Keysight N9063C Analog Demod Measurement Guide 33
Concepts
Modulation SINAD Measurement Concepts
Modulation SINAD Measurement Concepts
Purpose
Modulation SINAD (SIgnal to Noise And Distortion) measures the amount of
Modulation SINAD contained in the modulated signal by determining the ratio
of fundamental power to harmonic and noise power. Modulation SINAD is the
reciprocal of the modulation distortion provided by the Modulation Distortion
measurement. This is another way to quantify the quality of the modulation
process.
Measurement Technique
Modulation SINAD is defined as:
Equation 2-5
where: P
total
= the power of the total signal,
P
signal
= the power of the wanted modulating signal, and
P
total
- P
signal
= the total unwanted signals which include harmonic
distortion and noise.
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
total
, the peak power of the
modulated signal is computed as P
signal
, the square root of the ratio of P
total
to
P
total
- P
signal
is calculated. The result is the signal’s Modulation SINAD. It can
be expressed as dB.
dB
ModulationSINAD
20
P
total
P
total
P
signal
–
----------------------------
log
×
=
Содержание N9000B CXA
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