Rohde & Schwarz CMU-K20, Operating Manual

Page: 41 / 646

CMU-K20/-K21/-K22/-K23/-K24 Non Signalling Mode
1115.6088.12 2.7 E-10
Additional Information... Alternative Settings
and Measurements
... on Step 1
#
Analyzer/Generator menu
The Analyzer/Generator menu contains three with associated
hotkeys used to
•
Define the RF input signal path and the trigger settings
(Analyzer Level)
•
Set the CMU RF analyzer (Analyzer Settings) and de-
termine the RF input signal that can be measured
•
Control the RF generator (Generator) and define the pa-
rameters of the RF output signal generated.
'
chapter 4, p. 4.2 ff.
The Analyzer/Generator settings
are also provided in the Analyzer
and Generator tabs of the Con-
nection Control menu. See also
notes on Softkeys and hotkeys on
p. 2.11 .
The assignment between carrier frequency and channel
number is according to GSM specifications. As the CMU
simulates a base station, the generator signal corresponds to
the downlink (signal direction from the base station towards
the mobile station), the signal analyzed corresponds to the
uplink (signal direction from the mobile station towards the
base station). The channel/frequency assignment changes
accordingly.
The RF frequency can be set in multiples of 200 kHz. With an
additional
Frequency Offset , an RF signal with an arbitrary
frequency that is in the range supported by the tester can be
generated and analyzed. In general, the RF generator level is
set to be different for the used timeslot and unused timeslots.
The level of the unused timeslots is defined relative to the
level in the used timeslot.
Selecting a definite training se-
quence (TSC) or bit modulation or
transmission mode in the
Genera-
tor Modulation panel implies that
signals with these characteristics
are generated.
Selecting a definite TSC in the
Analyzer Settings panel implies
that only signals with this TSC are
analyzed.
$
Measurement and Generator State
The state of the Power/t Norm. GMSK measurement is indi-
cated in the corresponding softkey (measurement control
softkey) and above the output fields for the results. The state
of the RF generator is indicated in the
Generator – RF Level
softkey.
For ongoing measurements, the results in the output fields
are constantly updated. All measured quantities refer to the
current burst. The default tolerance template for the power
ramp is defined according to GSM specifications. For various
reasons, an output field may fail to show a valid measure-
ment result (indication "---"):
•
The analyzer settings do not match the properties of the
input signal.
•
The input signal is missing.
•
The measurement is switched off (OFF is indicated in the
softkey controlling the measurement).
The current options for the meas-
urement status are
ON (default)
and OFF . A third state, HLT , oc-
curs after a single-shot meas-
urement is terminated (see be-
low).
Once selected, the Power or
Modulation measurement can be
switched off and on again by
means of the toggle key
ON/OFF .
Generators may also be switched
on (state
ON) and off (state OFF)
by means of the ON/OFF key.
%
Max. Level
The autoranging mechanism adjusts the RF input path to the
applied signal. Alternatively, the expected signal level (for
GMSK-modulated GSM signals, the average RF input level
plus an appropriate margin of a few dB) can be set via Ana-
lyzer Level – RF Max. Level.
'
Chapter 4, p. 4.69 ff.
The permissible range Max. Level
depends on the RF connector
and the external attenuation
used.
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