Rohde & Schwarz 1138.4000, Service Manual

Page: 36 / 213

Manual Test Procedure Radio Unit R&S CRTU-RU
1140.0050.82 1.16 E-4
Noise measurement function.
Test
¾
Measure the phase noise at the specified spacing from the carrier.
TX Residual FM
Preparation: Test setup TX5, no external trigger.
¾
Connect spectrum analyzer or modulation analyzer to RF1.
Control:
¾
Set CRTU Radio Unit generator to the specified RF frequency.
Output level at RF1 –27 dBm, analyzer to specified center frequency, FM
demodulator.
Test:
¾
The residual FM with the specified weighting is measured.
TX Residual AM
Preparation: Test setup TX5, no external trigger.
¾
Connect spectrum analyzer or modulation analyzer to RF1.
Control:
¾
Set CRTU Radio Unit generator to specified RF frequency.
Output level at RF1 –27 dBm, analyzer to specified center frequency, AM
demodulator.
Test:
¾
The residual AM with the specified weighting is measured.
TX Carrier/Sideband Suppression, Max. Distortion
The modulation quality of the analog IQ modulator of the CRTU Radio Unit is measured.
Preparation
Test setup TX5, no external trigger.
¾
Connect spectrum analyzer to RF3 OUT.
Control:
¾
Set CRTU Radio Unit generator to specified RF frequency.
Output level at RF3 OUT, 0 dBm,
¾
Switch on RF generator with offset modulation, 300- kHz baseband filter,
¾
Set analyzer to center frequency f
c
= 1000 MHz, Span = 300 kHz / 3 MHz
Test:
The suppression of the carrier at f
c
is measured relative to the useful sideband
signal at f
c
+ f
mod
.
RX Power Meter (Frequency-Selective)
Preparation: Test setup RX1, RX2 (depending on level range).
Control:
¾
Set CRTU Radio Unit to desired RX frequency and level and Input in menu RF
ANALYZER/ GENERATOR .