R&S
®
CMW 500 GSM Applications
GSM TX Measurements
Operating Manual 1202.3986.32 – 03 220
Pattern Trigger
In the pattern trigger mode the R&S CMW 500analyzes the modulation scheme of the
received bursts and searches for a predefined burst pattern. The trigger events are
generated at the beginning of the pattern and repeated according to the GSM frame
clock, even though the true burst pattern may have changed.
To use the pattern trigger as shown above,
1. Feed the GSM uplink signal to the input connector and perform the necessary
analyzer settings.
2. Open the "GSM Measurement – Multi Evaluation Configuration" menu.
3. Select "Trigger > Trigger Source: Acquisition (Internal)", "Trigger > Acquisition >
Mode: Pattern", "Trigger > Acquisition > Pattern: GMSK GMSK EDGE OFF EDGE
OFF OFF OFF".
4. Start the GSM Multi Evaluation measurement and observe the triggered frames in
the "Power vs. Time" diagram.
Possible Extensions
You can use various other multi configuration settings for fine-tuning your
measurement:
Select a suitable "Trigger Delay" to delay the trigger events (and thus the start of
the measurement) relative to the detected frame boundaries. This is advantageous
in gap trigger mode, if the gap is not located at the end of the frame.
Use the "Modulation View" pattern to measure only burst sequences with a
particular burst type and modulation scheme. This can be advantageous in
combination with a gap trigger or in combination with a pattern trigger, especially if
the burst sequence is not strictly periodic. See "Capturing GSM Burst Sequences"
on page 220.
8.1.1.10 Capturing GSM Burst Sequences
This application sheet describes the use of the R&S CMW 500 "Modulation View"
settings for capturing GSM frames filled with a particular burst sequence. The R&S
CMW 500 can detect and filter GMSK, EDGE and access bursts.
Appropriate "Modulation View" settings are essential for measuring frames with burst
sequences that the mobile transmits only occasionally, e.g:
SACCH frames and idle frames that the mobile transmits with a periodicity of 26
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