P
power of the modulated signal is computed as P
P
total
can be expressed as dB or %.
300
=
ModulationDistortion
= the power of the total signal,
total
= the power of the wanted modulating signal, and
signal
− P
= total unwanted signal which includes harmonic distortion and
total signal
299. First, the received signal is demodulated and filtered
− P
to P is calculated. The result is signal's modulation distortion. It
signal total
P – P
total signal ×
---------------------------------- - 100%
P
total
, the square root of the ratio of
signal
, the peak
total
Chapter 5