Test Procedures R&S SMU200A
1007.9845.82 1.34
E-12
Test Method "FFT Demodulation
(Option FS-K7)"
• The FM deviation and distortion are determined by digital signal
processing in the spectrum analyzer.
• Restrictions: At large deviations and low modulation rates the settabl
e
m
easuring time maybe insufficient to determine deviation (1 period
minimum needed) or distortion. At high deviations and high
modulation rates the settable demodulation bandwidth maybe
insufficient. Missing lines at the spectrum borders deteriorate the
result.
Settings on R&S FSQ
:
A
MPTD / REF LEVEL test level,
FREQ / CENTER test frequency
FMDEMOD,
FMDEMOD ON,
RESULT DISPLAY / FM resp. PM
DEMOD BW > 2 * (deviation + fmod) for FM,
DEMOD BW > 2 * fmod * (1 + deviation) for PM,
RANGE / DEVIATION PER DIV 0.5 * deviation
MEAS TIME 3/fmod
for distortion (up to 3
rd
harmonic)
RESULT DISPLAY / FM resp. PM / AF SPECTRUM
DEMOD BW > 2 * (deviation + 3.5 * fmod) for FM,
DEMOD BW > 7 * fmod * (1 + deviation) for PM,
MEAS TIME 16/fmod
FM Setting Uncertainty
Test Method
Spectrum Measurement (see chapter
"Test Methodes")
Measurement
Settings on DUT
:
RF
On
Level 0 dBm:
Frequency Modulation menu:
Source Internal
State on
Recommended settings
CF sw
eep
10
MHz, 250 MHz, 500 MHz, 812 MHz, 940 MHz, 1067 MHz, 1194
MHz, 1321 MHz, 1484 MHz, 2200 MHz, 4000 MHz, 6000 MHz with
fmod = 10 kHz, deviation = 100 kHz.
Deviation sweep
Measurement at CF 500 MHz, f
mod
= 10 kHz,
deviation 1 kHz to half of max. deviation in logarithmic steps,
4 steps per decade (1, 1.8, 3.2, 5.6)
Repeat measurement at 500 MHz with external modulation.
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