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Making Measurements
Advanced Features
The beginning of the 0 sample bin will be between 0 and 75µS (bit 0 - 20) after the
trigger as the sampler runs asynchronously to the trigger. The last sample bin will
complete sampling between 450µS and 525µS (bit 121 - 142) into the burst.
The measurement processor discards the 0 sample bin. This effectively removes the
ramp-up overshoot. Each measurement is also RF Power Qualified to ensure only
valid bursts are measured. Measurements with a result below the qualification level
are discarded.
The remaining sample bins 1-5 are averaged for the displayed measurement result.
Each measurement is therefore based on a 375µS (102 bit) sampling of the burst.
A mobile which does not meet the amplitude mask and has erratic amplitude across
the burst could give erroneous results with this measurement algorithm. It is
therefore essential that mobiles first comply with the amplitude mask in
GSM Rec. 11.10.
Making
Synchronized
External
MeasurementsUsing
Triggers From The
Agilent 8922M/S
There are two ways of making a synchronized external measurement using triggers
from the Agilent 8922M/S:
1 Use the G_EXT_TRIG on the rear panel SYSTEM_BUS connector. See
Chapter 6, Connectors for a pin out diagram.
This is a separate trigger directly from the Protocol Processor. It is only
selectable from the SERVICE screen. Once set it will provide continuous
triggers on each frame. Caution must be used as this trigger can have up to a
0.75 bit error due to the 156/157 bit variance in timeslots.
(GSM Recommendations allow use of 156/157 bit timeslots instead of the
156.25 bit length.)
To use the G_EXT_TRIG signal:
Go to the CONFIG screen.
Select the SERVICE field on the right hand side of the screen.
Select the LATCH field and find the selection labeled:
‘g_ext_trig_enable’ (SERV:LATCH:SEL ‘g_ext_trig_enable’)
Enter a ‘1’ in the VALUE field. (SERV:LATCH:VAL 1)
Select the LATCH field and find the selection labeled:
‘g_ext_trig’ (SERV:LATCH:SEL ‘g_ext_trig’)
Enter the TIMESLOT and BITPOSITION on which you want the
trigger to occur.
Example: 432 hex is TIMESLOT=4 BITPOSITION=32 hex. The
maximum TIMESLOT=7 and the maximum BITPOSI-
TION=9C hex (Bit 0 - 157).